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July, 1940 NEWNES PRACTICAL MECHANICS 425

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426 NEWNES PRACFICAL MECHANICS July, 1940

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forbidden.

Mechanised WarfareT is more than ever apparent that thisis a war of technicians, engineers, and

scientists, and that it will be won, notby masses of men, but by masses oftanks and aircraft. This means that wemust have ample supplies of materialof which Germany to -day seems par-ticularly short. We are more fortunatelysituated in that respect, but it is not toosoon for us to consider the problem ofsubstitute or ersatz materials, for eventhough we do not run short, if we canaugment the supply by the productionof synthetic materials we shall help toshorten the war because such materialswill enable us vastly to increase ouroutput of the weapons of war.

The Final SockdolagerTHE tank, a British production, is

playing a mighty part in the Conti-nental holocaust, but whether it will beable to deliver the final sockdolager is amatter of conjecture. It is my view thateconomic warfare plays a much morevital part. If you can stop up the supplyof materials to our enemies you preventhim making the very machines you seekto destroy. Prevention (of manufacture)is better than cure, or destruction aftermanufacture. Fortunately for us, weown the largest Navy in the worldwhich is able to keep open for us portswhich ate closed to the Germans,whilst the undoubted aerial supremacyattained by our Hurricanes and Spitfires,ensures that sooner or later we shalldestroy Germany's existing stocks.That is a lesson, apparently, which theItalians have yet to learn, but learn itthey will.

The Tank'THE tank was produced during the

I last war, and actually got intoproduction in 1916. Thus, it is only24 years ago since we taught theGermans the rudiments of modernwarfare. Tanks were first used in theBattle of the Somme, and their appear-ance so hypnotised and paralysed theGermans that they fled in hysterical

PRACTICALECHANICS

Owing to the paper shortage "The Cyclist" is temporarily incorporated

Editor: F. J. CAMM

VOL. VII. JULY, 1940, No. 82

FAIR COMMENTBy the Editor

disorder. For example, only one of thetanks attacked the village of Gueude-court, and the Germans became sofrightened at the sight of it that theysurrendered at once. Within a shorttime 300 other Germans had beendestroyed. The German High Com-mand labelled them as military toys,but there can be no doubt that theyplayed a large part in the defeat ofGermany. They do not call them toysto -day. Now that the Germans have somany thousands of them, the thoughtoccurs that considerable use could bemade of the thousands of cars in thiscountry, lying idle as a result of petrolrestrictions and high horse -power tax,by converting them for war purposes. Ifthey were modified by suitable armour-ing and the fitting of solid tyred artillerywheels, and equipped with light guns,they could provide a most potent mobileforce of over half a million. Because oftheir high speed and manoeuvreability,they could defeat the tanks. Thissuggestion is no more fantastic thanwould have appeared a month ago thesuggestion that we should use rivercraft to evacuate our troops from Bel-

-=EIGHTPENCE A MONTH-With much regret we announce an increasein the price of this journal to 8d. The veryheavy increase in the cost of paper, as wellas rising costs in other directions, havemade the step unavoidable if the serviceto readers is to be maintained. The alter-native of a reduction ih the number ofpages would have meant both the sacrificeof several features for which the journal isvalued by its readers, and the loss of theservices of our specialist writers whosecontributions form such an important partof our work. We prefer to maintain ourservice and our features, knowing that ourreaders would endorse our decision. Wefeel sure that we can rely upon their loyaltyand understanding in our difficulties.

THE EDITOR

gium, yet such have proved to be mostsuccessful.

Inventor of the Tank-THE question often arises as to who

I invented the tank. The answer isthat it was not the invention of anysingle man, but an adaptation of theHolt Tractor. Many people claim tohave invented the tank, but the factis that a large number of designers wereengaged upon the adaptation of anexisting piece of machinery. Thepresent writer had as much to do withthe invention of the tank as anyone else,for he was engaged on its production.The suggestion that any one man couldhave invented it is, of course, absurd.The ability to design such a machinepresupposes that the designer had vastscientific and .technical knowledge aswell as more than ordinary engineeringexperience. Some of the claimants tothe invention of the tank have neverbeen trained as engineers, and are with-out technical knowledge.

Outwitting the TankHE original suggestion that we

I should produce a tank emanated, Ibelieve, from an Army officer, but itwas the Commander in Chief in Francewho, through his experts, drew up thespecification of the type of machinethey required. Mr. Winston Churchillformed a committee at the Admiralvwith Sir Tennyson d'Eyncourt aschairman, to consider the matter, andthey carried out trials with a numberof machines, such as steam -rollers andcaterpillar tractors.

We have no doubt that each countryis endeavouring to design a machinewhich will defeat the tank, for it is oneof the anomalies of modern warfarethat as soon as a new death -dealingmachine is produced someone producesanother machine by means of which itmay be rendered obsolete.

With our remarkable and almost in-exhaustable resources, there cannot beroom for doubt that our technicians willfind the means and the machines todefeat the foe.

428 NEWNES PRACTICAL MECHANICS July, 1940

A LAND BATTLESHIP "READY FOR ACTION

Tanks in modern WarfareA " Military Toy was what the Germans called the Tank whenit first Made its Appearance in Warfare Nearly 24 Years Ago

IT was during the latter part of the lastGreat War that tankswere first used inwarfare. These ponderously moving

forts had been secretly constructed bythe. British and were used on the Sommein September, 1916. It was one of thegreatest surprises of the war for theGermans when they first. saw these monsterscrawling slowly over hedges and ditches,spitting fire from their guns as theyadvanced. They were driven by petrolengines and with the conclusion of -the warin 1918 designers at once set to work todevelop the tank. Larger tanks were built,stronger armour plating was used and theywere made more speedy. More guns werecarried by them and to -day these steelmonsters are armed against everything but adirect hit.

Amphibian TanksIn 1931 an amphibious tank made its

appearance. made by Messrs. Vickers -Armstrong. It was able to travel at 40miles an hour overland; cruise at six milesan hour in water, and climb a slope of 30degrees continually and a slope of 45degrees for short periods. It weighed 2

tons 15 cwt.. was 8 ft. 10 in. wide, 13 ft.long and 6 ft. high.

Year by year the performance of thetank was improved and the present-daymonster is capable of traversing theroughest ground by means of its caterpillartracks and their weight and manoeuvrabilitymake it possible to smash down enemyearthworks and pave the way - for theattacking infantry. The British Armyemploys three types of tanks-light.medium and heavy. The light tank iscapable of travelling over the ground at 40miles an hour and has a crew of three. It isarmed with twin machine guns, can ascendan incline of 45 degrees and cross a 5 ft.gap. It weighs 41 tons and can negotiatean obstacle 2 ft. high. The medium tank,which weighs 12 tons, carries a crew offive and is armed with three machine-gunsand a three -pounder gun. It has a speed of20 miles an hour. can ascend an incline of45 degrees and negotiate an obstacle 3 ft.high. The tank can also cross a 6 ft.gap.

The heavy tank has a speed of 30 milesan hour and weighs 16 tons. It has a crewof six. can ascend an incline of 40 degrees

and negotiate an obstacle 3} ft. high. It isarmed with three machine-guns and a 3 -pounder gun and can cross a gap of 9 ft.

French and German TanksThe French enormous 66 - ton tank

easily dwarfs all the others and carries acrew of 12. It travels at only 12 miles anhour and is armed with a 3 -in. gun and fivemachine - guns. Their medium tank isslightly lighter and slower than the Britishand only carries a crew of three as againstour five. It is armed with one anti-tank gun and one machine-gun. The light tankweighs five tons, which is I ton heavierthan ours, has a crew of two and is armedwith one anti-tank and two machine-guns.

Little is known of the heavy Germanmachines so we can only give details oftheir light and medium tanks. The lighttank weighs 4 tons, has a crew of two andtravels at 35 miles an hour. whilst themedium tank weighs 12 tons, has a crew offour and travels at 20 miles an hour. Theguns .carried by the light tank are two

GERMAN TANKSLight

Weight: 4 tons. Crew of 2.Speed : .3.5 m.p.h. Armaments,:2 machine-guns.

MediumWeight: 12 tons. Crew of 4.Speed: 20 m.p.h. Armaments:I gun and two machine-guns.Little is known of the heavy tanks.

Two types of German tank. On the left is a medium and on the right a light tank.


FRENCH TANKSLight

Weight: 5 tons. Crew of 2.Speed: 25 m.p.h. Armaments:1 anti-tank gun or 2 machine-guns.

MediumWeight: 10 tons. Crew of 3.Speed: 15 m.p.h. Armaments:1 anti-tank gun and 1 machine-gun.

HeavyWeight: 68 tons. Crew of 12.Speed: 12 m.p.h. Armaments:1 3 -in. gun and 5 machine-guns.

machine-guns and the medium has one gunand two machine-guns.Tanks in Action

It is obvious that tanks fighting in massformation are far more effective than singleunits and it is in this way that the tanks'.offensive power can be brought to bear fullyon the enemy. The crew of the tank must behighly trained and ready for any emergency.They are trained to do running repairs sothat if the tank gets damaged going intoaction it may be possible for them to patchit up so that the machine may carry on withthe action. All tanks are equipped with wire-less telephony and wireless telegraphy.

When the German tanks go into actionthey work in conjunction with low -flyingbombing planes. The Germans have alsointroduced 'flame -throwing tanks operatedby troops swathed in asbestos. The flame -throwing apparatus consists of a long barrelthrough which is squirted flaming petrol.A Vulnerable Point

The track in a normal German tank con-sists of a light steel chain. This chain runsover a toothed driving wheel at one end anda similar toothed wheel at the other end ofthe track. Slack in the chain is taken up bythe second wheel which is movable. Fourwheels, separately sprung, and fitted withartificial rubber tyres carry the main weightof the tank. When travelling over a smoothsurface or along a road, the tank usually runson these wheels, as, in order to save wear onthe tracks they are removei. The Germanscall the artificial rubber Buna and ifthrough hard wear or enemy machine-guns the rubber is stripped off the wheelsthe "idler wheel" finds it impossible to takeup all the slack that develops in the tracks,and there is a tendency for these to rideoff the guides.American Tanks

America is using tanks which arecapable of travelling at 50 miles an hourand are manned by a crew of four. Theirarmament consists of two fixed thirtycalibre machine-guns, one fifty calibre

OneM.G.eachside

The French kg.. --ton tank.

A French light tank is shown on the left and medium on the right.

anti-tank machine-gun and one sub-machine gun. They can be controlled byradio by the commanding officer at hisobservation post.

They have also an all -welded armour-plated tank which is capable of very highspeeds. The tank weighs 10,000 lb. com-plete, and is 2,000 lb. lighter than thepresent conventional type U.S. Armytank. The machine carries one driver, amachine -gunner and a cannoner. Besidesmachine-guns, it carries an anti-aircraft gun.The Bren Gun Carrier

And finally we come to the Bren guncarrier which is a tank in miniature. It iscapable of high speeds and with its crewof three and gun can inflict heavy losses inopen country. Though the carrier has notthe tank's power to smash down largeobstacles, it can travel over very difficultground.

As is to be expected in warfare, as soonas a new weapon makes its appearance onthe field of combat, inventors at once setto work to devise a weapon to counter it.Tank traps and anti-tank guns have madethe tank a less formidable weapon thanmost people think. Battalions are formedwhose special duty it is to fight against tanks.They are armed with light mobile gunswhich fire a 2 lb. shell and have greatpenetrating power. The French also havean anti-tank gun which will pierce verystrong armour plating and is said to be veryaccurate at long range. There are alsospecial anti-tank rifles in use.

OneM.G.each side

BRITISH TANKSLight

Weight: 41 tons. Crew of 3.Speed: 40 m.p.h.Can ascend incline of 45°.Negotiates obstructions 2 ft. high.

MediumWeight: 12 tons. Crew of 5.Speed: 20 m.p.h.Can ascend incline of 45°.Negotiates obstructions 3 ft. high.

HeavyWeight: 16 tons. Crew of 6.Speed: 30 m.p.h.Can ascend incline of 40°.Negotiates obstructions 31 ft. high.80 ton tanks are now being builtbut no details are available.

Twin Machine Guns

3 Pounder Gun

British tanks. Aheavy tank is shownon the left, a mediumon the right, whilstthat shown aboveis a light tank.

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The ElectronMicroscope

The New Technique of SuperMagnification by Electrical Means

An early form ofoptical micro-scope; magnifyingpower about r50

EVER since scientists evolved theirtheories concerning the existence andstructure of atoms and molecules

they have always wistfully contemplatedthe fact that these exceedingly minute par-ticles of matter must for ever remaininvisible even under the most powerfuloptical microscope which could conceivablybe constructed, the reason for this beingthat these ultimate specks of matter areactually Smaller than the wave -lengths ofvisible light. For, by no imaginable opticalmeans can a particle smaller than a wave-length of light be observed by means oflight itself.

The smallest particle which is visible tothe naked eye is about 1/100th of an inch inlength or breadth. Below this size, allparticles are totally invisible to the averageunaided eye. Using an ordinary microscopewith average high -quality lenses, we canattain a magnification of about 1,000, andby very careful working with specialinstruments it is possible to increase thisdegree of magnification under favourableconditions up to as much as 2,500.

Ultra -microscopesThen, of course, there exists the so-called

" ultra -microscope," the details of whichare fairly well known. The ultra-microseopeis merely a special type of optical micro-scope which, instead of employing ordinarylight, uses ultra -violet light or even thestill shorter X-rays. When fine particles in,say, a colloid solution are examined throughan ultra -microscope by means of shortultra -violet rays obliquely applied, theparticles, being somewhat bigger in sizethan the very short wave -lengths of ultra-violet light, intercept some of the rays andthereby reveal themselves to the observeras shadows, or, in some special circum-stances, as bright objects on a black back-.ground.

Many wonderful observations have beenmade by means of the ultra -microscope, itbeing possible to observe particles of aboutthe dimension of 1/10,000th of a millimetreby this method. There are 25.4 millimetresto an inch, from which fact the reader willbe able to form some notion of the extreme" reaching " power of the best modern ultra-microscopic observation.

But still, even the ultra-mieropscope can-not hope to reveal directly the almostinfinitely tiny atoms which, when grouped

together as molecules, make up matter aswe know it. Consider, for instance, thehydrogen molecules, which are ordinarilysupposed to consist of two hydrogen atomsbound together by some powerful attrac-tive force. It would take some two millionhydrogen molecules arranged in a line witheach molecule just touching its adjacentcompanions to make up a row one milli-metre in length. Other molecules, particu-larly those of complex organic substances,such as the proteins and cellulose, are verymuch bigger than hydrogen or similar mole-cules. Nevertheless, they are all smallerthan wave -lengths of visible light and con-sequently we can never hope to observe

A modern electron microscope used for the super -magnification of bacteria. The cathode-ray electrontube is at the top of the instrument, the observationwindow or eyepiece being below

An ordinary opticalmiscroscope of asimple amateurtype. With thisinstrument a magni-fication of about 200times can be ob-

tained

them directly by means of an ordinaryoptical microscope no matter how powerfulsuch an instrument might be.

A New PrincipleOf recent years, however, an entirely new

principle of magnification has been evolved,which principle, although it will hardlypermit of our being able to observe indi-vidual atoms as they exist in particles ofmatter, may, nevertheless, render it possiblefor us to see some of the larger moleculesand the " lattices " or frameworks in whichatoms arrange themselves in crystals. The

electron microscope," several of whichinstruments have been experimentally con-structed within the last two or three yearshas, up to the present time, attained apractical magnification of as much as20,000, compared with which resolvingpower, the ordinary " x 1,000 " magnifica-tion of our everyday optical "high -power "microscopes appears as trivial as the slightoptical aid given by a simple spectacle lens.

The electron microscope traces its originto the realisation of the fact that undersome circumstances moving electrons couldbe used for, the production of magnifiedimages instead of light rays, these travellingelectrons being suitably deflected by elec-tric or magnetic fields just as ordinary lightrays are refracted in an optical microscopeby passing through a series of lenses.

Upon this principle-a fairly simple onein itself-the electron microscope dependsfor its action. Essentially, the electronmicroscope consists of a cathode dischargetube which forms a source of electrons whenactivated by a high -potential electriocurrent. The electrons are projected down-wards through a very small aperture oediaphragm -opening along the axis of ahighly -evacuated metal cylinder.

Ironclad CoilsThe electron stream thus produced is

passed successively through specially -con-structed ironclad coils which represent thecondenser, the objective -lens and the eye-piece of an ordinary optical microscope.Finally, the -electron stream is allowed toimpinge upon a fluorescent stream, uponwhich the produced image may be visuallyobserved, or, alternatively, it may impressits image on a photographic film or plate.


Let us now grasp clearly exactly how theelectron microscope produces its magnifiedimages. The ordinary microscope gives its" picture " or image by the absorption anddiffraction of light rays. When, however, astream of electrons passes through a thinlayer of matter, some of the electrons, asthey approach the individual atoms or mole-cules in the material layer, undergo achange in energy content and/or in direc-tion. Consequently, they are swung out oftheir original path very much in the samemanner as rays of light undergo a change ofdirection when they are made to passthrough a magnifying lens. It is upon thischange -of -direction of the electron streamthat the magnifying powers of the newelectron microscope depend. Since, how-ever, the individual electrons constitutingthe cathode stream are exceedingly minutecompared with the wave -lengths of ordin-

lit

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Tuberculosis germs magnified 1,000 times by a high -power optical microscope

ary light, and since they are much smallerthan even ordinary atoms, it followsthat by the utilisation of an electronstream for this type of " electrical magnifi-cation " we have a means by which it maybe possible for us actually to observe par-ticles of true molecular dimensions.

Not Yet PerfectedThe electron microscope is not yet a per-

fected instrument, despite the fact that itstheory has been fairly satisfactorily workedout. It suffers at present from a number ofdrawbacks, chief among which is theextreme difficulty of constructing the

Object

Observationwindow

Image plate(Photographic plate

- can he placed here)

Cathode tube

Anode

Condenser coils

Object,ve cods

Valve connectingto exhaust pump

Condenser, objective and projection (eyepiece) coilscorrespond to these components in an optical microscope

deflecting coils so that they produce a per-fectly symmetrical electrical field aroundthe central electron stream. If, of course,the electrical fields produced by the coilsare not perfectly symmetrical, distortion ofthe electron beam will be set up, and thiswill make impossible the attainment ofsharp and " critical " images. Another dis-advantage inherent, as yet, in the electronmicroscope, is the necessity of having theobject under examination in as " thin " acondition as possible. So, also, is the factthat the object under examination must heplaced in a high vacuum. Furthermore, itfrequently happens that the object to besuper -magnified in the electron microscopeitself becomes destroyed and even disinte-grated owing to the enormous electricalenergy of the high-speed moving electronswhich pass through it.

The cathode tube of the electron micro-scope necessitates the employment of apotential of 50,000 volts or even more. Itis a difficult matter to obtain a perfectlysteady pressure or voltage at this exceed-ingly high potential. If, however, theelectrical pressure applied to the cathodefluctuates even slightly, the emitted elec-

trons vary in their energy contents, whichvariation sets up distortions in the magni-fied images as seen on the fluorescent screenor produced on the photographic plate.The electron stream used for this electric -magnification is, indeed, even more proneto distortion and to the production offaulty images than is the beam of light rayswhich is utilised in the ordinary opticalmicroscope.

Imperfections in ConstructionsIt would appear, however, that the

present-day imperfections of the electronmicroscope are all ones of construction, andthat, with increasing experience and skill inthe making and usage of such instruments,results far surpassing those obtained atpresent will be forthcoming.

Up to the present time, the electronmicroscope has been employed for examin-ing the nature of very thin films of materialand for elucidating the structure of exceed-ingly minute bacteria. The electron micro-scope does not at present give the finedetail which is characteristic of high -quality optical magnification. Rather, itsmagnification is yet of the semi -shadowvariety. Still, it is capable of producing adegree of magnification far beyond thelimits of even the most powerful of opticalmicroscopes or ultra -microscopes, and thereis every reason to believe that, with furtherstudy, experiment and experience in thisdirection the electron microscope will pro-vide physicists and scientists generally withan implement which will enable them to dis-cern all but the very atoms themselves.

An electron -microscope picture. Bacteria 18,000 timesmagnified. The mottled background probably repre-

sents actual groups of molecules

New Oil -finding MethodAT a meeting of the American Institute

of Mining and Metallurgical Engineersin New York recently, a new and simplemethod of prospecting for oil by analysinga quantity of surface soil was described.Among the advantages claimed for thisprocess, devised by Mr. Herbert Hoover,junior, and Mr. Washburn, of Pasadena,California, is that it may disclose the pres-ence of oil as deep as 10,000 feet below thesurface.

The apparatus was described as a semi-circular tube through which the gas mixtureto be tested is forced by electronic bom-bardment past magnetic fields. Gases ofa certain molecular weight are curved alonga known arc by the magnetic field and madeto pass through slits into chambers, wherethey are gauged quantitatively.

Half a dozen different gases will take asmany different paths and be directed intohalf a dozen different slits, providing at once

a quantitative and qualitative analysis ofcomplete mixture.

The richness of the sample in the gasesindicates the richness and probable depthof the oil in the earth.

Emergency Winding GearMR. D. M. MOWATT, convener of the

miners' rescue station at Coatbridge,has invented an emergency winding gear forcollieries. It is claimed that the invention,which will be used in any emergency toprevent miners being entombed, can beoperated as quickly as the normal windinggear. It includes two emergency cages anda small pithead frame with winding -wheelattached. The equipment is mounted ona chassis and can be transported to anycolliery where winding gear might be dam-aged in air raids. The set would enable a

rescue brigade to bring miners to the surfacein a few hours:

Non -Stop Return AtlanticFlights

IF necessary, non-stop return Atlanticflights can become a reality in from

12 to 18 months, according to a report sub-mitted to the United States Congress byengineers of the National Advisory Com-mittee for Aeronautics. It is stated thatchanges in wing design and the finning "of engine cylinders will greatly increase therange, speed and efficiency of aeroplanes.It is predicted that the new streamlinedwing will reduce the air resistance by onethird and will permit speeds of from 450 to500 miles an hour. The speed and efficiencyof the engine, it is expected, will be increasedby about 300 per cent. by the " finning,"which is based on the principle that theengine becomes more efficient, the faster theheat is carried away.


Mine Layers At Work

Fig. 1.-The mine before laying.

THERE are three methods of laying amine-by seaplanes, submarines andsurface vessels. Seaplanes are used

chiefly for laying magnetic mines as des-cribed in last month's issue, whilst the sub-marines and surface vessels are used for theordinary type of mine. Briefly, the marinemine is cylindrical in shape and is keptbuoyant by means of an air -chamber. Italso contains a high -explosive apparatus fordetonating the explosive. Although thereare various sizes of mine, the average,ordinary moored mine is about 650 lb. inweight and contains about 350 lb. of highexplosive such as trinitrotoluol (T.N T.).

The air -chamber takes up about half ofthe interior, and as will be seen from theillustration of the mine, is fitted with anumber of " horns." There are generallyfive or six of these and each one encloses achemically filled glass tube The explosive isdetonated when the glass tube is broken andthe chemical released.

WEIGHTED eA-6LEWHICH CONTROLSDEPTH AT WHICH'MINE IS LAID:

How Under -sea Bombs are Constructed and LaidThe Connecting Cable

A cable connects the moored mine to a5 -cwt. metal " sinker." In Fig. 3 is shown amine and sinker immediately after beingdropped by the mine -layer. The mine hasparted from the sinker from which the moor-ing cable is being payed out. The length ofthe weighted cable appearing below the

TUBES CONNECTING THEACID CONTAINERS TO THEDETONATOR

DETONATOR

PRIMARY CHARGE

HIGH EXPLOSIVE CHARGE

sinker determines the depth that the minewill be moored below the surface of the sea.

The weighted cable on touching the seabottom automatically checks the pay -out ofthe mooring cable causing the mine to bedrawn below the surface of the water, asshown in Fig. 4. In Fig. 5 the mine is shownafter all the laying operations have beencompleted, and it is anchored to the sinkerat the pm -determined depth from the sur-face In the event of the mine parting fromthe mooring cable, the mine rises to thesurface, as shown in Fig. 6, and is renderedinoperative by reason of a device situatedabove the mooring shackle, as can be seenin the sectional drawing.

Floating MinesWith the drifting or floating mine, which

is similar in principle to the mine just des-cribed, the cable which connects the mine tothe sinker is cut and then rejoined with achemical substance which gradually dis-solves in sea -water. This enables the mine-layer to get well away before the mine

SOFT METAL HORNS COVERING GLASSACID CONTAINERS. ON BEING STRUCKTHE ACID' BY CHEMICAL ACTION

OPERATES DETONATOR

Fig. 2.-A partsection view of amine showing its

construction.

HERE IS SITUATED THEWHICH RENDERS

THE MINE I NOPERATIVE SHOULDIT BREAK AWAY FROM ITSMOORING CABLE

breaks loose, and in this case the mine is notrendered inoperative.

Sometimes a hydrostatic device is fitted tothe mine to keep it under water, even after ithas come adrift. The floating mine is con-sidered to be not so dangerous as the mooredmine, as the waves set up by an approachingship have a tendency to push the mine Outof the way.

Figs 3 to 6.-Three stages in the laying of a mine. If the mine accidentally comes adrift as shown on the extreme right, it is automatically rendered inoperative.


The foregoing method of mine -laying iscarried out by surface vessels, but with asubmarine a different technique is used. TheGerman U-boats can lay the mines whilstthey are still submerged. They can carry -about 36 mines and these are carried in tubes

OurWhistle While You WalkA NOVELTY cane which will be usefulTA in the black -out has been patented inthe United States. It is tubular and hasa plunger round which a helical compressionspring is closely wound. On the principleof a locomotive whistle which shrillyannounces its approach, this whistling canein the darkness should prevent the collidingof pedestrians. The same arrangementmight be incorporated with an umbrella.

To Prevent " Housemaid'sKnee

MAIDS, charladies, painters, and allI those who in the course of their work

have to bend the knee will be interested ina scrubber's scooter which has recentlymade its debut. Constructed of weldedsteel and fitted with four ball -bearingcastors, this knee rest will enable floors tobe stained, polished and washed with themaximum of comfort. It should contributeto the prevention of ," housemaid's knee,"the complaint which attacks those who areso often caught bending.

THE type of dart board at present in useI is entitled to be enrolled in the noble

army of martyrs. St. Sebastian, the patronSaint of Archers, is said to have been boundto a tree and shot at with arrows. The dartboard is the long-suffering target of in-numerable missiles. Each successful aimresults in a piercing of the board. Thelatter, made of soft material, is, as a con-sequence, not everlasting.

An improved dart board is the subjectof an application to the British PatentOffice. - All parts of the board that countfor scoring are loose or hinged, so as tofall out of position when hit by the dart.This will avoid the necessity of using asharp -pointed dart. The scoring parts,displaceable by a hit, are mounted in sucha manner that they can be restored toposition by blocks on a shutter slidingparallel to the surface of the target. Theface of the board is covered with greenbaize like a billiard table. A net catchesthe fallen darts. It remains to be seenwhether enthusiastic dart players willregard this new board as agreeably less tothe point.

To Buoy You UpI N theie troublous times the perils of theI sea produced by Nature have beengreatly intensified by human nature or,rather, inhuman nature. Consequently, anewly -devised safety swimming suit is veryapposite. There has just been patentedin the United States a one-piece swimminggarment having, attached to the back andbreast, portions which can be inflated.Other inflatable elements are in the front,rear and -sides of the legs. Valved means,accessible to the mouth of the wearer,enable him to force air into all of theinflatable parts.

or chutes, in the hull of the submarine.From here they are released one at atime.

Aeroplanes are also used by the Germansfor laying bubble mines. They are droppedfrom bombing planes by means of a para-

chute. An advantage with this type ofmine -laying is that mines can be laid in analready mined area without danger to theaeroplane. How mines are swept and putout of action was described in last month'sissue.

usy Inventors.By "Dynamo'

9

The Horse's DeignONE sequel of the rationing of petrol

is the return of the horse to the high-way; Old Faithful has staged a come -back.It is appropriate that, at this juncture, thereshould be made in our country an applica-tion to patent an improved bridle. The aimof the inventor has been to provide meansfor controlling animals which are difficultto manage. Some of these intractablecreatures are known as " pullers," and"dead mouths."

The information on this page is specially supplied to"Practical Mechanics" by Messrs. Hughes & Young(Est. 1829), Patent Agents of 9 Warwick Court, HighHolborn, London, W.C.1, who will be pleased to sendreaders mentioning this paper, free of charge, a copyof their handbook, "How to Patent an Invention."

Previous bridles have included thesnaffle, which is a simple and gentle kindof bit. There has also been a curbing bitconsisting of a bar which passes through thehorse's mouth alongside the snaffle bit, andlikewise a chain hanging below the animal'slower jaw. , With such arrangements, how-ever, there is caused continual pressure.This benumbs the horse's mouth and inter-feres with the intimate relationship whichshould exist between the hand of the rideror driver and the mouth of the animal.The object of the new invention is to remedythis defect while furnishing the same or aneven greater degree of control.

The bridle in question comprises a nose-band encircling the horse's head above thenostrils and having at each side a guidemember, through which slides a curbingrein. The ends of this rein are attachedto a chain or similar curb between the guidemembers and adapted to lie under theanimal's jaw.

This curbing device can be easilydetached, so that it may be removed orreplaced quickly. It can be carried in one'spocket or other receptacle of limited size.

Giving a Horse His HeadAPROPOS of harness for horses, it is

interesting to note that the minds ofmany Victorians were exercised upon thesubject of the bearing rein. This particularrein forced the horse to arch his neck inorder to add smartness to his appearance.Humane folks contended that it was cruel,inasmuch as it restricted the free move-ment of the animal's head. Equally goodpeople maintained that it was the tightnessof the bearing rein which occasioned thehorse discomfort and that a loose rein of thisdescription would not inconvenience theanimal. In fact, they affirmed that in thecase of an equine Weary Willie," who isapt at times to allow his head to droop,a medium bearing rein would prevent thislazy habit. And I presume that, whenpulling a load, the freedom of the animal'shead could be achieved by loosening therein.

An eminent clergyman of the eighteenthcentury, the Rev. John Wesley, made someilluminating remarks upon the manage-ment of a horse. This reverend gentlemantravelled more than 4,500 miles a year onhorseback over bad roads and sometimesno road at all. And he used to read ashe travelled. Yet he says that his horsepractically never stumbled. The secretwas that he threw the reins on the neckof the animal. And this method, inpreference to a tightly -held rein, Wesleycontended, prevented his steady steed fromfalling. Verily a stable horse.

Accommodating BedspreadsOWING to the advent of summer, the

eiderdowns on our beds are too warm.But these padded covers are frequentlykept in use for ornamental purposes, par-ticularly where a certain decorative colourscheme is desired. Consequently, at night,the eiderdowns are apt to be creased anddamaged through being folded back ortemporarily removed. But it is oftenfound that the entire removal of the coveris too drastic, and a light counterpane isnecessary.

Bearing these facts in mind, an inventorhas made an application for a patent inthis country for a bed -cover which willeffectually meet the case. According to hisinvention, a bedspread has a central bed -covering portion and valances at the sidesand the end. Across the central portionis a detachable panel and between this anda base sheet is a removable pad. As aresult, the bedspread can be suited to theseason.

The Electrocution of FliesTHAT tiny aviator, the housefly, is

circling over the bald pates of those ofus who guard the home front, or settlingupon our rationed joints. To demolishthe gossamer -winged raider an electrifiedscreen has been devised. It is easy toinstal in the door or window and willelectrocute the annoying pests. Thetransformer requires a normal inpUt offour watts. When the screen is withinreach of human beings or animals, a metalguard of light weight is available. Themanufacturer, however, states that thescreen affects injuriously only insects.

Paper Footwear

PAPERslippers for the shower bath and

for lounging have made their advent.With paper at a premium on our side of theAtlantic, one does not expect this footwearto become the vogue here. However, thesource of my information is America,where the value of paper has not approxi-mated to that of "dem golden slippers"about which the coloured coons used to sing.It is claimed for these paper slippers thatthey do not collapse nor disintegrate inthe shower bath. There are no sharp edgeswhich might cut the feet. And they do notslip on any kind of floor, as non-skid spotson sole and heel allow sure gripping.


A ROCKRecent Tests Carried

' Out in America Witha Rocket Mail PlaneHave Proved Successful

AMERICA'S first air mail rocket,"Gloria," although covering only afew hundred feet in a recent test

flight at Greenwood Lake in New Jersey,may in time be considered as significantas that first historic flight of the Wrightbrothers at Kitty Hawk, which covered aneven shorter distance.

Despite the short distance covered, therocket mail flight has been termed a successbecause it proved certain basic principlesimportant to the world wide researchprogramme. It proved a rocket motor canlift and propel a loaded aeroplane fifty -

times as heavy as the motor itself. It also

proved a rocket aero-plane can maintain asafe stability whilst in.the air. From the firstflight it appears that theprinciple of the reactionmotor is basically sound,although it can standimprovement.

Design of the RocketPlane

The " Gloria " wasan undertaking of theRocket Aeroplane Cor-poration of Americawhilst the aerodynamic design of thewings and fuselage was the contributionof the Guggenheim School of Aeronautics.Loaded with air -mail covers addressed tostamp collectors the " Gloria " skidded to ahalt on the ice about 2,000 feet from thepoint of takeoff. The " Gloria's " two.pound motor actually develops 300 horsepower per minute. On the test block itregistered almost fifty pounds of re -actionon a measuring device. Propelling a 100 -pound aeroplane at a speed of about 4,000feet per second, the rocket motor woulddevelop an equivalent of 160,000 foot-pounds per second.

Whilst the motor is a hollow pipe with

ry MAIL PLANE

Rocket mail plane on a catapult ready for ta,,:eoff, and the tiny but powerful motor.

Carrying out final adjust-ments to rocket driven

mail planes.

no moving parts, its construction involvedmany difficulties. At present the maindifficulty in building a rocket motor isthat it is made of monel metal. When abetter heat -resistant substance is developed,there will be a great improvement in theperformance records of rockets.

FuelAnother important consideration at pre-

sent is fuel. After many disappointments,rocketeers have abandoned powder fueland substituted liquid fuels. Powderrockets create detonation waves whichcause dangerous explosions. Liquid fuellends itself to easier manipulation and

control, and is safer to handle. The" Gloria's " motor burned a mixture ofpowerful fuels blended in a combustionchamber. Fuel tank No. 1 containedliquid oxygen, temperature about 200degrees centigrade; tank No. 2 containedmixture of alcohol, petrol, methae andother liquids; tank No. 3 contained com-pressed nitrogen gas. The nitrogen gavethe necessary pressure to the other tanks.

As the liquids from tanks 1 and 2 aresprayed into the combustion chamber,they explode with a terrific impact. Thesudden combustion generates a hot gashaving a volume many thousands of timedthe original volume of the fuels. The pres-sure of the escaping gas lifts the rocketagainst gravity. Theoretically, the" Gloria " was supposed to build up herspeed until she reached a maximum of500 miles per hour. This is a long way fromthe speed required to escape the earth'sgravitation -25,200 miles an hour.

High -Speed CommunicationRocketeering experimenters are not

especially interested now in exploringouter space. They want, first, to builda rocket that will be useful for high-speedcommunication in comparatively low alti-tudes. Such rockets would be useful insending mail to remote and inaccessibleplaces. Military tacticians see still otherpossibilities. A rocket might be made intoa flying projectile with its own power -generating plant. It would fly faster thanthe fastest aeroplane and escape anti-aircraft attacks. For obvious reasons, boththe aeroplane and the balloon are in-efficient above 40,000 feet, but the rocket


motor operates better in a vacuum than atlow altitudes.

With the rocket motof, there -is no wasteof energy in the transmission of powerthrough shafts, gears or drives. For thefirst time, man has found a means of gettingpower direct from the heat of combustion.That is the principle of the reaction motor,and it is likely to find many useful appli-cations in the future. Theoretically, atleast, rocketeers have gone far. One hasalready designed a rocket aeroplane witha propeller. The combustion chambersare contained within the propeller blades.They have also studied the possibilities of

man -carrying rocket aeroplanes. A 150 -pound man in a 250 -pound ship wouldrequire fifty pounds of rocket fuel for aneight mile flight.

Air Travel by RocketsA vista of what air travel by rockets

may be like fifty years hence has beenopened by the patent of Prof. Robert H.Goddard, a Clark University scientist, whohas been experimenting for years at Roswell,N.M., with funds supplied jointly by theCarnegie Institution of Washington and theDaniel & Florence Guggenheim Foundation.

The Jekyll -Hyde aircraft, as described

in the patent, would change its shape froma conventional aeroplane at lower altitudesto a streamlined rocket ship when therarefied stratosphere is reached. In thetroposphere, the layer of air immediatelysurrounding the earth, the rocket aero-plane has wings, propellers, a tail skid,landing wheels, rudder and other conven-tional parts. In the stratosphere and above,only stubby wings are left.

Instead of being driven by propellersat these high altitudes, the rocket ship ishurled along by jets of gases streaming athigh speed from nozzles in the tail.produced from General Knowledge.

Two types of chlorination plant. (Left) Pressure feed. (Right) Automatic gravity feed.

DURING recent years considerableadvances have been made with thedisinfection of sewage and sewage

effluents as well as general industrialeffluents, using chlorine gas. This is idealfor the purpose, and one of the most import-ant benefits is the elimination or greatreduction of foul smells from decomposingorganic matter, largely caused by the evolu-tion of sulphuretted hydrogen. Chlorinecombines immediately with the latter,liberating free sulphur and preventing thesmell from this source. Equally importantadvantages of the chlorination of sewageand sewage effluents are the effective con-trol of the fly nuisance in summer and theprevention of the troublesome slimy algoidgrowths on the filters, which cause also thetrouble of " ponds " of liquid on the surfaceon the beds due to non -uniform penetration.

ChlorinationThe chlorination is carried out in the

settling tanks or other portion of the equip-ment before reaching the filters, whilst stillanother advantage is the prevention offoaming in the tanks. In this connectionthe " Chloronome " equipment of the Pater-son Engineering Co., Ltd. of London(Windsor House, Kingsway, W.C.2), one:ofthe main pioneers of the use of chlorine gasfor water, sewage, and effluents, is beinglargely used. Essentially this apparatus, itwill be remembered, consists in basic prin-ciple of a cast aluminium panel fitted withcontrol valves, narrow -diameter flexible

copper tubing coupled to a cylinder or smalldrum of liquid chlorine, pressure gauges,metering device, filter moisture seal, andtwo pressure reducing valves operating inseries. By means of the latter the chlorinegas always discharges to the apparatus aone uniform low pressure, generally 10 lbs.per square inch, irrespective of the highpressure in the cylinder or drum, whichvaries as the latter empty themselves.

The chlorine, adjusted in supply asrequired by the control valves, then passes

KillingBacteria

The Use of Chlorine Gasin most of the designs into a small waterabsorption tower forming part of the appar-atus, which is in the form of a verticalnarrow diameter cylinder of glazed earthen-ware, carrying the panel, so that a relativelyconcentrated solution of chlorine in water isformed and passed to the bulk supply ofeffluent or water as so to ensure uniformand rapid chlorination.

Types of MachineA number of different types of machine

are, however, available, including smallunits having a capacity of up to 10 lbs. ofchlorine per 24 hours, whilst a special verysmall portable set is also provided, carriedabout as required by one man. This isparticularly valuable also for the sterilisa-tion of drinking water, incidentally of greatimportance in war.

Equally important is the chlorination ofsewage and industrial effluents, therebyrendered harmless before discharge to riversand streams, generally requiring about two('parts of chlorine per 1,000,000, or slightlyover, but depending upon the conditions.Ordinary effluents from sewage works, forexample, frequently contain large counts ofbacteria which cannot be discharged direct,whilst river conservancy authorities all overthe world are quite rightly insisting upon amuch higher degree of bacterial and otherpurity of effluents, since more and moredemands are being made upon rivers fortowns supply.

An Aircraft that HoversABLENHEIM was returning over

Germany after a successful bombingattack on an enemy bridgehead when

the pilot sighted an unfamiliar type of air-craft flying low along a deep valley.

Diving at more than 300 miles an hour,the Blenheim pilot attacked with his frontgun, opening fire at about 35 yards.

" To my amazement," the pilot reportedafterwards, " the enemy aircraft appearedto stop and stand still in mid-air, forcing meto over -shoot."

Pulling out of his dive the R.A.F. pilotsought to renew the attack, but the enemyaircraft was now flying so low that thesteepness of the gorge prevented furtherattack.

The mystery of this " hovering " aircraftwas solved later, when the Blenheim pilotidentified it from a photograph as a Fieseler

" Storch," a German trainer -type aircraftwhich has such extensively slotted wingsthat it is endowed with remarkable slow -flying qualities.

Its proper name is Fieseler Fi 156, and itis used sometimes for army co-operationwork, especially for observation, forwhich its low speed makes it eminentlysuitable.

This aircraft was evolved from a numberof successive types built by the Germanfirm of Gerhard Fieseler Werke, founded byHerr Gerhard Fieseler, the acrobatic pilotwho designed the earlier models especiallyfor his aerial displays.

Although the Fieseler Fi 156 has a topspeed of something like 110 m.p.h., itsminimum speed is only 31 m.p.h. A speedthat is definitely " hovering ' comparedwith normal modern speeds.


MASTERS OF MECHANICSNo. 58.-Otto von Guericke, Inventor Of The Air Pump And

Investigator Of Atmospheric Pressure" ATURE," observed the philoso-

phers of old, " abhors a vacuum."But why this supposed natural

antipathy to a vacuous space should besuch a prevailing one, the few scientificthinkers of the age of Galileo entirely failedto explain.

Even the famous Galileo himself, whenconfronted with the fact that water could beraised by suction up a tube to a maximumheight of 30 ft. had to admit himself beatenwhen he was asked for an explanation ofthat fact. His rather lame answer to theforegoing query was to the effect thatwhilst Nature truly abhorred a vacuum, sheapparently only abhorred it to the extent ofa column of water some thirty feet in height.Which, of course, as Euclid had remarkedsome couple of thousand years previously,is absurd.

It is very easy for us moderns to visualisethe fact that we live at the bottom of anocean of air, just as much as deep-seafishes and other creatures have their exist-ence at the lowest ocean levels. And, in thelight of our knowledge, we find little diffi-culty in comprehending the sometimesstrange effects which our life at the bottomof the earth's enveloping blanket of air isoften fraught with.

We know nowadays why, under normalatmospheric conditions, a column of mer-cury some thirty inches in height will standupright within a vertical tube withoutflowing downwards from the tube into anunderlying reservoir or container. Thiseffect, the basis of the barometer, is causedby the downwards pressure of the atmo-sphere on the mercury. If such a mercurycolumn be set up on the top of a highmountain where the air pressure is less, itwill be found that the mercury column willdecrease in height, and if, of course, bymodern means, we remove the air from theexternal surface of the mercury in thereservoir, the column will collapse, therethen being no air pressure to support it.

AirAir, to our scientific forefathers, was an

intangible and, to a large extent, a some-what unreal entity. No one in the oldendays suspected that air could be dealt withvery much like water, that it could be com-pressed, expanded, made to flow alongpipes, and even, indeed, actually weighed !And so, not being able to grasp the essen-tially mechanical nature of air (or of steamor gases, for that matter), early experimen-ters found themselves very much handi-capped when they came to offer explanationsof certain natural effects. Moreover, theirinability to conceive air as being an essen-tially material medium severely militatedagainst their progress in the mechanicalarts.

Otto von Guericke, the famous and some-what romantic Burgomaster of Magdeburg,in Prussia, goes down in history as the firstman who successfully applied himself to thesystematic elucidation of the nature Of airpressure and as the individual whose workexploded the old superstition regardingNature's supposed dislike of a vacuum.Guericke, a somewhat universal genius andan apparently indefatigable experimenter,has also earned deserving fame for himselfas the inventor of the first electrical machine,

Otto von Guericke

which took the form of a rotating globe ofsulphur making frictional contact with apad of silk or similar material. Guericke'selectrical exploits, however, do not properlyconcern us here. Such we must reserve fordiscussion in a future series of articles onelectrical pioneers.

Guericke's FameThe bulk of Guericke's fame rests upon

his discovery of the air pump and upon hisrealisation of the fact that air is very muchlike water in many properties and that itobeys the same laws of pressure. Theexperiments of von Guericke, which beganin the middle of the 17th century paved theway for the coming of steam power, via the" atmospheric engine " of the early part ofthe following century. For the atmo-spheric engine " of Newcomen and otherinventors was, as the reader will, no doubt,

A modern laboratory air pump

recollect, worked by the downwards pres.sure of the air upon the upper surface of alarge piston operating within an open-endedcylinder. All that the steam was employedfor in the " atmospheric " type of enginewas to create, by condensation, a vacuum

underneath the giant piston, whereupon thepiston itself was rammed down in thecylinder by means of the air pressure on it.

As we have remarked, the " atmospheric "engine was the eventual outcome of Ottovon Guericke's work. So, too, was thelaboratory air pump of Robert Boyle, withwhich we have already dealt in this seriesof articles.

As regards Otto von Guericke himself, hewas born in the old city of Magdeburg onNovember 20th, 1602. Of a clever andingenious disposition, we find that he firststudied law at Leipzsig University, and thatsubsequently he took up the subject ofmathematics with much gusto, his aimthereby being to qualify himself for certainmechanical studies which he intended toembark upon.

Stayed in England and FranceGuericke stayed for a while in France,

and it would seem, also, that he resided fora period in England, although little or noth-ing is known concerning his activities in ourcountry. Neither Sir Isaac Newton norRobert Boyle were born at the time Guerickecame to England, and we can only surmisethat he visited our country for the sake ofenlarging his education generally ratherthan coming to our shores on some definitemission. At any rate, after his return toGermany, von Guerteke settled for a time atErfurt, a town in Saxony, and followedtherein the occupation of " master engineer "-probably of some mineral mills.

Some time before the year 1627, however,he had returned to his native town ofMagdeburg and had settled there, for in theyear above mentioned we have a record ofhis being elected a member of the Senate (orTown Council) of Magdeburg. Subsequently,he became (at the age of 50) Burgomaster orMayor of Magdeburg, and it was during histerm of office in this capacity that he con-ducted the pioneering experiments whichhave made his name famous.

The Italian, Evangelista Torricelli, a con-temporary of Guericke, had discovered theprinciple of the mercury barometer, andhad thereby demonstrated the materialityof air in supporting the mercury column.Von Guericke showed great interest in thework of Torricelli. As a result, he flunghimself into the task of trying to devise amachine which would extract air fromclosed containers and thereby prove that avacuum was possible, despite Nature'saccredited dislike of it.

A Crude Air PumpRealising that air could be treated like

water, he devised a crude form of air pumpcomprising a plunger cr piston workingwithin a metal barrel. With this implementhe attempted to extract water from a closedcask full of the liquid, but he found such atask to be almost impossible. Despite theexertions of two or three strong men, thepiston of the pump could not be drawn out-wards% in order to enable the water in thebarrel to be sucked out. Guericke, whose


idea had been to extract the water from thefilled cask, and thereby to leave the barrelfull of nothingness," quickly grasped thefact that the external pressure of the air onthe pump piston prevented it being drawnoutward. As our own Robert Boyle, the

First of the English Chemists," after-wards remarked, there is a spring in the air,which makes it resist forces very much likea spring of coiled metal.

By great efforts, however, Guericke didactually extract some of the water out ofhis closed casks, but having done so, hefound that such experiments wereall to no ;purpose, for immediatelysome of the water left the casks thesurrounding air leaked rapidly intothem through the pores of the wood.

By using metal containers, how-ever, Guericke found it possible toexhaust them of air, using for thepurpose- an improved air pump ofhis own construction. With theseexhausted metal containers he:gavea number of startling and specta-cular demonstrations.

A DemonstrationOne of these demonstrations, for

instance, consisted in joining to-g ;ther the two hemispherical halvesof a copper globe, the opposing rimsof the two hemispheres being separ-ated by a thin washer of oiledleather in order to allow of a betterair -tight joint being made. Througha small stop -cock screwed into one ofthe joined hemispheres, the copper globeor sphere was exhausted by means ofOtto von Guericke's air pump and theexhausted sphere was then suspendeddownwards from a strong hook. Attachedby chains to the lower hemisphere of thecopper globe was a platform upon whichwere placed many heavy weights. Despitethe load on the platform, the two hemi-spheres of the copper globe remained infirm contact, being, of course, maintainedin that, condition, as von Guericke himselfplainly realised, by the external pressure ofthe air. As soon, however, as the stop -cockwas opened, thus admitting air to the interiorof the globe, the lower hemisphere, with itsload. of weights, dropped instantly to theground.

In another spectacular demonstration ofGuericke's, a team of men attempted to pullasunder the two halves of the exhaustedcopper globe. Here, again, however, therewas no result until the stop -cock in one ofthe hemispheres of the globe was opened.whereupon the human team fell at once tothe ground !

Magdeburg Hemispheres "Of all the experiments of Otto von

Guericke on air pressure, the most famousand the most spectacular was that of the

Magdeburg Hemispheres." These con-sisted of a hemispherically divided copperglobe, similar to the one described above.but considerably larger. These wereexhausted of air, and subsequently a teamof 16 horses was set to the task of pullingthe hemispherical halves of the globe apart.Eight horses were harnessed to one of thehemispheres and the remaining eight to theopposite hemisphere. The two horse teamspulled in opposite directions, yet theexhausted sphere resisted their exertionsand its two hemispherical halves remainedunited under the external pressure ofthe air.

This experiment, von Guericke.performedbefore a large crowd of interested spectators,inclUding one or two royal princes.

Always a bit of a showman, Guericke, atthe conclusion of his Magdeburg Hemi-

The

spheres experiments was wont to instructa very small boy to open the stop -cockattached to one of the copper hemispheres,whereupon, the air rushing into the globe,the hemispheres, fell apart almost of theirown accord.

The famous " Magdeburg Hemispheres "still exist in the museum of that town. Andalso are to be seen there the many curiousair and water pumps, casks, barrels, andother crude and cumbersome pieces ofmechanical apparatus by means of which theworthy Burgomaster first gave the world at

first vacuum pump. Attempting to extracta sealed cask filled with the liquid

large its practical demonstration of themechanical properties of air.

Water BarometerOn the side of his house at Magdeburg

von Guericke erected a " water barometer "consisting of a metal tube some thirty feetin height. The tube was closed at its upperend, but open at the bottom, at which placeit dipped under water contained in a cistern.The tube was filled with water exactly inaccordance with the example of the mer-cury barometer discovered by Torricelli.

Boyles' original air -pump, the first mechan-ical air -pump to bemade in this country.With his pump he madea large number of ex-periments upon the phy-sical nature and proper-

ties of air

and von Guericke's essential showmanshipimpelled him to float upon the upper surfaceof the water in the tube a diminutivehuman figure, which, of course, rose and fellaccording to the downwards pressure of theexternal air on the water in the cistern.Such was the world's first public barometer.

Otto von Guericke was the first to give aproof of the materiality of air. He weighedone of his copper globes, using for the pur-pose the most accurate pair of scales whichhe.could command. Then he exhausted the

tattler from

sphere of air and weighed it again. Thedifference in the two weights represented,of course, the weight of the air extractedfrom the globe. In this mannermanner definiteproof was first afforded of the measure andweight of the air.

In another domain of practical science.von Guericke showed that heat was capableof making air expand and that cold wouldcause a quantity of air to contract. Hemade a number of thermometers, whichconsisted of large globes containing air.which, by means of a piston device, operated

a string passing over a pulley. Asmall human or other figure attach-ed to the end of the string mani-fested the expansion or contractionof the air within the globe bymeans of its movements.

The above, of course, did notconstitute 'a true thermometer orheat -measure. since von Guericke'sbulbs were also operated by thevarying pressure of the atmosphere.Nevertheless, it added furtherevidence to von Guericke's dis-coveries concerning the materiality,weight, and mechanical pciwer ofthe air. Indeed, our very ultra -efficient high-speed internal com-bustion engines are. viewed inone light, merely developments of.von Guericke's glass bulb ther-mometers," for they operate bythermal expansion and their fund-amental principle of power derived

from thermal expansion is the same as thatutilised in an infinitely gentler manner bythe energetic Burgomaster of Magdeburg.

Large-scale ExperimentsVon Guericke, it would seem, generally

devised his experiments on the largest scale.possible. A water barometer 30 ft. in heightpossibly appealed to him much more than a30 -in. mercury barometer. So. also, didteams of horses and men fruitlessly endeav-ouring to pull apart the component sides ofhis exhausted globes.

It was from Guericke's experiments thatRobert Boyle, of England, took his cue, andfrom the worthy Burgomaster, too, the earl-iest of the steam-engine experimentersderived their inspiration.

Von Guericke, it would seem, neverclearly grasped the fact that just as aircould be dealt with like water in many of itsproperties, so, also, could steam be treatedlike air in regard to its essential thermalexpansibility. Had he had any inkling ofthese fundamentals, one may depend uponit that the Burgomaster would have turnedthem to something spectacular.

His DeathIn 1681, von Guericke, having held the

office of Burgomaster of Magdeburg forsome thirty-five years, resigned it and wentto live with his son at Hamburg. in whichcity he died in 1686, at the age of 84.

Otto von Guericke was one of the world'searliest practical experimenters and mechan-ical constructors. As we have alreadyrecorded, his work gave inspiration to many.and it still forms a perennial source ofinterest to those who have the leisure todevote to his strange and curious writings.

In 1672, a decade before his retirementfrom active work, Guericke published hiscurious and entirely fascinating book, fromwhose illustrations the pictures accompany-ing this article are chosen. The book isentitled " Experimenta nova Magdeburgicade Vacuo Spatio." The work is excessivelyrare, but it is still to be come across in somepublic libraries, and it is well worthy ofexamination if only in view of its more thanordinarily interesting illustrations.


Modern Detonators andTheir Action

Explosives Have Their Peace Time Uses Equally as well asTheir War Time Applications

MOST or us are apt to connect theidea of explosives with that ofmodern scientific warfare Whilst

it is only too true that no country couldpossibly hope to successfully engage in warwithout an adequate supply of efficientexplosives, it is also equally true that veryfew modern industrial nations could makenormal progress in times ofpeace without the aid ofhigh -power explosives for thewinning of minerals and forother industrial purposes.

Explosives, therefore, havetheir peace -time uses equallyas well as their war -timeapplications, nowhere morethan in the sphere of blastingand explosive agents hasapplied chemistry made morespectacular strides during,say, the last half -century.

Curiously enough, the ex-plosives which are employedin modern times are byno means the most power-ful blasting agents known.Nitrogen chloride is a mat-erial which is very readilymade and which is far morepowerful in its blasting effectsthan ordinary dynamite orpicric acid. But substancessuch as nitrogen chloride arefar too sensitive to be of anycommercial application at all.Sometimes, indeed, they ex-plode almost spontaneously,say under the extremelyslight shock caused by a speckof dirt falling into them, orby their undergoing a sud-den rise in temperature.Obviously, therefore, suchexplosive agents, efficientthough they may be, are fartoo sensitive for any ordin-ary purposes and hence theirpowerful properties must perforceunutilised.

Fairly StableThe one common characteristic of com-

mercial explosives the world over is that,under normal circumstances, they remainfairly stable substances which only releasetheir main disruptive effects when compelledto do so by the action of an initiatingcompound which we call a detonatingsubstance or, more briefly, a " detonator."

A detonator has been aptly compared toa key or a trigger mechanism which servesto release the energy of a high explosive._All that the detonating substance does is togive a short, sharp shock to the explosivematerial, whereupon the latter, unable toresist the powerful although strictly localisedinfluence of the detonator immediatelyreleases its contained energy, thereby givingrise to the powerful explosion which ischaracteristic of it.

Exactly how the detonator exerts itsaction upon the relatively stable explosiveis even nowadays not known with anycertainty. Some chemists consider that thedetonating effect is simply due to thevibrational shock or " lines of force "which it creates in or around the explosiveproper. Others explain the detonator's

A rock

remain

face showing holes drilled ready for the insertion of dei

action by attributing it to the heat producedby the localised gas -compression which itcreates in the explosive material, whilststill other scientists consider that theactual sudden heat generated by thedetonator suffices to set the atoms of theexplosive proper into disruptive decom-position. No matter, however, upon what-precise principle the detonator acts, thereis no gainsaying the fact that if it werenot for the small number of comparativelystable detonating materials, modernexplosives could not be so extensivelyused, or, at the least, would only be ableto be employed with great danger to theusers.

The very first detonating material usedfor releasing the energy of high explosiveswas mercury fulminate which was firstintroduced in 1867 by Alfred Nobel, andwhich, until very recent times, has beenpractically the only detonating material incommon use.

onators

Lead AzideOwing; however, to the fact that supplies

of mercury are not always obtainable intime of war, several countries (particularlyGermany) have striven to discover a satis-factory substitute for this fulminate ofmercury. Such a substitute has beenforthcoming in recent years in the form of

a salt of lead-lead azide.It was found, however, thatlead azide was not quite soeasily ignited by a flame aswas mercury fulminate. Tomeet this difficulty, a materialknown as " lead styphnate "(which is the lead salt oftrinitroresorcinol) has beenemployed mixed with leadazide, and this admixture, itis found, will generally ignitewith the extreme ease ofmercury fulminate.

Silver azide is anothernewly -introduced detonatingsubstance. So, also, is (par.ticularly in America) a syn-thetic material known (atpresent) by its severelychemical name of " dinitroch-azophenol," which is a deriva-tive of ordinary phenol orcarbolic acid.

Now all these detonatingsubstances give rise to ashort violent explosion (or"detonation," as it is called)when either they are strucksharply (as in the case of thefiring pin of a rifle) or whenthey are suddenly heated orcaused to come into contactwith flame.

Whilst, as in the instanceof an ordinary rifle or guncartridge, we can so arrangematters that the impact ofthe rifle's trigger hammercauses a small amount of

mercury fulminate contained in the per-cussion cap of the cartridge to set thecordite within the cartridge into the stateof explosion and so eject the bullet, it isquite impossible to bring about thismechanical detonation in the case of ablasting cartridge or a high-poweredmilitary explosive.

In all such instances, resource is had tothe heating of a material (known as the" ignition composition ") which is placedabove the detonating material in theexplosive cartridge or shell. This beingdone either electrically or by means of anordinary slow -burning fuse.

Two Main ClassesDetonating devices nowadays can be

divided into two main classes, viz. " plain "detonators and " electric " detonators.

The ordinary detonator as used for insert-ing into the blasting cartridges used inmining and quarrying operations consists


merely of a tube made of thin drawnaluminium or copper and sealed at one end.The detonating substance (mercury ful-minate or lead azide or a special compoundof these or other materials) is carefullypacked by mechanical means into thebottom of the tube and above this is placeda little of the ' ignition composition "which is merely a material which ignitesat a relatively low temperature. Copper

OUTER SECONDARYCHARGE OF T.N.T.

pletion of the electrical circuit by means ofthe external switch arm or switch buttoncauses the fine wire within the detonator toglow. This at once inflames the ignitioncomposition, which sets the mercuryfulminate or lead azide into detonation,thus initiating the action of the mainexplosive.

Frequently, however, more complicatedtypes of detonators than'the above are

IGNITION COMPOSITION

SEALING COMPOSITION

INNER PRIMARY CHARGE OFFULMINATE OR LEAD AZIDE

Showing the make-up of the modern electric

acetylide usually fulfils this role of " ignitioncomposition," although, nowadays, it hasits competitors, like everything else.

The slow -burning fuse which consists of athin tube of some flexible material (e.g.,gotta percha) containing slow -burninggunpowder is inserted into the upper endof the detonator tube above the ignitioncomposition and is held securely andtightly in position therein by the simple" crimping or " nicking " of the upperend of the tube.

The detonator to which the fuse isattached is simply inserted into the primercartridge which is placed in the bore holes,further sticks of explosive are also placedin position after the primer, the hole isstemmed, and the fuse lit. The. resultantspark travels up the fuse, fires the ignitioncomposition which detonates the mercuryfulminate or other compound. The latter,of course, initiates the explosive reactionof the main charge.

In " electric " detonators, the principleof construction is not dissimilar from thatof the plain detonator, with the exceptionthat the slow burning fuse is omitted, itsplace being taken by a length of twin wireeonnected to a battery and switch at oneend and terminating within the detonatorin a very fine length of wire bridging twoelectrodes and itself surrounded by the cop-per acetylide or other ignition composition.

Electric DetonatorsWith such electric detonators, the corn-

wiaE BRIDGE

- detonator used in wiring and other operations

employed, it being found that if thedetonating charge of the detonator is -

divided up into a " priming " charge and amore powerful " secondary " charge it ispossible to set relatively very large massesof high-powered explosive into action withonly a single detonator.

Such detonators, therefore, contain :(a) the " ignition composition " of copperacetylide or some other material ; (b) the

THIN DRAWN ALUMINIUMOR COPPER TUBE

into action a " secondary charge ofT.N.T. or Tetryl, which latter brings aboutthe explosion of the main charge.

Thus, the explosion is brought about, notall at once, but in a series of steps, namely,sudden combustion setting up a detonation,the detonation creating a small localisedexplosion and the latter bringing about theenormous release of energy which resultsfrom the explosion of the main charge.

Although the ordinary type of detonatorhas the decided advantage of simplicityand robustness, such as serves well thepurpose of ordinary rock blasting, it is nowbeing out -numbered, even for peaceful andcommercial uses, by the electric detonator,whose detonation is consequent merelyupon the completion of an electrical circuit.

Coal MinesIn coal mining especially the electric

detonator is useful, since in fiery mines.the ordinary detonator used in conjunctionwith fuse which has to be lighted with auopen flame cannot be used. In recentyears, too, a special form of " permitted -electric detonator for coal mines has beendevised. This contains as the sealing -offcomposition a special variety of non-inflammable ehlornaphthalene wax, which,when the detonator and cartridge isshattered by the force of the explosion, doesnot take fire in the manner in which theformer sulphur compositions did and sogive rise to the risk of the burning sulphur

IGNITION COMPOSITIONCHARGE OFMERCURY FULMINATE

Diagram showing a- simple form of - plain - detonator used for exploding rock blasting charges

CRIMPED NECK OF TUBE

" priming " charge consisting of mercuryfulminate, lead azide or mixture of thesetwo and/or Other materials; (c) a " secon-dary " charge which may comprise a smalllocalised charge of T.N.T. ttrinitrotoluol)or " Tetryl " (trinitrophenylnitroamine).

Shells, bombs, mines, etc., which explodeon percussion simply have a nose capcontaining mercuric fulminate or otherdetonating substance. This, explodingupon percussion or friction, usually sets

SLOW BURNING FUSE

igniting any inflammable gases present in thecolliery workings.

Efforts at the improvement of thedetonator and at the devising of newdetonating materials are going on in allcountries. Waterproof, gas -proof, non-inflammable and many other types ofdetonators have been produced for special-ised commercial (to say nothing of military)purposes, but the ideal all-round detonatingdevice has yet to be found.

IRRIGATINGNew Canal and

I N order to irrigate the steppes of Stavropol1 a 31 miles long canal is being built. Inspite of the fact' that the abundant watersof the Kuban River flow through theserich and fertile steppes, there has alwaysbeen a shortage of water there. A 410 ft.ferro-concrete dam is being built across theKuban. Before starting this, an earthendam was constructed across the narrowpart of the river to direct the Kuban watersleftward into a new channel. When theferro-concrete dam has been completed, thewaters of the Kuban will again be directedthrough their old channel, yielding at leasttwo-thirds of their volume to the canal.Another dam, half a mile long, will beconstructed along the left bank, to preventthe river from turning aside. The canal will

THE STEPPESDams to be Built

run through a tunnel in the Nedremennaysmountain. This tunnel, which will be thebiggest in the Soviet Union, will be fourMiles long, 17+ ft. high and 16 ft. widb.It will allow for the passage of 962 milliongallons of water daily.

The new canal will irrigate 23,000 acresof land cultivated by the collective farmson the banks of the Egorlyk River, and

million acres of land in the Manychhollow. When the first section of the newsystem is in operation it will irrigate 111,000acres of land in the Orjonikidze region; over44,500 acres in the Rostov Province;50,000 acres in Kalmykia and more than17,300 acres in the Krasnodar Region. Thewaters of the canal will also be used forthe production of electricity. Two hydro-

electric power stations are to be built.These will be able to supply cheap power tothe industries of Voroshilovsk, Nevin-nomyssk, and Armavir. Four more powerstations are to be built later. It is expectedthat the Nevinnomyssk Canal will be com-pleted by the end of 1941.

Mechanical SalesmanIT goes without saying that efficient

salesmanship requires a considerableamount of talking. This can now be donemechanically, if a talking projector equalswhat is claimed for it. The machine is lightin weight and easily carried in a compactcase. Films are exhibited on a screenillustrating the article for sale and a recordedpersuasive description of the goods accom-panies the show. The projector is electric.ally operated. It may enable even a dumbsalesman to take orders.


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The I.C.S. have been giving a technical training through the post, inunsurpassed quality, for nearly half a century. We trained many thous-ands of men during the years 1914-18 and are splendidly equipped torender similar service throughout the coming months or years of thissecond Great War.

If you need technical training, our advice on any matter concerning yourwork anclyour career is yours for the asking-free and without obligation.Let us send you a booklet dealing with the subject in which you arespecially interested. It is packed with valuable information. DON'TDELAY. Make "ACTION " your watchword.

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ICS

4,12 NEWNES PRACTICAL MECHANICS July, 1940

Dr. R. Goranson, of Washington, D.C., with his "cascade bomb" with whichhe has created a pressure of 3,000,000 lb. per sq. in., claimed to be the greatestpressure ever to be created by machine. This feat was accomplished nt the

Geophysical Laboratories of the Carnegie Institute.

The Bofors GunTHE Bofors gun is designed to combat

low -flying enemy bombing attacks.The gun is very easily transported and hasconsiderable manoeuvrability. The fire poweris heavy and accurate. It is small comparedwith the 3.7 and 4.5 anti-aircraft guns,which are most effective against high -flyingaircraft. A stream of small high -explosiveshells are fired from it, each one capable ofdoing serious damage to an aeroplane. Inorder, to keep a high-speed, low -flyingbomber in focus the sights in the gun aremade very large. The gun can be trans-ported quickly over rough ground, and runson four heavy-duty balloon tyres.

New Farm ImplementsA DEMONSTRATION was recently car-

ried out at the Ford Motor Company'sfarm near London with some new types offarm implements for use attached to Fordtractors. The. devices were invented byMr. H. Ferguson, an Englishman, and areknown as the " Ferguson system." Thesystem consists of the attachment of farmmachines such as the plough, cultivator, andharrow, to a tractor by a simple arrangement)f bolts, and in such a way that implementand tractor form a single operating unit.Apart from reduction of costs, an importantadvantage of the new mechanical arrange-ment is that the attached plough or culti-vator can be lifted over an obstruction suchas a large boulder by a finger movementwhich the farmer performs whilst remainingseated on the tractor. The idea is to replace

horse with tractor equip-ment which could beused economically evenon small farms.

ParachuteTroops

T would appear that1 the German methodof landing troops bymeans of parachutes is atechnique that has beencarefully developed. Itis thought that Germanyhas four main parachuteschools and that a stan-dardised method is usedby the men for theiroperational descents.One of the chief difficul-ties with a parachutedescent is to land at apredetermined spot.

Air MinefieldsEEMY raiders may soon have the un-happy experience of running into a

minefield whilst in the air, as we learn thatan effective method of " sowing " the minesin the sky has now been devised. Inventorsare always thinking up some ingeniousweapon or counter -weapon to win the warand some of the latest discoveries beingdevdoped by Britain's scientific head-quarters are : " unsinkable." battleships;bombs which can be controlled by radio toexplode at a given signal; anti-aircraftrockets; heavy guns that can be flied byremote control and submarine tanks whichmay roll out of the sea on to an enemyshore.

"Flying Dark-rooms fl

NE of the latest war planes which willO soon be available to the Allies is amachine designed- for rapid reconnaissancework known as a " flying dark -room." The

THE MONTHOF SCIENCE

Wind strength has to begauged, and if a mistakeis made the parachutistwill land a considerableway from where he in-tended. The Germanusually jumps from aheight of 3,000 ft., butthey have jumped fromas low as 600 ft., whichis about the practical

limit. It is possible to "steer" the parachuteto a certain extent by pulling on the shrouds.In this way the parachutist can spill the airfrom one side of the parachute so that it willside -slip in the required direction. Withthe ordinary type of emergency parachute,the parachutist alights on the ground with animpact similar to jumping from an 18 ft. ,wall, but the German troops, with theirheavy loads of ammunition and equipment,use a larger canopy and therefore fall moreslowly.

New Piston Ring AlloyA NEW silico-aluminium suitable for

piston rings has been perfected inAmerica. Age -hardening constituents areincluded in its analysis and its use has ledto a considerable improvement of pistonperformance.

A Big Engineering FeatTHE engineers of the London. Transport

have recently completed one of thelargest and most difficult tasks they haveever undertaken. This is the modernisationof the Central Line which they started 3iyears ago. The chief difficulty was that thework had to he done outside traffic hoursand therefore the engineers could only work34 hours a night. The work necessitatedthe replacing of 10 miles of track, and to dothis they had to break up 20,000 tons ofconcrete, remove 1,500 tons of old rail and20 miles of longitudinal sleepers. Theythen had to instal 1,500 tons of new railand 27,000 new sleepers.

extensive equipment of these machinesenable photographers not only to takepictures from the air but to develop andmake prints from the negatives whilst theaeroplane is still in the air. Only fourminutes elapse from the click of the camerato the production of a well -processed print.Another advantage of these flying studiosisAthat the prints can be sealed in tubes anddropped direct to given objectives. Thus,photographs can be delivered without thepilot having to land for the purpose.

A New BridgeTHE bridge spanning the river Periyar at

Alwaye is now nearing completion, andwhen it is finished it will. have thelongest span in South India. It is claimedthat it will also be th,e widest bridge inTravancore.

Surface -HardeningMetals

A N interesting development in the metal -r -1 lurgical world is a small device, in-vented in Russia, for surface -hardeningmetals. It uses a gas pressure of 10 cm. ofwater, and by its means steels and non-ferrous metals can be given treatmentscorresponding to nitriding, carbonising,cyaniding and bright annealing. The in-vention comprises all the equipment neces-sary to give the requisite gas mixtures.

New Sparking PlugAN American tyre and rubber company

has developed.a new sparking plug inwhich polonium is used. Polonium is a rareelement which costs about £400,000 anounce. It is stated that polonium is so full ofenergy, that its equivalent of one gallon ofpetrol would drive a car 1,000,000 miles, ifit could be properly harnessed. Some of thisenergy applied to the air inside a sparkingplug maintains the air in constant readiness


for an electric spark. The ignition systemworks, with the first turn of the engine, asthough the engine had been previouslyrunning for some time.

Coalless SteelworksTHE president of the Iron and Steel

Institute, Mr. J. Craig, says that intime we shall have a coalless steelworks.He stated that there is a superabundance ofwater power in Scotland which could beused to develop the electric blast furnace.Raw fuel has been practically eliminatedfrom the steelworks, and coke -oven andblast furnace gas was now being used tomelt the steel and to raise steam to producesufficient electricity for all the plant" re-quired to finish the steel ready for themarket. He went on to say that he believedthat the abolition of raw coal even for thesteam locomotive was in sight, as thereappeared to be no reason why it shouldnot he fired with compressed coke -oven

iN THE WORLAND INVENTION

be remembered that the Germans have forsome time been experimenting with colouredsearchlights which are supposed to penetrateclouds more easily than the ordinary whitelight, but so far they have not proved verysuccessful.

New Bombing Invention

Steam -Driven PlanesTHE La Mont boiler is a controlled

circulation steam generator which wasinvented some years ago by an Americanengineer, Walter Douglas La Mont. It isextremely compact in design and usesnearly 50 per cent. less material than otherhigh-pressure steam generators. It couldthus be used for steam -driven aircraft.The La Mont Steam Generator, Ltd., intro-duced the La Mont boiler into this countryabout four years ago, and more than fortyboilers of this type are now at work inEngland. The London Power Companyhave one of these boilers, evaporating350,000 lb. of water per hour, at work intheir Deptford Power Station.

Hemp and ResinBicycle

ABICYCLE has been made at Allessan-dria, Piedmont, from hemp and resin.

It weighs about 30 pounds and can carry aweight up to 240 pounds and hemp andresin were used for practically every partof it. The experiment has proved sosuccessful that the Italians are consideringmaking other mechanical equipment fromthese strange materials. But if little Williewants to start making himself a bicyclefrom string and glue he must be gently butfirmly told that it will not work.

Flying SearchlightsTHE German Air Force have been experi-

menting with searchlights for aero-planes, the idea being to illuminate a bomb-ing area to assist aiming. It has also beensuggested that a fighter fitted with a smallsearchlight would be able to locate theenemy in the dark and then attack it. Theobvious objection to this would be that theplane fitted with the searchlight would alsobe exposed to attack, but no -doubt the beamwould dazzle the enemy's gunner. It will

I T is learned that William P. Lear, anAmerican radio engineer has perfected a

device to enable mass bombing raids to becarried out in weather conditions whichscreen the bombing planes from enemypursuit pilots and anti-aircraft fire. Mr.Lear who is an internationally -knowninventor, demonstrated his invention beforeAllied military experts. The device consistsof a radio set having a dial fitted with apointer which indicates from which directionradio signals are received, and a secondindicator which is " tied " to the NorthPole. A miniature gyroscope is fastened tothe second indicator, and this indicatorkeeps pointing in the same direction regard-

less of any turns an aeroplane may make.Thus, provided the pilot of a bomber knowshis direction and distance from a target, allhe needs to do is fly a given length of timeat a known speed and signal his crew torelease bombs when his watch indicates thathe has arrived. The test flight was extremelysuccessful.

Banana MealA CUBAN plantation manager has per-

fected a new process for manufactur-ing meal from bananas. This meal may be

combined with flour for making bread.The Cuban Minister of Agriculture estimatesthat enough meal could be produced bythis new process to establish an exportmarket.

New American PlaneEngine

DELEGATES of the American Societyof Mechanical Engineers in New

York, have been given details of a newfighter plane engine. This giant engine isestimated to be capable of attaining speedsof 400 miles an hour. It is described as a" new high-powered, liquid -cooled enginewith 42 cylinders."

Pipe Smokers'-Thermometer

THE claims that tobacco manufacturersmake about the coolness of their blends

can now be put to the test by pipe smokers.A new type of pipe is fitted with a midgetthermometer on the side of the bowl. Itcan be seen while the pipe is being smoked.

Electrically -driven TugsTHE Central Institute of Research in

River Transport in the Soviet Unionhave recently been carrying out experimentson the Ladoga Canal with the idea of pro-pelling canal tugs by electricity. It wasproved by experiment that wires stretchedalong the bank of the canal could supply thecurrent to drive the tugs. A special contactwagon which feeds power by cable to thetugs, has been designed by E. Yanovskaya,a woman engineer employed at the Institute.As the boat moves along the wagon slidesalong on wires. The usual method of pro-pulsion for tugs is steam or diesel engines,but the fitting of electric motors will mean aconsiderable reduction in the cost of thevessels, as well as lower overhauling andrepair costs. Moreover, steam power coststwice as much as the cost of electric traction.

All steel even to the tyres, this "Marsh Buggy," constructed by the Stanolind Oil and Gas Companyin their Dallas shops, is the latest thing for transportation and exploration in swamps or marshysections. The buggy will travel on dry land, water, or a mixture of both. The buggy itself weighs10,000 pounds and will carry a 6,000 -pound load. It is 2I feet long and 15 feet wide overall. The

wheels are huge, arc -welded steel drums, water -tight and buoyant.


We are indebted to thePostmaster -General forthe information arcillustrations container

in this article

The Teleprinter-HowIt Works

-PART 2

A front view of the teleprinter from the left-hand side

Receiving and SelectingThe electro-magnet is fitted at the right-

hand side of the machine as shown in theabove illustration. The unit consists of apowerful permanent magnet having lamina-ted pole -pieces, which are shaped so thatthey practically enclose the operating coilsand the armature. The armature, also con-structed of laminated soft iron, is pivotedat its centre, and is capable of smalllateral movement between the pole -pieces.

The Electro-magnet Link couples thearmature to a lever on the trip shaft andalso engages the starter -trip lever. The

Main Shaft.

Typehead Spindle

Receiving Cam Shaft Gearing

Retention Lever

Receiving Cam Shaf tRatchet Pawl

Retention Lever Spring

Receiving Cam Paw Abutment /

Trip Shaft..ectrornagnet

Link....... ...............

.Electromagnet Armature,-

Receiving Cam Shaft

Receiving Cam Sleeve

Setting Blade Lever

(Concluded from page 404 of Last Month's Issue)

means of one of them it is coupled to theelectro-magnet link. Through the otherlever it is connected to the receiving campawl abutment link. Two functions areperformed by the trip shaft : (a) To controlthe rotation of the receiving cam, by engage-ment and disengagement of the pawlsthrough the action of the receiving campawl abutment; (b) To guide the finger -setting blade, so that the correct selectionis made on the comb setting fingers inaccordance with the incoming signals.

In Fig. 7, T1, T2, T3, T4, and T5 are thereceiving cam tracks. T1 has five indents.

Type Hammer Lever

Type Hemmer Link

Traversing lever

Belkrank lifting Lever

BellcrankLiftingCollar

: .:.,- -\;.-- ---i --"::: ----...:,-...----. ...... ---CamTracksiii,;

Finger Setting Blade. ..... ...... ---.-*- ;-. --..... -).%*. af

Traversing Link - " - / '. wFinger Setting Pin Spring-"

Finger Setting Pin -.' /.:-.

Finger Setting BiladeGusies, ....001.,,,,i

..:.1 . Ribbon Feed Spinole..1....QC.. ; ...--4...:

movement of the armature in response Ribbon Feed Pawl -.....--*/%***:{Frithto incoming signals causes the link to finger Resetting Lint' i e

turn the trip shaft into one of two positions Comb Setting fingers!corresponding with the received signals.

The trip shaft, which is shown in Fig. 7, Receiving Comb 'Extensions : ;

moves under the control of the electro- Finger Resetting Belicrani,-: Imagnet armature in response to theincoming " marking " and. " spacing >'finger Resetting Trip Bell crank:

signals to either of two positions. This shaft Carriage Feed lever

carries two levers near one end and by

Comb \wog lever

' ......... FigweShiftBellcrank

-LatterShift Belicrank

........

tions which actuate the finger setting lever,which carries the finger setting blade. T2has only one indentation into which thetype -hammer lever rides and causes thehammer to strike the selected type. T3has a double bend in it which gives thetraversing lever a reciprocating movement.T4 has one indentation which actuates thebellcrank lifting lever. The one indentationin T5 actuates the comb setting lever, towhich the selecting fingers are linked.

There are five receiving combs which canbe seen in Fig. 7. Their purpose is to selectthe required bellcrank, or latch, which willcause the type corresponding to theincoming signal to be printed. They aremounted on a stationary cylinder, known asthe combination -head body, through thecentre of which passes the typehead spindle.The receiving combs are free to turn slightlyabout the cylinder, and are retained inposition by metal collars. Indentations arecut into the periphery of each of thereceiving combs. They are so arranged that,for every position into which the combs aremoved by the comb -setting fingers, a spaceis provided beneath one pair of adjacentbellcranks. One of the bellcranks of eachpair to a " letter " character and the otherto a " figure " character.

Turning again to Fig. 7, the bellcranklifting lever will be seen. During itsmovement inwards toward the combinationhead, it lifts the bellcranks, or latches, from

tSellcrank Fukrum orBearing

Bellerank Retaining Spring

.Bellcranks....Shift Comb

":.,-.....lx":Shof I Comb Lever (See C.I004. Fig. 10)

...Receiving Combs

...Typehead Clutch Drum .Typehead Sleeve

Typehead Clutch SlopTypehead Clutch Latch

..-'..Twehead Clutch Latch CamTypehead Hammer Spring

Type Hammerhead

--Ink Ribbon----Types...-Typebeed Bracket

Ribbon Jumper

:.%00, Ribbon Jumper--RestoringSprin9

Ribbon JumperShaft...... i I

'Finger Resetting Trip Bell crankAdjusting Screw

Fig. 7.-The receiving and selectingmechanism


the edges of the receiving combs. The bell -crank employed for the previously printedcharacter is withdrawn from engagementwith the typehead clutch, which commencesto rotate again. The receiving combs arerestored to their normal position by restor-ing springs. When the receiving combs arereset for a new character, by the selectingfingers pressing upwards on the receivingcomb extensions, the bellcrank lifting collarmoves outwards, allowing the bellcrank fora new character to be drawn into thelongitudinal slot prepared for it by thealignment of the receiving combs.

The Printing MechanismThe type hammer is actuated by the

Hammer Lever through the action of theHammer Link, and is held in its normalposition by a spring. In order to avoid thepossibility of damage to the type pads dueto the hammer being actuated during thetime in which the typehead is rotating, thetype hammer is pivotally mounted.

As previously mentioned, the ink ribbonmechanism used is similar to that of atypewriter. The ribbon is lowered after theprinting movement, so that each line ofprinted characters is visible to the operator.The ribbon is accommodated on two smalldrums.

If it is desired to change from page print-ing to tape printing, the teleprinter can bereadily adapted for this purpose. Theplaten is a rubber -covered metal rollerover which the paper is passed during theprinting operation. A rotary motion isimparted to it by means of the pawl actingon a ratchet attached to the platen spindlewhich passes through its centre.

The carriage is normally returnedmechanically by the action of the carriage

return mechanism. It can, however, bereturned manually by means of the carriagereturn key fitted at the left-hand of theunit.

When the " carriage -return " signal isreceived, the Carriage Return Control Leveracting on the Carriage Return Dog, raisesit into engagement with the clutch cross-head. The Pawl Throw -out Lever ispivoted near its upper end and its lowerend engages with a pin, fixed on the carriagerelease link. As the clutch cross -headmoves to the right, the bottom end of thethrow -out lever is deflected, and the upperend depresses the Feed and Retention pawls,disengaging them from the carriage springdrum. This permits the carriage springdrum to rotate and return the papercarriage to the right for the next line ofprinting. A shock absorber is fitted tominimise the shock of impact as thecarriage is returned.

Automatic Start -Stop SwitchWhen the " start " signal, which is in the

" spacing " direction is received, thearmature of the electro-magnet is movedand the spindle, which is free to movelongitudinally, is thrust by the startertrip lever against the tension of the thrustspring. This withdraws a weight -liftingpin from the worm wheel and the weightis allowed to drop forcibly on the switchoperating lever.

The " Answer Back " UnitIn order to enable the calling operator to

verify his connection with the " called "operator an " Answer Back " unit is fitted.The advantage of this unit lies in the factthat if the circuit at the distant end is un-

attended, messages can be transmittedwith the certainty that they are being sentto the correct subscriber.

The unit is brought into operation bydepressing the key, at the transmitting end,which is labelled, " Who are you ?" Adrum spindle is mounted at right anglesto the comb bars, and in close pFoximityto their right-hand ends. At the endnearest the comb bar assembly, the drumspindle carries thirteen rows of projectionsor wards fixed radially, like the spokes of awheel, and parallel to the axis of the shaft.The purpose of these is to engage withcertain of the comb bars. Each row ofwards is arranged to represent one of thesignal combinations to be transmitted whenthe unit is brought into action.

The driving gear wheel is driven con-tinuously through worm gear while themotor is running, and engages with a frictionclutch. . The drum spindle is preventedfrom revolving by the &tent which isnormally held in engagement with a notchin the drum spindle by the detent restoringspring.

When a " Wild are you ?" signal isreceived, the relative bellcrank or latch onthe combination head is drawn inwardstoward the centre of it, and the AnswerBack release shaft follows up the move-ment of the bellcrank. The detent is with-drawn by the pull of the release shaftrestoring spring from the notch in the" Answer Back " drum spindle whichthereupon begins to rotate.

The comb bars instead of being pm -setby the depression of keys as in normaltransmission, are controlled by the com-bination predetermined by the position cfthe projections or wards on the " AnswerBack " unit drum spindle.

Making A Tool CabinetA Portable Tool Cabinet

for EngineersTHE basis of all cabinets is the body,

consisting of back and front, top,bottom and two sides. The sides, top

and bottom are dovetailed together, andcare should be taken to arrange that thedovetail pins are on the top member forotherwise the box will pull apart whenlifted by the handle. Dovetails should beplain, cut at a bevel of 1 in 6 or 7, with ahalf -dovetail, which should be the fullwidth of a dovetail at each end. The sharpedges of the joints should be rounded off toa radius of '/E, in. at least.Size of Body

The size of the body will depend on thetools it has to contain, but minimum widthis 141 in. With % in. for thickness of sidesand I in. for thickness of drawer sides,this allows full - length drawers whichwill just accommodate an engineer's foot -rule, and are amply wide enough to take a12 in. protractor set, a 10 in. slide rule (incase) and a 10 in. vernier; which are usuallythe longest tools in the craftsman's kit.However, a 12 in. vernier calipers or height -gauge will necessitate drawers of 151 in.internal diameter, and sides of f in. stuff.It may be better to make separate cases forthe longer instruments than to increase thesize of the cabinet, unless fewer drawersand a body of 1 in. stuff are provided, when

a longer, but lower cabinetwill result. This latter vari-ation must be rememberedbecause it is all too easy tomake a cabinet that willhold so many tools that itwill be too heavy to carry.As a general guide, the sizeof the cabinet should notexceed one cubic foot, butthe width, depth and heightmay be varied, in any pro-portion within this.limit.

Number of DrawersThe depth and

number of thedrawers must nextbe determined,and, in designingthis portion of the cabinet, it is well todecide whether the drawers are to be onrunners with a rail between each drawer, orwhether the sides are to be grooved forsliders. This latter system allows a greaternumber of drawers, or drawers of a greaterdepth to be fitted, since no height is lost bythe insertion of a rail and runners beneatheach drawer. While this is excellent forshallow drawers, and is the usual practice intool -cabinet making, there are disadvan-

The appearance of thefinished cabinet.

/Slides

iOrawers

2Dr,zwev

3Drawer

Cages. Drawers so constructed must havesides off in. stuff; and it is usual to ploughout grooves in these sides to take the bottom,instead of " slipping " the drawer as inordinary cabinet -work. This makes anarrower drawer internally, or adds f in.to the width of the cabinet. Then thebottom must be of very thin plywood, andthis is not always advisable, especially whenit is remembered that the deeper ctrawerswill have to accommodate such heavy tools


Right Wrong

The right and wrong method of dovetailingthe top and sides.

as a surface gauge, angle -plates, a smallsurface plate and large parallel cramps.Fitting a Muntin

If this system is adopted, it would be wellto strengthen the bottom by fitting amuntin across the centre of the drawer.What is more, when the sliders wear, thedrawer drops, and binds on the one beneath.This fault often affects the sliding front,which is immediately beneath the deepestdrawer containing the heaviest tools. Witha drawer on runners and a rail, wear doesnot affect anything beneath and for thisreason, all .drawers containing heavy toolsshould be so constructed. So must rows ofsmall drawers, unless they are very shallow,when the division rail may have a sliderfixed on each side, and be fastened to thetop of the body by screws driven in fromthe underside.Size of Drawers

Except for one drawer, which should be21 in. or 3 in. deep, to take angle -plates andother larger precision tools, and another2 in. deep, to take the foot of a heightgauge, no drawer need be more than 1 in.deep internally. Indeed, this height canusually be reduced by making slides of 1 in.stuff, recessed out to take such tools as taps,dies (with wrenches and stocks), punches,small chisels, reamers and the like, whichform the bulk of the craftsman's kit, and -which are all too often shot haphazard intoa. drawer. So too with drills, which are oftenkept in utter disorder in tin boxes, whenfive minutes of ".milling up " is alwaysnecessary before the required drill can befound. Simple slips of wood, or mild steel,bored to take the drills with the sizestamped opposite to each, are great saversof time, and can be hinged on to the sidesand front of a drawer, or if preferred, justslipped in. This principle can be carriedfurther, and guides or recesses can be fittedin the drawers for every tool of importance,such as micrometers, verniers, sine -bars,precision squares and straight -edges. Theymay consist of blocks screwed to the drawerbottoms, or outlines of the tools can be cutin plywood, and similarlyfixed. For all such, velvetis better than baize asa covering. By fittingrecessed slides, 1 in. of

height is saved on every shal.low drawer, which may permitanother slide to be fitted, orallow for a rail and runners onthe bottom drawer, or thedeepening of a drawer to allowa shallow sliding tray to befitted therein.Back and Front

Finally, there is the backand the front. To save weight,they are usually framed up outof 1 in. x 11 in. stuff with aplywood panel. The backcan ',be screwed or buttoned

Drawer bottoms

Constructional details of the drawersand handles

into place from the inside, when the drawersand stops have been fitted : it being neces-sary to remove the drawers in order to insertthe screws. The front is fitted with pinehinges working in grooves in the sides or,better still, in brass guides let into the sides.I f desired, a solid back and front may befitted, when the thickness can be somewhatreduced. The edges must be clamped ormitre -clamped, and the inner surface of thefront worked down with a router, or rebate -plane, or its edges may be merely lipped totake the baize covering, remembering thatit is necessary to plough shallow groovesabout 1 in. or so in from the edges that arenot clamped, before commencing to cleanout the sinking. There are times, however,when a detachable front is of considerableuse as a safe surface for precision tools orslip-gauges-especially if one is workingaway from the bench at a large surface -table or on a machine. This end can beachieved by fitting small flush -bolts asshown in the sketch instead of pin hinges.When shot, the bolts act as hinges, andwhen withdrawn, the front can be liftedout without any hindrance, thus making itsliding, or detachable, at will.

thickness of the drawer front, j in. for thethickness of the drawer back, another in.as clearance between the drawer and theback of the cabinet, which latter willaccount for another in. to in., making aminimum total of 8%s in. for the overalldepth of the cabinet, excluding the thick-ness of the front and the allowance for thedrawer handles, which brings the grandtotal to something in the neighbourhood of9 in. or 10 in. Flush handles, as shown inthe sketch, should now be fitted.

pacesaving forshallow drawers

Depth of DrawersBefore concluding, the depth of the

drawers from back to front deserves somenotice. Interiorally, it should not be lessthan 61 in., preferably an inch or even twomore, otherwise squares, large calipers anddividers may have to go in askew, orlengthways, and thus waste some valuablespace. To this must be added sin. for the

Back and front joints

Details of the slidingfront of the cabinet

Mitre tenonedand panelled

Drawer details

The Sun's EnergyCNGLISH and American scientists have at

last completed their experiments regard-ing the mystery of the sun's apparentlyinexhaustible store of energy, without whichlife on earth could not exist. A " cosmicphoenix "-carbon for ever being devouredin flames of hydrogen and yet resurrectingitself in its full original state to start thecycle all over again-has been proved tohave existence within the sun, and the starsas well.

So great is the amount of atomic energycontained in the sun's hydrogen, that it isheld that it will keep the sun radiating foranother 12,000,000,000 years.

A Plastic AeroplaneAFTER Colonel Stromme, of the United

States Army Air Corps had witnessedtests of a new plastic plane which had beenpoured, pressed and baked, he said: " Wesee demonstrated the possibility that aero-planes soon may be turned out of mouldsswiftly and at comparatively low cost. Thismay start a new era in mass production ofmilitary and commercial aircraft."

The Timm Aircraft Corporation, at VanNuys, California, have produced the plasticplane which is made of a new material whichis 20 per cent. lighter than present planematerials. It is made by saturating andbinding thin strips of spruce with liquidplastics. Bolts and rivets are dispensed withas the fuselage parts are simply pressedtogether.

It is claimed that the plane has higher fuelcapacity, can carry heavier loads and has abetter performance than other types ofplane.

A Sensitive DetectorADETECTOR, so sensitive that it can

find approaching aircraft at distancesmore than fifty miles away and so givedefending forces about a quarter of an hourto get ready for them, has been perfected bythe United States Army. The device isbeing kept a secret, but it is understood touse light waves and to be capable of pene-trating any degree of darkness or fog. Thedetectors will cost about £13,750 each.


MODEL AERO TOPICS

Win4 Fix in (0'

If you have Been Pondering over how to attach theWings or Tail to your Model you will find a Solutionto your Problem in the Methods Described Here

STRUT

HARD SHEETBALSA

ONE of the most important details ofmodel design concerns the wingfixing. In the tuning up stages it

is particularly necessary that the wingshould be easily adjustable yet reasonablyrigidly fixed. It must, moreover, be able totake a wing tip landing without damage.Particularly, is this necessary with a petrolmodel, and so aero-modellers have beenespecially ingenious in devising various wingfixing methods which combine these import-ant desiderata.

It has not taken long for us to developthe modern contest model to a fairly highdegree of streamlined perfection. We areusing circular or elliptical section fuselagesof good outline, with spinners and foldirgairscrews, low -resistance undercarts, or

PARS C. 'WING ANFUSELAGE

SOCKETS

Fig. 4.-A permanent style of wing fixing

even retractable gears, and well -shapedwings and tail surfaces.

The only parts left to improve, it seems,are our structures for holding the variouscomponents together. The wing for instancepresents rather a problem, when it has to besufficiently flexible to " give " in a crashand yet to be fixed in such a way as topreserve the streamlining.The Parasol Wing

Of the streamlined class, the parasol wingmodel seems to be the most popular, andso we will take this type first. Fig. 1 showsa mounting which has been used on aWakefield model, and which, it is believed,causes less interference between the wingand the fuselage than any other type.

There are no external fittings, the wingrubbers being enclosed in the mounting

(Chi) Fixturessuitable for Wake-field models.(Left) The Frenchmethod of fixing.(Below) Press

fastener style offixing

WING

Methods

HOLLOWMOUNTING

SHEET BALSAO

pliffillikeikeitumgar//-

'

Mikiitself, yet it allows full flexibility and thewing position is adjustable. The actualseating is made from two balsa blocks,shaped, hollowed out, and glued together.Rubber hooks are attached to the wingspars, and to a hard balsa beam inside thefuselage.

French modellers seem to favour a centralfixing, and struts on parasol models. Sucha fixing is shown in Fig. 2. It has theadvantage of easy construction, and if themodel has conventional V -dihedral, thismay be adjusted by use of several struthooks on the fuselage in different positions.Reed -Cane Struts

Unless reed -cane struts are used, whichbend easily under shock, it is suggested that" snap out " connections be used, as shownin Fig. 3. The wing strut hook is madefrom the " spring " half of a clothing snap(press stud), and is firmly glued and boundto the under surface of the wing. The wireend of the strut, which should be of about22 s.w.g. is then bent over, so as to form asnap fixing with thepress stud.

The fit should bejust tight enough, only'to come apart whensubjected to a sharpknock on the under-side of the wing.Should the model onlanding " turn turtle "the wings will be ex-posed to a downwardthrust, and the fuse-lage strut hooks willthen disengage.

Fig. 5. - Anotherstyle of wing fixing

Some of the best streamlined modelsproduced in this country have been shoulderwing monoplanes, and whilst the construc-tion difficulties surrounding this type are,perhaps, greater than most, the finishedproduct is usually worth the extra workinvolved.A Disadvantage

Theoretically, the only aerodynamicdisadvantage is that considerable filletingaround the wing roof is necessary to ensurea good smooth passage of air around thatpoint. The comparatively low position ofthe wing should be an advantage, since itplaces the centre of drag more directly inopposition to the thrust line.

The constructional disadvantages are, ofcourse, that it is difficult to make the wingadjustable and flexible yet preserve thestreamlining at the same time.

The best way of getting over this prob-lem is definitely to fix the wing positionand angle of incidence whilst the model isin the design stage, and should it be neces-sary to adjust the centre of gravity whenconstruction is completed, do this by meansof a trimming weight.

A fixing along these lines is shown inFig. 4. The fairings may be cut from softbalsa and hollowed out, being fixed toeither the wing root or fuselage. Theshort connecting spars are 'also of balsa, sothat on a heavy impact they would snap,leaving the wing unharmed.Low Wing Models

Low wing models have, never been sopopular as high wing, and since the increased

ALUMINIUM LINED SLOTS

BALSA BOX

THIS ANGLE EQUALTO DIHEDRAL ANGLE ---

SHEET BALSA

DURAL TUBE

BAMBOO- -CONNECTORS in


weight rules for Wakefield models, thistype seems to have been even moreneglected.

Possibly this is because considerabledifficulty is experienced in mounting thewing on a circular or elliptical sectionfuselage. In Fig. 5 is shown the method ofattaching wings which, besides being shockabsorbing (each wing -tip will flex 2 in. inan upward direction and can be knockedright out in a head-on collision), the fairingsprovide good streamlining, and the angleof incidence may be adjusted.

The secret is to keep the bamboo con- ,

necting spars 'as thin as possible, for aswell as providing good flexibility these willthen break first under heavy stress, andthus prevent more extensive damage.

The fuselage slot will allow two or threedegrees of adjustment for wing angle ofincidence, without becoming exposed. Ifnecessary a short rubber band may bepassed across the bottom of the fuselage,and secured with small hooks to the wingroots.

Tail SurfacesNow we come to the tail surfaces. Some

designers prefer to use a detachable tailboom, with the rubber built integrally.This is shown in Fig. 6. The stabliser ismounted on the rudder by a central doweland tube fixing, and is adjustable by meansof a very small nut and bolt at the leadingedge.

The whole assembly is easily knocked offin the event of a collision, but during thetake -off this is prevented by the tension ofthe rubber motor.

For those who prefer twin rudders,

especially if no tail boom is used, theassembly shown in Fig. 7 will be very good.The fairing blocks are built on to the endof the fuselage, and are hollowed out for

SLOTS TO RECEIVE KEY'

UBBER

0)1)HOLLOA W

BALS

ment, and thus acting against each other.Connecting the Elevators

To connect the elevators, the wire "key"with the rubber attached is drawn throughthe tail block and passed in a horizontalposition through the hole in the root tib ofthe elevator. It is then turned to a verticalposition and the tension of the rubberallowed to pull it into the slots and draw

SLOT FOR STABILIZERADJUSTMENT

lightness, and to allow the rubber bands topass through.

The bamboo plugs, which are firmlyfixed into the tail block, should be shortenough to allow the elevators to beknocked off in any direction, since thetension of the rubber bands holds themrigid during flight.

Twin rudders are best built on tothe stabiliser, since this will obviate allchance of them becoming out of adjust -

Figs. 6 and 7.-(Right).4 detachable tail boom.(Left) Fixing for twin

rudders

the bamboo plugs into, their sockets.Although this type of tail attachment

does not permit adjustment, it is veryflexible and lends itself to fine streamlining.

NEW INVENTIONSAutomatic Fire Alarm

AANEW automatic fire alarm signalshould act as a faithful sentinel in

hotels and factories. It would prove usefulalso in the homes of the people, especiallyas it is not very costly. The modus operandiof this warning device is literally striking.At a temperature of 160 degrees, fusiblematerial is melted; a pin strikes a percussioncap on a blank cartridge, and this explodesin a combustion chamber. There is a reportlike the firing of a pistol, which' naturallycalls immediate attention to the con-flagration.

Portable Hat Rack for LadiesAN American lady has contrived and

patented a hat box for travellingpurposes. It contains a rack with holders,one above the other, for about half a dozenhats. When the box is being carried, thehandle directly supports the rack. In shapethe box resembles a vertical cylinder.I imagine it is designed to accommodate thefair owner's repertoire of holiday headgear.

Helmet With Mobile CrownTHE steel helmet continues to variate.

Its latest -development has appeared inthe United States, where a patent has beengranted for what is styled an armouredhelmet. This is a two-piece head coveringcomprising a brim and a separate crown.Resilient means connect the brim andcrown and normally join them. But theconnecting means can be extended, per-mitting the crown freely to move on the

brim, in the event of anything striking it.It is evident that the steel helmet worn byour soldiers, police, air-raid wardens andothers is definitely rigid. In the case ofbeing struck by a missile, it does not givebut obstinately resists the impact. On thecontrary, the resilience of the new armouredhelmet qualifies it to modify, like a bumperor spring buffer, the intensity of any violentcontact.

Patent BricksTHE war has put the skid on the wheel

of building operations except in thosecases where they concern the militarysituation. Still, I nate that more than onecurrent application to the British PatentOffice relates to building materials.

Suitable for air-raid shelters, an inven-tion of this kind comprises a number ofcast or moulded hollow bricks. These bricks-which can be filled with sand or gravel-have alternating projections and recessesenabling them to fit together, so that nobonding is required.

The inventor of another device has sethimself the task of producing a syntheticmaterial for building purposes, which willresist moisture and the deleterious effectsof changing atmospheric conditions.

This synthetic material may be used inthe making of what are commonly termedartificial stone blocks, jointless floors,partition walls and other structures normallymade from concrete, tiles or plaster. Theprocess includes a synthetic resin which iscapable of being hardened. And, to lendenchantment to the view, the materialmay be coloured by the use of aniline dyesor pigments.

BOOKS RECEIVED

" Capstan and Turret Lathes." By E. T.Westbury. Published by Percival Mar-shall & Co., Ltd. 112 pages. Price 2s. net.

'HE object of this handbook is to' describe in a practical way the- design

and uses of capstan and turret lathes asemployed in modern engineering works. Thesubject is treated in a manner calculated tobe of direct assistance to the lathe operator,tool -setter, apprentice, or engineeringstudent.

" Pattern Making." By T. Spedding. Pub-lished by Percival Marshall & Co., Ltd.84 pages. Price Is. 6d. net.THIS book is intended as an introduction

to the skilled craft of pattern making,and contains Much useful information forthe engineering student and draughtsman.The book, which is well illustrated, shouldalso prove of service in the small generalengineering shop- and the home workshop.

" Man of Power." By Ivor B. N. Evans.Published by The Scientific Book Club.288 pages. Price 2s. 6d. to members.

THISbook contains the life story of the

great scientist, Lord Rutherford, O.M.Little is known of his work outside hisstartling discoveries concerning the atom,and the book tells the story of his remark-able achievements, and their value tohumanity. The book also reveals thehuman side of Rutherford, and shows himas a man of simple tastes. It describes hislife as a boy, as a student at Cambridge,and as a professor in Montreal, Manchester,London, and, finally, Cambridge again. Theauthor is himself a scientist and was one ofLord Rutherford's greatest admirers.


-A Telephone ClockThis clock has been Designedby the Bell Laboratories and isIntended to Symbolise the Im-portance and Time Measure-ment in the Engineering andOperation of Telephone Plant

Fig. 1.-The " Telephone Clock" and its eight companion clocks

THE new " Telephone Clock " in oneof the 'Broadway windows of theAmerican Telephone and Telegraph

Company headquarters building has arousedconsiderable interest by its accuracy andstriking appearance. Designed by the BellLaboratories, it is intendedthe importance and time measurement inthe engineering and operation of thetelephone plant.

The accuracy of the clock is emphasisedby a large dial on which the sweep -secondhand moves in a graduated circle nearly3 ft. in diameter. Hour and minute handsmove in smaller circles at the centre inorder to allow an unobstructed view of theprecision dial. Mechanisms for driving theclock from current accurately controlled bythe Bell System Frequency Standard, andfor synchronising the motion of the handswith signals from the New York TelephoneCompany's Time Bureau, are mountedcompactly in a hemispherical case behindthe inner dial. The principle of operationis illustrated in the schematic diagram,Fig. 5 ; only the basic elements are repre-sented, the alarms, power facilities, andsome details of the control system beingomitted for clarity.The " Real " Clock

Control of rate originates at the Labora-tories, where the primary frequency standardis maintained. Here, in the clockmaker'ssense, is the real clock-the element whichtakes the place of the pendulum in the usualprecision clock being a vibrating crystal ofquartz, so carefully construct -Rd and soprecisely controlled that, when used tomeasure time directly, it is accurate to lessthan one -hundredth of a second a day.Precise submaster oscillators, supply sixty -cycle constant -frequency current to theclock and to the New York TelephoneCompany's Time Bureau. The current isso regulated that synchronous clocksoperated continuously from it will deviateless than one -twentieth of a second fromNaval Observatory time. The performanceis checked frequently and precisely at the

Time Bureau by comparison with radiotime signals received via Arlington. Thesixty -cycle supply is carried over two separ-ate cable pairs following different routes.As long as either circuit is complete theclock will continue to function normally. sothat a high degree of reliability is assured.Even if both of these circuits should fail,the clock will continue in operation, becausean automatic switch not shown in thediagram will substitute an input from thecommercial A.C. power supply, which inNew York City is normally adjusted fromthe same constant -frequency source thatsupplies the Time Bureau and the clock.Two Motors

The clock contains two motors. One ofthese, having two similar windings, is usedfor the regular drive and is constructed sothat sixty -cycle current from both or eithersupply circuit operates the hands at thenormal rate. The other motor also has twowindings, so arranged that they will produce

forward or reverse rotations respectively;it is geared to the clock mechanism in sucha way that while in operation it producesa change in rate of about one per cent. Thetwo motors are geared to the clock througha differential, the reversible one being usedfor preliminary manual setting and forprecise automatic synchronisation.

Synchronisation of the clock with signalsfrom the Time Bureau is accomplishedthrough the use of contacts operated froma -cam mounted rigidly on the same shaftwith the second hand. Four times eachminute four sapphire pallets drop in closesuccession from raised portions on this cam.The operation of the first pallet opens acircuit normally closed, and the operationof the second pallet closes a circuit normallyopen. During a brief interval both of thecircuits are open. A short pulse, generatedat the beginning of each signal from the

Fig. 2.-Partial assembly of the clock without dial.photographed from the back

Time Bureau, is normally received in theinterval between the functioning of thesetwo contacts. But if it should arrive beforethe first contact has opened, or after thesecond one has closed, it is directed to arelay which starts the reversible motor inthe appropriate direction to restore normaloperation. Thus at all times the secondhand should indicate the same time as thatdistributed by the Time Bureau; thedepartures from synchronism are expectednot to exceed one -hundredth or two -hundredths of a second.Trouble Tracking

Provision is made to call attention toincipient trouble which might in time affect

Fig. 3.-A rear view of the clock showing the cam and the operation of the clock. One indicatorsapphire pallets and the two mirrors --shows whether the power is removed from


Fig. 4.-A close-up view of the clock shown in Fig. I

any part of the system. Another callsattention to the omission of synchronisingpulses from the Time Bureau in case ofcircuit failure or any other irregularity.Others operate if the synchronising deviceis called upon to function more often thanis normal, if any part of the standby equip-ment is called into action, if the voltage ofconstant -frequency supply falls below nor-mal or if, for any reason whatsoever, theclock should stop.

To ensure continuity of operation, thestandby equipment is arranged so thatadjustments may be made on any part ofthe system, exclusive of the clock itself,without affecting the accuracy of theindicated time. Valves can be changed inthe amplifiers, the regular power source mayfail, or either control circuit may be inter-rupted, with no more effect than to lighta lamp which localises the irregularity andto ring an alarm bell calling attention to it.

The Glass DialThe mounting of the

seventy -pound glass dialwas accomplished in aninteresting way. A metalring was made having adiameter somewhat lessthan that of the inner dialcircle, and to it wereattached twelve thin -walled steel tubes at posi-tions correspondingexactly to the five-minutemarkers. These tubeswere machined to fitsnugly into small holesdrilled through the glassbehind the markers. Asthey are somewhatflexible, the weight of theglass is distributed moreor less equally amongthem. The dial is heldfast to the metal ring by

steel screws which go throughthe tubes and into the metalfive-minute markers. Thering, in turn, is fastened tothe main supporting castingby a separate set of screwsinserted from the rear.

The dial is illuminated bya set of twelve small lampssupported in holes drilledthrough the glass behind themetal discs bearing the hournumerals. By the use ofspecial mirrors, not visiblefrom the front, nearly all ofthe light is directed laterallyinto the glass so that it d'oesnot appear until it strikessurfaces which reflect it inother directions. Thus theengraved graduations andnumerals at the outer edge

of the glass stand out effectively asthough made of self -luminous material.Most of the light not used in illuminatingthe dial from within escapes from the edgeand makes an effective luminous border.The effect of this lighting method is enhancedby the use of crystal-clear optical glasshaving only a small fraction of the absorp-tion of ordinary plate. Although the chiefscientific interest centres on the largeclock because of its unique accuracy, con-siderable attention has been drawn toeight smaller clocks adjusted to indicatethe time in various places throughoutthe world.

These eight clocks are structurally allalike, and all operate from the previ-ously mentioned Commercial power supply.They differ only in the setting whichpermits them to indicate the hour, theday of the week, and if it is morning orafternoon in any selected locality.

Reproduced from the Bell LaboratoriesRecord.

SOURCE A

SOURCE B

ygigI-NG g7 /MOTOR

S

LONG LINESDEPARTMENT32 SIXTH AVE.

TIMEPULSE

REVERSIBLEMOTOR

SLOW (RELEASE

SLOWRELEASE`_

OOQr-

III

AUXILIARY CONSTANT -FREQUENCY SUPPLY

CHECK

aLL

4

BELLTELEPHONE

LABORATORIES

NEW YORKTELEPHONECOMPANY

TIMEBUREAU

Fig. 5.-A simphfied diagramof the clock

Textile Mill EquipmentA Device for Variable Speed Control and a New Sh uttleless

Loom of the Automatic TypeAYORKSHIRE engineering firm hasmarketed a new device for variable

speed control. It has a simple lever controland an infinitely variable speed ratio of74 to 1. The variable speed pulleys operatewith standard V ropes and the variation inspeed ratio is made by the movement ofa lever through an arc. By this means theV ropes running in two sets of interlockingvariable speed pulleys are pulled tighter andslackened off respectively, the pulleys auto-matically adjusting themselves to thechanged" position of the V ropes.New Type of Loom

A new model of the shuttleless loom is anautomatic type for the weaving of woollenand worsted fabrics. It has the remarkableproperty of being able to run with any oneof a battery of seven different colours orqualities of weft yarn wound on cones.Below these are seven other cones and theends of the upper row are tied to the be-

ginnings of the lower., When a cone runsout the lower one is moved up to the placevacated and a new cone placed below andtied up as before. Each of the seven weftends is threaded through a tensioningguide bar and is maintained in positionready for the indication by the patternchain that that particular colour is re-quired.The Gripper

The weft is fed half -way across the shedby a light metal arm with a gripper end.This gripper releases the yarn to the grip ofanother arm operating from the oppositeside of the warp and then returns to theoperating position again ready for its nextpick. The weft is drawn the remainingdistance by the receiving arm, after whichthe pick is beaten up in the ordinary wayThe selection of colours is by means ofa separate pattern chain incorporated in thedobby.

BOOKS RECEIVED" 1,001 Mechanical Facts Made Easy."

Edited, by Percival Marshall, C.I.M.E.Published- by Percival Marshall & Co.,Ltd. 108 pages. Price 3s. 6d. net.THIS handy pocket volume, which is

primarily intended for the non -technicalreader, contains over 500 paragraphs andnumerous illustrations explaining in a veryclear manner the basic principles ofmechanics and engineering processes. Thebook is well illustrated with line drawingsand half tones." How to Work Sheet Metal." By H. J.

Dyer. Published by Percival Marshalland Co., Ltd. 142 pages. Price 2s. 6d. net.

THE worker in sheet metal will find muchuseful information on the tools used and

processes employed in general sheet metalwork, within the covers of this smallvolume. The book is divided into 15chapters, covering amongst other subjects,Metal Used ; Hollowing and Blocking ;Edging and Seaming ; Beading and SwagingMachines ; Riveting; Soldering and TankConstruction. Numerous clear-cut illustra-tions are a feature of the book.


SCALE MODELAIRCRAFT No. 4.

of such labour-saving devices asautomatic riveters and, wherestrength considerations permit,electric welding machines.The Simple Main Plane

As may have been gathered fromthe preceding figures, the greateststructural improvement has beeneffected with the main plane. Thisis of simple form in plan althoughits front elevation is slightly com-plicated by a thickening of thesection towards the root. The wing,which is built in two halves, boltingdirectly to the fuselage, is of asingle -spar type. The spar, whichis a simple I -section unit (in strongcontrast to the complicated built-upbox of the earlier D510) forms thebase of the wing to which main andleading -edge sections are attached.The web of this simple spar is_ aheavy -gauge light -metal blank, towhich, on each side, heavy top andbottom flange sections are riveted.The plain surface of the web

The Dewoitine D520By J. H. Stevens, A.R.Ae.S.

A Single -Seater Fighter which is the Fastest Machine of thisType in Service with the French Air Force

riE11115 is the fastest fighter in service-with the Armee de l' Air, at the time ofwriting, and the information that it

had come into service was only releas3d. inApril of this year. It is a more recentmachine than the familiar and successfulMorane 406-C1, as it was designed to areplacement specification for that type andis, naturally, considerably faster. It mightbe as well to clear up one point about theDewoitine. Although it bears the name of adesigner whose firm has long been famousfor its single -seater fighters, the D520 is theproduct of the Socidg Nationale A Construc-tions Aironautiques du Midi This apparentanomaly arises from the fact that the oldDewoitine company was " nationalised " in1936 under the compukory legislation of thelate (unlamented) " Popular Front " govern-ment, by which the firms of the militaryindustries were organised into groups forareas, i.e. Midi, Ouest, Nord, etc.

DevelopmentThe D520 may be considered as the

logical development of the D500 and D510,which have been in use in France for severalyears, as well as being on active service withthe Republican Air Force in the SpanishCivil War. The prototype D520 was firstflown in the autumn of 1938 and, althoughit was not actually shown, details were firstreleased at the Paris Salon in December ofthat year. Early in 1939 several develop-ment versions appeared and they wererigorously tested with a view to eliminatingall the bugs " before the arrival of theproduction type in service. In the summerof last year a special version, known as theD530, was being cleaned up and fitted withan extra high-powered engine for an attemptto break the speed record of 469 m.p.h. set

up by the Messersehmitt Me. 113R, inApril of that year.

Ease of ProductionThe chief feature of the D520 is that it

has been specially designed for rapid large-scale production. Although it is a far moreadvanced machine than its predecessor (theD510), being more carefully streamlinedand faired, with extra equipment and thecomplication of retractable landing gear,the manufacturing time has been halved.The makers claim that the working time is7,000 man-hours per machine. Two exam-ples of where time has been saved are in themaking of the main spar and main -planeribs, which now take 324 hours and 60hours respectively, against 1,993 hours and1,360 hours for the older machine. Thisimprovement in production time arisespartly from the use of refined and modern-ised manufacturing technique and partlyfrom improved and simplified structuraldesign. The maximum use has been made

PRINCIPAL CHARACTERISTICSDewoitine D520

900 h.p. Hispano Suiza 12 Y -errs*Span .. .. 33 ft. 5 in.Length .. 27 ft. 01 in.Wing area 150 sq. ft.Weight loaded .. 4,850 lb.Wing loading .. 32.33 lb. sq. ft.Max. speed (13,120 ft. 329 m.p.h.Landing speed .. 70 m.p.h.Climb to 13,120 ft. 3 min. 58 sec.Service ceiling .. 34.440 ft.* These figures are those released for the proto-type at the Paris Show in December, 1938. Itcan be taken that they have been comiderablYimproved for the production machine.

is stabilised at intervals by rivetedangle -section shear members. The spar issituated about 30 per -cent, of the chordfrom the leading edge, so that it lies approxi-mately at the centre of pressure of the wing.The part of the wing ahead of the spar isfairly large and is built up as a unit, with astress -bearing skin riveted- to flanged -blankribs. Once this section has been attachedto the spar, it forms a strong " torsion box "and is the main strength of the wing.Similar flanged and lightened sheet -metalribs are attached to the rear face of the sparand connect it to the light rear spar-thelatter being little more than an anchoragefor the flaps and ailerons. The whole ofthe wing is covered with a stress -bearinglight -alloy skin.

Contrary to usual practice in fighters, theflaps, which extend from the inner ends ofthe ailerons to the fuselage fillets, are of theslotted type. The ailerons are fabric -covered structures and are mass balanced.

The Semi-Monocogue FuselageThe fuselage is an oval -section semi-

monocoque structure, with good lines,somewhat reminiscent of the Spitfire, butcharacterised by the rearward position ofthe cockpit and the rather less refined noseshape occasioned by the bulk of the HispanoSuiza engine. The nose, it will be noticed, issomewhat pigeon -chested and the spinnerdoes not have the " fairline " usual withmodern British liquid -cooled installations,but the lines of the rest of the fuselageeasily make up for any deficiencies in thenose. The clean sweep of the cabin fairinginto the long, thick fin is particularly fine.The pilot's cockpit has the usual trans-parent covering, with a Trout panel ofarmoured glass.

452 'NEWNES PRACTICAL MECHANICS July, 1940

The original engine of the D520 was the12 -cylinder vee, liquid -cooled HispanoSuiza 12 Y-crs, moteur canon, of only900 h.p. The first of the developmentmachines, which appeared in February,1939, was fitted with the 1,100 h.p. 12Y-51engine, which gave it a maximum speed of340 m.p.h. A three -bladed controllable -pitch airscrew is fitted as standard. Theradiator is mounted in a ducted cowli igbeneath the fuselage. The main fuel tankis carried in the fuselage and is one of theseveral French " fireproof " designs; pro-vision is also made for jettisoning the petrolin cases of emergency.

The " Moteur Canon "A word about the famous Hispano Suiza

engine -mounted gun may be of interest.This first made its appearance about tenyears ago, although numerous experimentswith operating small -bore guns from aero-planes had been made in the last war. Thegun id question is enabled to fire forwardwithout an interrupter gear, because it ismounted between the two banks of cylindersand the shells pass through the hollow shaftof the spur gear and the airscrew. The gunweighs 106 lb., and the magazine of 60shells another 55 lb. The muzzle velocity ofthe projectiles is 2,890 f.p.s., and the rate offire about 450 rounds per minute.

The undercarriage of the D59.0 consists oftwo single -leg units which retract inwardly.the wheels lying in the juncture of the lead-ing edge of the main planes and the fuselage.The openings for the legs and half of thosefor the wheels are covered by fairing platesattached to the legs themselves.

The tail unit consists of an all -metal finbuilt integrally with the fuselage, a canti-lever stressed -skin tail plane, and fabric -covered, metal -framed, control surfaces.Both rudder and elevators are fitted withtrimming tabs, mass balances, and aero-d ynamie balance portions. Details ofarmament have not been released beyondthe fact that the prototype had two machine-guns in the wing besides the shell gun.Identification

The aeroplanes of France have always beendistinct from our own in not bearing cock -

SIDE, PLAN AND FRONT VIEW OFDEWOITINE D520

ades upon the fuselage sides until this year.Presumably increased problemof identification with the high speeds andsimilarity of modern designs, cockades arenow painted on the sides of the fuselages ofthe aeroplanes of the Arm& de l'Air.

French cathouflage is lighter than ours,consisting of smaller irregular patches ofkhaki and grass green. The under surfacesare a light French grey. The national mark -

THE

ings are cockades on the wings and fuselageand stripes on the rudder; the ringsblue, white, and red from the inside to theoutside, and the rudder is blue, white, andred reading towards the rear. A whitenumber is painted under the wing and asquadron crest is usually carried on thesides of the fuselage. Mere precise details ofcolouring cannot, naturally enough, bedivulged in wartime.

Robert I.

MUSICK MEMORIAL TROPHY AWARDSAward for the Outstanding Contribution to Trans -oceanic Air Transport

Minshall who has been awarded theMusick Memorial Trophy.

ROBERT J. MINSHALL, vice-president in charge of engineering ofthe Boering Aircraft Company,

Seattle, has been awarded the MusickMemorial Trophy for 1940, an internationalaward given for the most valuable contri-

butions to flight safety, particularly in thefield of trans -oceanic flying.

The award was based on his " out-standing contribution to safety of trans-oceanic air transport through major engin-eering improvements in large flying boats."Minsball directed the engineering of the74 -passenger, 41 -ton Boeing 314 Clipperswhich were introduced a year ago andplaced in service on the transatlantic andtranspacific routes of Pan American Air-ways.

First AmericanNotification of the final selection for 1940

was received recently by Major Lester D.Gardner, executive vice-president of theInstitute of Aeronautical Sciences, NewYork, in a cablegram from the award head-quarters in Auckland, New Zealand. Min -alien is the first American to receive thetrophy. It was awarded last year to ArthurGouge of England, general manager andchief designer of Short Brothers, Ltd., asdesigner of the Sbort Brothers EmpireFlying Boat.

Minshall, an engineering graduate of the

University of Washington, Seattle, joinedthe Boeing Aircraft Company in 1918. Hebecame design engineer in 1928, chiefengineer in 1936, and vice-president in 1938.

Captain Edwin MusickThe Musick Trophy, in memory of

Captain Edwin Musick and his six com-panions who lost their lives in 1938 whilepioneering a new air route from the UnitedStates to New Zealand, was established inthat year by the citizens of New Zealand.The recipient of the award is selected by acommittee representing New Zealand, theRoyal Aerohautical Society of GreatBritain, and the Institute of AeronauticalSciences fig the United States. The trophyis awarded annually to the individual inthe United States or Great Britain who,in the committee's opinion, " makes themost valuable contribution toward thesafety of life in the air, with especial regardto trans -oceanic flying."

NEXT MONTH :A special article on the formidable

fighters of the R.A.F.

July. 1940 NEWNES PRACTICAL MECHANICS 453

SCALES FOR ITIETRE ItiMETRES 211ETRE rIOCitLI

r '14z,

IZ 117,1'c6,

Fig. I.-A longitudinal section showing the engine, etc.

A Boiler for the Model Cargo BoatBy E. W. Twining

Previous Articles on the Construction of the Model Cargo Boat appeared in the March and May issues

THE hull of the ship having beendesigned, its size or sizes and dis-placement all determined by Mr.

Clifton, and his drawings reproduced inthe pages of the last issue of " PracticalMechanics," it remains forme to fulfil my promise,made in the first article, toprepare designs for thesteam generator and itsaccessories. The reader willappreciate the fact that thedimensions of a boiler ofthe utmost size and steam -making capacity could notvery well be arrived atbefore it was known whatspace would be availablefor it within the hull, hencethe reason for the enginebeing given first, then theship which the engine shalldrive and lastly the boiler.

Size of Model to BuildWhen I prepared the

drawing for the four -cylinderengine I was inclined toadvocate the larger size,viz. : the 1 in. bore andstroke, but since I haveseen Mr. Clifton's drawingsfor the vessel I am more infavour of the one -and -a -half metre model hull, theengine for which will havecylinders in. by in. Indesigning the boiler there-fore, I have worked withthis in view and althoughI have appended scales tothe drawings for both largerand smaller units the pro-portions of the plant

throughout, including the Bassett-Lowkefittings, are those most suitable and bestfor the intermediate size, that is to say for

the I by I engine and the five feet (nearly)hull. The reader will understand from this

SCALES FOR IMRE, P*I1ETRE & MIRE MODELS

Per2"'1.1.1.1.1

2,

f' , A",

ila#4120 - rAWVFig. 2.-A cross section through the boiler

that in the event of his deciding upon eitherthe smaller or the larger ship model somedetails in the boiler and in the water andspirit tanks may need slight modification,chiefly in the matter of thicknesses of plate.

tubes and materials andsizes of some of the fittings.

37 Amongst the last, whichwill be affected if anotherscale is adopted, will be thehand pump in the watertank and the spirit -controlneedle -valve in the fueltank. The chief troublewith a metre -length hullwill be to obtain thesesufficiently small. With asmaller boiler too the watergauge may present adifficulty and simplegauge with bent glass tubemay have to be used.

DORT Should anyone make uphis mind to construct a two

/ metre model, that is to sayone having a length on

L waterline of 6 ft. 6 ins..I recommend him to con-sider the question of thebest method of fuelling/ very carefully, before adop-ting methylated spirit. Sucha big ship calls for some-thing more economical andI think that paraffin vapor-ising burners fed teem apressure oil tank would bethe best scheme. On thispoint, with a teW tofinding out what burnersand tanks are available,Messrs. Bassett - Lowke'scatalogue may well beconsulted. "Primus"


burners would be ideal for the job, but Iam not sure whether these are obtainableat the present time.

Removable DecksIn his article Mr. Clifton provided for the

upper deck being removable to gain accessto the machinery. This is, of course, as it

Fig. 3.-The fuel tank.

FUELTANK

should be, but now that the WI arrar g?,mentof the boiler and tanks has been set out Ifind that the tanks extend, both fore andaft, beyond the limits of this deck andconsequently portions of the fore and afterwell -decks will have to be made detachable.Moreover these movable decks should bemade of metal ; that immediately over theboiler, at any rate, if not the whole of themfor, although the upper deck is protectedon its underside with a sheet of Asbestos,a wooden deck would not stand up to theheat which is bound to be radiated from theboiler casing without in time becomingdistorted.

The removable decks are provided, andare fortunately only necessary, for thepurpose of getting the several portions ofthe power plant into and out of the hull.The parts which call for frequent access,i.e., the steam regulator valve to the engine,the boiler water filling plug, the spiritneedle -valve and the hand -pump leverhave all been arranged to come undereither cargo hatches or, in one case, theengine room skylight. This merely involveshinging these details so that they will openas small flaps.The Boiler

This is of the semi-watertube type andconsists of two large steam collectingdrums, two smaller water drums, anarrangement of down -flow tubes and aseries of steam generating water -tubes.The disposition of all of these is mostclearly shown in Fig. 2 which is a crosssection through the hull of the vessel andthrough the boiler on a plane taken throughthe centre -line of the funnel.

Fig. 1 also is a section, in this case takenlongitudinally on the centre line of the shipand cutting through not only the watertubes but two curved pipes which arch overand connect the, two steam drums togetherat the top. From the after one of these thesteam pipe is led to the engine and upon thetop of it the safety valve is mounted. Uponthe other pipe the screwed collar of afilling plug is brazed. This plug comesunder the small cargo hatch on the upperdeck.

The whole boiler should be built up ofseamless copper tubing with ends to thesteam drums of either flanged copper discsof No. 16 gauge or gunmetal castings asshown in Fig. 1. Whichever is used the endswill need staying with 3/16 in. hard drawnbrass rods. The extended ends of thesestays form the means of supporting theboiler in the casing at the after end. Atthe forward end both the steam drums aremade to project a quarter of an inch beyondthe casing through holes cut to receivethem. Support is thus provided at this endalso. It is at this, the forward, end of theboiler that the gauges and the check valveare fitted ; the water gauge in the starboarddrum and the check -valve and pressuregauge in the port drum.

The boiler may be soft soldered togetherif desired but it must be pointed out thatshould the model become stranded in weedor shallow water beyond reach for a con-siderable length of time and the boiler rundry much damage may be sustained. Itwill therefore be far safer and make thestronger job if all joints in the'boiler properare silver -soldered.

It will be noted from Fig. 1 that the steampipe is led, from a point near the safetyvalve, forward and downwards before beingreturned aft to the wheel valve and theengine. It thus provides a simple means ofsuperheating the steam.

A Pressure Gauge reading to 100 lbs.should be fitted and the working pressuremay be anything the reader chooses up toabout 75 lbs. It is very likely that 40 lbs.per square inch will be ample to drive theboat at sufficiently realistic speed.

The Boiler CasingThis is made up from soft iron or steel

plate of about No. 22 S.W.G. ; one end maybe riveted in and the other - since one endmust be removable-screwed by tappingholes in the flange. The conical smoke -boxmust also be held down on the casing byscrews. From the upper end of this cone aninner funnel extends nearly to the top of theouter, painted, funnel. This inner funnelcan be made from a piece of thin brasstubing. It must be given arake, aft, equal to the angleof the outer funnel. Thereis, of course, no connectionbetween the two, so thatwhen the upper deck islifted the outer funnel willcome away with it leavingthe inner funnel standing upfrom the boiler casing.

The Spirit Burners and TankThe furnace is provided

by eight burners of Asbestoswick fitting into shortlengths of brass tubing allconnected together by crosstubes, see Fig. 1, and to thetank by a copper pipe, asshown in Fig. 3. At thetank end the pipe enters asump which is fed from thetank through a needle -valve which, operated by aknurled knob, regulatesvery finely the flow ofmethylated spirit to theburners.

The sump can be made

or, if a greater quantity of spirit is requiredto be carried, it can be made to extend rightacross and fit up against the inside of thehull. If it is narrower than the hull it willbe necessary to provide some means ofholding it in position and in any case itwill be as well to solder a couple of strips ofplate on to its under side to serve as legswhich, with the sump, will provide a three-point support.

The Water TankThis is a simple box of sheet brass and

will, definitely, extend right across thevessel and be screwed, through lugs, to thewooden sides of the hull. As shown inFig. 4, it contains one of Bassett-Lowke'spumps of the pattern which is normallyused in locomotive tenders. This pump isconnected to the check valve at the forwardend of the boiler by a pipe, run along,outside of the boiler casing, on the portside.

No Filler CapNo filler cap or plug is shown on this

tank, the top plate of which must be maderemovable, because it is usually possible tofill with water through a tin funnel insertedin the slot through which the handle of thepump passes. If desired, however, a half -inch of brass tube may be soldered inanother part of the plate and a cork fittedinto this.

The LubricatorObviously some arrangement must be

made for sending tiny quantities of oil tothe engine continuously, whilst it is working,and the simplest way of doing this is by alubricator of the displacement type. Sucha lubricator can be made from a piece ofbrass tubing, a filling plug fitted at the topand a straight nose cock at the bottom. Aone -eighth -inch pipe is led into the top ofthe lubricator from the steam pipe andpasses down through the oil to within aneighth of an inch from the bottom, anotherpipe of the same diameter is led from thetop of the lubricator and is made to enterthe steam pipe lower down, see Fig. I.

SCALE'S FOR METRE, lueleTRE b ZMEIVE MODELS

I". I; I ICI

PtiS" 4 13

2" 21

2

5,

21 37

et I 11c6. 7, 03;

Fig. 4.-The water tank and pump.

from brass tubing and thetank of either tinned steel plate or sheetbrass, all soft soldered. The filler cap shouldbe screwed and, as before mentioned, accessto it is by the fore deck cargo hatch.

The width of the tank athwart ship is notindicated : it may be made square in plan

This lubricator may well be fixed on thestarboard side of the ship.

As a precaution against fire, or the affectsof heat, the whole hull is lined with Asbestosfrom the engine to as far as the forwardend of the spirit tank.


Facts About MetalsLiquid Gold.-Many of the so-called "liquid

golds " consist merely of a paint made upwith tin sulphide, which has a lemoncolour. True liquid gold, however;consists of a resinous compound of golddissolved in a mixture of essential oils.When coated on to pottery and fired in ahigh -temperature furnace, it produces abrilliant and imperishable film of gold,the exact colour of which can be variedby altering the composition of the goldcompound.

Likewise, aluminium paint is some-times spoken of as " liquid " silver,true liquid silver (or, more correctly,liquid platinum) is a similar compoundto the above but containing platinuminstead of gold. When fired in a furnaceit gives on pottery a brilliant, lustrouslayer of metallic platinum.

Lithitun.-Metallic element. Chemicalsymbol, Li; At. No. 3 ; At. Wt. 7 ; M.P.180° C.; B.P. 1400° C. Sp. Gray. .534 :Sp. Ht. .941 ; Elec. Cond. at 0° C. (Mer-cury=1) 10.69.

Occurrence : in many spring waters,and in a few minerals such as Lepidoliteor Lithium Mica. The metal was firstprepared in 1818 by Davy after itos oxide,lithia, had been discovered in the previousyear by A. Arfvedson. The metal wasnamed by the chemist Berzelius from theGreek, lithos, a stone, in significance ofthe hard stony minerals from which ithad been extracted.

Lithium is a silvery -white metal whenfreshly cut and having a slight yellowcast. Lithium metal is distinguished notonly by being the lightest of all metals,but, also, by constituting the lightestsolid material known. It floats on petrolwhich itself floats on water. Lithium canbe cut by a knife, but it is .harder thanits related metals, potassium and sodium.The metal may be pressed into wire, andtwo pieces of the metal may be made toadhere at ordinary temperatures bypressing them together. At a temperatureabove its melting point, Lithium takesfire and burns with a white light. Themetal decomposes water at ordinarytemperatures, evolving hydrogen andforming lithium hydroxide. Hencewhenexposed to moist air, it quickly becomescovered with a film of hydroxide. It isnormally stored under oil. Heated innitrogen, it forms lithium nitride.

Lithium metal is without use at thepresent day. Some alloys of the metalwith beryllium, aluminium, etc. havebeen made, but these are also useless.

Lutecium.-Metallic element. Chemicalsymbol, Lu; At. No. 71; At. Wt. 174.An extremely rare metal discovered in1907 by G. Urbain, and named fromLutece, an old name for Paris. It is agrey metal, similar to Ytterbium, butlittle is known about it.

MMackenzie's Amalgam.-This is a curious

amalgam, for, although it is normallysolid at ordinary temperatures, it becomesliquid by friction.

It is made by melting 2 parts of bis-muth and 4 parts of lead in separatecrucibles. The molten metals are thenthrown into two other crucibles eachcontaining 1 part of mercury. Whencold, these amalgams are solid, but they

(Continued from page 399 of June issue)

LIST OF ABBREVIATIONSThe following abbreviations are used throughout

this Dictionary :At. No.At. Wt. ..

Sp. Gray.Sp. Ht... ..Coef. Exp. ..Therm. Cond.Elec. Cond.

.. Atomic NumberAtomic WeightMelting PointBoiling PointSpecific GravitySpecific HeatCoefficient of ExpansionThermal conductivityElectrical conductivity

will melt when rubbed against each other.Magnalite.-An aluminium alloy of the

composition: aluminium, 94.2%; copper,2.5%; zinc, 0.5%; magnesium, 1.3%;nickel, 1.5%. It has a tensile strengthof about 30,000 lb. per sq. in. and aspecific gravity of 2.8. It is a light alloy,similar, in some respects, to " Y " alloy,and is of American origin.

Magnalium.-The name given to a groupof aluminium -magnesium alloys con-taining from 2 to 10% of magnesium.It is lighter than aluminium, and hasmechanical properties somewhat similarto brass.

The alloy is less corrodible than purealuminium and it can readily be turned.It has a greater tensile strength thanaluminium.

Magnet Steels.-Previous to 1930, the steelswhich were able to be magnetised themost powerfully were those containingvarious amounts of cobalt, the " cobaltsteels." In 1930, however, a new seriesof magnet steels was discovered in Japan.the principal alloying ingredients ofwhich were aluminium and nickel. Manyof these special steels were made andinvestigated, the most important onecontaining 13% of aluminium and 25%of nickel alloyed with steel. Such steels,however, are now being superseded bythe new aluminium -nickel -cobalt steelnamed Alnico " (which see).

Magnolia Metal.-A white metal alloy forbearings. Has been used chiefly inmarine and railway work, since it standswell up to heavy bearing pressures.Composition : lead, 78% ; antimony, 16% ;tin, 6%. The metal takes its name fromthe trade -mark of its original manufac-turers-a magnolia flower.

" Tandem metal has a similarcomposition.

Malleability.-The degree to which a metalcan be flattened out in all directions byrolling or hammering. The malleabilityof a metal depends upon its toughnessand, also, upon its tensile strength.Metals having coarse crystalline struc-tures are not malleable. Hence, anyimpurity in a metal or any mechanical orphysical action to which it is subjectedwhich results in an increase of its coarse-ness of grain or crystalline structure willdecrease its malleability. Some metalsincrease in malleability with increase intemperature. Gold is the most malleableof all metals, it having been beaten intosheets no more than .000004 in. thick.

The following well-known metals arearranged in order of decreasing malle-ability: gold, silver, copper, tin, platinum,lead, zinc, iron, nickel.

The relative malleability of metals isa measure of the thinness to which theymay be reduced from the same thickness.

(From the Latin, mallene, a hammer, in

reference to the hammering or beating ofmalleable metals.)

Manganese.-Metallic element. Chemicalsymbol, Mn; At. No. 25; At. Wt. 55;M.P. 1245° C.; B.P. 1900° C.; Sp. Gray.7.3921; Sp. Ht. .1217.

The metal was first prepared by Galuaabout the beginning of the last century.It was derived from magnesia nigra, or

black magnesia " (as manganese dioxidewas then called) and, accordingly, thenew metal was given the name of" manganesium," which was afterwardsshortened to " manganese " to avoidconfusion with " magnesium," anothernew metal.

The chief ore of manganese is pyrolusiteor black manganese dioxide, Mn02.

Pure manganese is a white -grey,lustrous metal having a slight reddishtinge. It is harder than iron and willtake a high polish. The metal is brittleand is superficially oxidised when exposedto moist air. Heated in nitrogen orammonia gas, it forms manganese nitride.The metal is soluble in inorganic acids.

Added in small amounts to steel,manganese exerts a very pronouncedhardening and toughening effect, hencethe nowadays numerous "manganesesteels." The pure metal itself, althoughby no means rare, is more or less acuriosity at present. Its best-knowncompound, manganese dioxide, has beenused since the times of the Romans fordecolourising or " bleaching " glass.Potassium permanganate is anotherwell-known compound containing man-ganese.

Manganese Bronze.-This is a form ofbrass containing about 60% of copperand 40% zinc, together with a littlemanganese and iron. Typical composi-tion : copper, 56; zinc, 41.5 ; manganese..25; aluminium, .25; iron, 1 ; tin, 1. Ithas a tensile strength of about 30 tonsper sq. in. and is, therefore, as strong asmild steel, in addition to being tougherand more resistant to corrosion. It issometimes (although less accurately)known as Manganese Brass.

Manganese Copper.-Also known as Cupio-manganese. Name given to a number ofcopper -manganese alloys of varied pro.portions. They are silvery -white incolour, have great hardness and fairductility. The best manganese copperscontaining from 10% to 30% of manga-nese. A typical manganese coppercontains: manganese, 25%; copper, 75%.Other varieties of this alloy containsmall amounts of tin, zinc and nickel.It often serves as an addition to copperor copper alloys in order to impartgreater strength and density to them.

Mannheim Gold.-One of the many " imi-tation golds." Composition: copper,83.1 % ; zinc, 10.0% tin, 6.9%. Thecomposition of Mannheim gold variesconsiderably, and sometimes the tin isleft out. It has a reddish tint.

Also known as " Similor " and "Prince'sMetal."

Martensite.-Name given to a solid solutionof carbon in that variety of pure ironknown as " beta -ferrite." It is a typicalconstituent of steel which has beenhardened by quenching. Called after A.Martens, the metallurgist.

(To be continued)

456 NEWN ES PRACTICAL MECHANICS July, 1940

"MOTILUS" PEEPS INTO THE

An attractive "0" Gauge indoor layout built by Mr. Ray Coomer

An Actor and His HobbyWHEN in Northampton recently,

Mr. Bruce Carfax, the well-known singer and musical comedy

star, was able to renew acquaintance withan old hobby of his-that of model rail-ways. With several other interested mem-bers of his company, including Miss DorisFrancis, who plays Nadine to his Bumerli

in The Chocolate Soldier, Mr. Carfax spentan afternoon at the Bassett-Lowke modelworks, and took a keen interest in thetechnicalities of model -making. Duringhis visit he related quite a few modelrailroader's yarns. A few years back heowned a flat in Hampstead which waspractically bought so that he could planout a model railway. A room 23 ft. by18 ft. 3 in. was devoted to it, in which hedevised a most extensive system, whichran up two levels, so that the trains circledthree times round the room before mountingto the highest point of the railway. Amongits novelties were a starting hump andthree attractive stations. One was designedon the lines of the Manchester Exchangestation, while another-his prize piece-was over six feet in length and built

specially to follow the curve on the " secondfloor " of the system.

The railway was gauge " 0 " electric,with steel permanent way, and for fouryears it gave him, and quite a number ofhis friends, a hobby to be enthusiasticabout.

Mr. Carfax remarked on the surprisingnumber of actors who are interested in

A miniaturesteam enginebuilt by Mr. C.Mansford, a

watch -maker

models. He mentioned Owen Nares,Gene Gerrard, and also Jack Hulbert'sgauge 1 garden railway, which is, inci-denten+, quite famous throughout theprofession.

A Fine LayoutVisiting the south coast of England

recently I came across a very fine gauge" 0 " indoor layout in the basement of theTarrazona Hotel at Boscombe. It wasbuilt by Mr. Ray Coomer, son of theproprietor, and the layout consists of 75 ft.of double track with twelve points, athrough station, girder bridge constructedfrom curtain rail, a five-foot tunnel made ofa wooden frame and covered with a sugarsack and coated with a plastic material,suitably coloured. The turntable is electri-cally operated and is automatic, and thewhole layout is on baseboards bracketedto the wall, four feet high from the floor.There are three express locomotives,G.W.R. King George V, L.M.S. PrincessElizabeth, and L.N.E.R. Flying Scotsman,and also one G.W.R. 2-6.2 tank and aUnion Pacific Diesel electric, thesebeing 20 volts a.c. Among his rolling

A model of S.S. Cynthia constructed entirely of scrap metal


MODELWORLD

stock. Mr. Coomer owns five G.W.R.coaches, which when hauled by the " Kffig "make a model of the Cornish Riviera, thewhole being illuminated, including the locowith scale headlamps and fire box glare.There are also five L.M.S. -Coaches, hauled

Aircraft Models ; WorkingMiniatures ; Models FromScrap ; A Railway in a

Hotel Basement

by the Princess Elizabeth, and 35 goodswagons. A most interesting feature of theline is the application of a. scenic back-ground. This has been cleverly built upfrom cut-outs from various posters-mostlyrailway posters, and although the itemswhich appear in the background have noreal relation to each other in topography-the tout ensemble is very attractive butthose who are sticklers for accuracy ofsituation will understand that althoughLichfield Cathedral appears near the cliffsof Dover. it is just a matter of artisticlicence !A Miniature Steam Engine

A friend of mine from Minneapolis,knowing my penchant for models andphotographs, has sent me an illustration

Mr. Bruce Carfax, the well-known actor, who recently paid a visit to the Bassett-Lowke modelworks. He A a keen model railway enthusiast

,J. L. C. Dickson, and is unique in that it isconstructed eritirely from scrap material.It is 2 ft. 9 in. overall by 51 in. beam widthand 41 in. to shelter deck. The shellplating, the whole of which is riveted toside frames following closely the orthodoxtype of passenger cargo vessel, was madefrom old tins. There are two bulkheadifore and aft of the midships section. ' Therivets were from brass as used by bootrepairers. The three -bladed propeller was

A model "Spitfire" built from an Aeromodeis kit

of a miniature steam engine. It was builtby Carl Mansford, a watch -maker, of brass.bronze and steel, and can be operatedeither by steam or compressed air. It isamazing when you think that its smallboiler is strong enough to withstand atleast a 30 -pound pressure. There is agauge on the boiler registering up to 20pounds, and the engine reaches 250 revolu-tions per minute at average speed. Thebase is 13 in. by 9 in. The boiler is 4 in.by 8f in. and the engine is in. bore by11 in. stroke. There are 7 jewelled bearingsin the engine, five in the governor and twoin the pressure gauge. The engine itselfis gold plated and contains between 450and 500 pieces altogether-a wonderfulexample of the craftsman's art in miniature.Model from Scrap Metal

The _model of S.S. Cynthia illustrated,is the work of a. Chelmsford amateur, Mr.

shaped from an old brass sink plug ! Theports are brass washers riveted throughshellplate and glazed with old film negative,as likewise the saloon windows and chart -house: The ship's bell is hand -made fromsolid brass. The crew's accommodation inthe forecastle is fully furnished, as is theofficers' and passenger accommodation onmaindeck and poop. The masts are of wood,the funnel of copper tube and all fittingsare made from scrap. The owner hashanded the model over to the EssexComforts Fund for the period of the waxand it is on view to the public in thevestibule of the Public Library.Model " Spitfire "

An illustration of an R.A.F. Spitfire,modelled to scale from an AEROMODELSkit (as sholvn on this page). It is the workof a young school -boy amateur, who startedthe hobby only seven months ago. He hasbuilt mainly duration models and the" Spitfire is his first attempt at a scalemodel. It took forty-five hours to buildand is camouflaged khaki and green forground protection, and the underside ispainted silver, which would make theprototype more difficult to follow when inthe air. This " Spitfire " model can eitherbe built with large propeller as a workingmodel, or as in the illustration, with scalepropeller, for display.

Showing the model "Spitfire" ready for covering


LIGHT -GIVING MINERALSSome Curious and Little-knownExperiments with Luminescent

Minerals and Crystals

THE fact that certain chemical sub-stances are capable of giving out apeculiar " cold light " of their own

is a well known one. Phosphorus, forinstance, has long been famous for theghostly greenish -blue light which it emitsin the dark, and nowadays, of course, certainlight -giving materials, notably the sulphidesof calcium and zinc, have obtained con-siderable commercial importance in themanufacture of luminous paints, and otherphosphorescent preparations.

In spite of the fact that many of theseself -emitters of " cold light " have beenknown for very long periods, their inherentmode of action still constitutes one of theminor mysteries of science. We do notknow for certain why calcium and zincsulphides fail to luminesce when they areperfectly pure but shine often with con-siderable brilliance when they are in-timately mixed with certain traces of con-taminating substances.

Most of the common luminous materialsfrom which the various phosphorescentpaints are made seem to act as accumu-lators of light. When exposed to a brightlight, they appear to take in a large amountof light energy, and to give it up again inthe form of their characteristic luminescenceover lengthy periods. If; however, suchlight -activated materials are permanentlykept in the dark there comeka time whentheir luminescence fails, such materialshaving apparently given up all their storedlight energy. But when these substancesare again exposed to strong light for two orthree minutes they become, as it were,recharged with light energy, and, as aresult, they are once more able to shinein the dark with their accustomed brilliance.

" Luminophores "Materials of this nature have, within

recent times, received a new categoricname-" lummophores." Thus calcium andzinc sulphide are typical luminophores,since they are, in some strange, and as yetnot satisfactorily explained way, able tostore up light and afterwards to re -emit itin the form of luminescence.

Calcium sulphide (which has been knownfor upwards of two centuries as " Canton'sphosphorus " was at one time obtained bystrongly heating a mixture of two parts offlowers of sulphur, and one part of finelycrushed oyster shells. It may still beprepared in this manner, although a betterresult will be obtained by heating to redheat a mixture of two parts of sulphur, onepart of finely powdered lime and approxi-mately one-half part of starch. Theseingredients should be intimately mixedbefore heating, and a trace of bismuthnitrate should be added to the mixture. Themixture is best' eated in an old tin which,with its lid on, is placed in the middle of abright -red fire. A small vent should be

made in the lid of thetin in order to permitthe escape of the sur-plus sulphur fumes.

A creamy -colouredpowder will resultfrom the above oper-ation. After beingexposed to sunlightor to a strong artificial light, it will lumin-esce with a violet light. By substitutinglead acetate or lead nitrate for the bismuthsalt in the above formula, the luminescenceof the finished product will be yellow -green,whilst traces of uranium, mangangse or zinc,give bluish, orange or greenish luminescencesrespectively.

Calcium sulphide luminous powder pre-pared in the above manner may be in-corporated into a paint or varnish, theproportion of the luminous powder in thepaint being from 5 to 15 per cent. The paintshould not contain any white lead, other-wise the luminescent property of thecalcium sulphide will rapidly deteriorate.Usually, clear varnishes of the cellulosetype are the most suitable for making upthese calcium sulphide luminous paints

Making luminous powder by heating lime, sulphurand starch in an old tin held in the fire, as

explained in the text

Examples of fluorspar, which becomes strongly luminous when heated

and if such a paint be brushed on to asurface which has previously been paintedwith a leadless white paint the maximumdegree of luminescence will be forthcoming.

So much, therefore, for the subject ofluminous paints. It is a subject to whichmuch scientific attention has been paid inrecent times and although many excellenttypes of " luminophores " are now on themarket, the ideal long-lasting brilliantlyluminescing material has yet to be found.' Quite apart, however, from the well-

known variety of luminescence describedabove, there are several other types oflight -emission by minerals and crystalswhich are not generally known, but which,although they are, perhaps, incapable ofbeing commercialised, present, at least, afield of interesting experimental activityto the amateur investigator of such pheno-mena.

FluorsparPerhaps the most remarkable type of

mineral luminescence is that exhibited bythe well-known mineral fluorspar, which,under the name of " Fluorite," " BlueJohn," and other titles occurs in severallocalities of Britain.

When almost any variety of fluorsparis powdered up in the dark it emits a brightpurple light, which, now and again, may beseen lingering over the mineral as a luminoushaze, even after the powdering operationhas been completed.

A better way to observe the luminescenceof fluorspar (and that of some other typesof minerals, as well) is to fling the powderedmaterial on to an iron plate in the dark,the plate being heated to a temperaturejust below that of dull -red heat. On makingcontact with the heated plate, the powderedfluorspar will emit a brilliant phosphoriclight which will usually be a vivid violet incolour. Certain varieties of fluorspar,however, will, under the above conditions,give forth an orange, blue and even apinkish light, although the average fluorsparspecimen will produce the characteristiclivid violet luminescence which will last forseveral minutes before it dies away com-pletely.

Other minerals besides flourspar givesimilar results when thrown on to a heatedplate in the dark. Certain varieties ofcalcite (calcium carbonate) and calcareousspar shine strongly with a yellow lumines-cence, whilst anatase will often give riseto an exceptionally striking effect, appear-


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LEARN RADIOFROM A to Z

am wati ow. EN. ow...... vim moo m. am am on 1i

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(1) THE OUTLINE OF WIRELESSBy RALPH STRANGER

This book covers the theory and practice of WirelessReception from A to Z, and makes everything plain even tothe most " non -technical " reader. Step by step, it teachesyou everything you want to know about wireless. Over800 pages, fully illustrated. 10s. 6d. net. (By post 1 1 s.)

(2) THE PRACTICAL WIRELESSENCYCLOPAEDIA

By F. J. CAMMWireless Terms and Definitions stated and explained inconcise, clear language. 392 pages. Over 500 illustrations.

7s. 6d. net. (By post 8s.)

(3) EVERYMAN'S WIRELESS BOOKBy F. J. CAMM

A radio Consultant for the Listener, Expert and AmateurConstructor, with Special Chapters on the Principles ofRadio Telephony, Installation and Systematic Fault-finding. With 200 Illustrations and Diagrams.

5s. net. (By post 5s. 6d.)

(4) SIXTY TESTED WIRELESS CIRCUITSBy F. .1. CAMM

Modern circuits of every type. Diagrams and instructionsfor assembling and wiring. Details of components andnotes on operation.

3s. 6d. net. (By post 4s.)

(5) PRACTICAL WIRELESS SERVICE MANUALBy F. J. CAMM

A complete work on the testing and servicing of all typesof wireless receivers. Packed with information. Withover 220 illustrations. 228 pages.

6s. net. (By post 6s. 6d.)

(6) NEWNES' SHORT-WAVE MANUALBy F. J. CAMM

Deals thoroughly with the problems underlying the designof short-wave apparatus, the special circuits which yieldthe best results, and designs for receivers based on thosecircuits. 5s. net. (By post 5s. 6d.)

(7) WIRELESS TRANSMISSION FOR AMATEURSBy F. J. CAMM

Covers fully and clearly the whole field of wireless trans-mission. With 120 illustrations. 3s. 6d. net. (By post 4s.)

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Street, Strand, London, W.C.2.

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ing to burst into a white flame and to emitwhite flashes of light.

ZeolitesSome of the zeolites, such as harmotome,

will shine under these conditions with agreenish -yellow' hue, whilst the semi-precious gem, topaz gives a bright bluecolour.

It is interesting to subject any mineralto the above test, since even the commonestof minerals will, at times, particularly whencontaminated with certain metallic sub-stances, give rise to vivid and strikingresults of a luminescent nature.

Exactly why and how these effects areproduced no one knows. Nor do we knowwhy some minerals emit light when they aremerely struck with a hammer, and, in someinstances, even scratched with a knife.

Certain varieties of zinc blende, a commonenough mineral, will, when sharply scratchedwith a knife or powdered up in a mortar,produce a soft yellow luminescence, whilstmany of the pebbles of milky or translucentquartz which are to be found in greatnumbers on almost every seashore willfrequently give out a bluish light whenstruck or rubbed briskly together in adarkened room. It is a strange fact thatthis emission of light will take place evenwhen the pebbles are sharply rubbedtogether under water.

ChlorophaneChlarophane is not a common mineral

but it is to be found in some districts.So sensitive is this mineral to heat, that itwill actually shine in the dark when throwninto a basin of hot water. Furthermore,the green variety of chlorophane will some-times become luminous merely by holdingit in the palm of the hand in a darkenedroom.

Another interesting type of luminescencewhich is, as yet, altogether unexplained, isthat exhibited by the mineral, mica. Whenmica is split up into its well-known thinsheets in the dark, it gives a faint yetclearly distinct glow at each cleavage ofsheet from sheet Certain of the felsparminerals produce a similar result, althoughnot with the same constancy as mica.Even household sugar, when powdered inthe dark, sometimes becomes luminous.

The native sulphide of antimony, knownas Stibnite, will often become vividly in-candescent when heated to a temperaturejust above that of red heat, although itsrelated lead compound, galena (lead sul-phide) invariably fails to show this effect.

Rochelle SaltIn the realm of crystalline substances

there are to be found some very mystifyingexamples of luminescence. When, forexample, - Rochelle salt, which is sodiumpotassium tartrate, is dissolved to form astrong aqueous solution, and this solutionis boiled in the dark, it will be seen to giveoff copious showers of violet -blue sparks.These sparks are, of course, quite cold,and they may be allowed to impinge uponthe hand without harm.

Again, when ordinary boric or boracicacid is fused in a crucible and, after becom-ing almost red hot, is allowed to cool downin a darkened room, the molten masssolidifies, splits and cracks as its tempera-ture falls. During these splittings andcrackings, the acid will often be observed tothrow up very bright flashes of greenishlight which are, at times, almost electricalin their brilliancy.

Vanadic acid gives rise to a similar effect,but here the phenomenon is more intensified,for, after fusion, the material shines with an

orange -red light which persists throughalmost the entire period of its crystallisa-tion.

Sodium FluorideAnother exceedingly mysterious pheno-

menon of crystal luminescence is thatexhibited during the crystallisation ofsodium fluoride. This is a perfectly whitesubstance which when dissolved in water soas to form a saturated solution and then setaside in a darkened room to crystallise,produces a brilliant luminescent twinklingor scintillating effect as each individualcrystal forms from the solution. Fewindividuals have taken the trouble toobserve this effect. Yet it is quite a brilliantone and, up to the present, it has neverbeen explained.

Although none of the above luminescenteffects have ever been satisfactorilyaccounted for, some attempt has, in thepast, been made to classify them. Thus,

Dropping powdered fluorspar on to a heated ironplate in a darkened room in order to witness its

production of luminescence

the luminescence of minerals caused byheating is termed " thermo-luminescence,whilst that derived from the crushing orother mechanical disintegration of themineral is known as tribo-luminescence."Certain types of luminescence broughtabout by chemical means are known as" chemo-luminescence," and there are, also,some varieties of luminescence known as

electro-luminescence." These latterphenomena are usually brought about bysubjecting the mineral or crystal to theinfluence of an electric discharge. Forexample, if a quantity of barium sulphatehas an electrical discharge from an inductionor sparking coil transmitted along itssurface, it will develop a very characteristicgreenish -yellow glow. Potassium acetatecrystals will, under these conditions, shinewith a brilliant green light, whilst anordinary rock crystal will develop a dull redlight which will gradually become whitish.

In many instances, too, these effects donot cease immediately the current isswitched off. On the contrary, they persistfor several minutes after the exciting current has ceased to flow.

Exposed to X-, and, also, to cathode rays,a large number of minerals and crystalsglow vividly in characteristic colours. Suchexperiments, however, are usually beyondthe resources of the average amateur, andhence there will be little import in describ-ing them further.

Yellow PhosphorusThe well-known luminescence or phos-

phorescence of yellow phosphorus is simplyan effect of oxidation, the light beingproduced as a result of the element's slowoxidation by the oxygen of the air. Thus,if phosphorus is placed in a vacuum or ina gas devoid of oxygen, it at once ceases toglow. Curiously, also, if phosphorus isplaced in slightly compressed oxygen, italso refuses to glow, and furthermore, ithas been definitely proved that if perfectlydry phosphorus is placed in perfectly dryair, it will not shine in the dark.

Ordinary luminous paints which are, forthe most part, composed of calcium or zincsulphides, specially prepared and treatedso as to heighten their luminescent powers,will glow undisturbedly under almost anyreasonable conditions. Having been

activated " by exposure to strong light.they will thereafter continue to glowsteadily in air, in a vacuum, under water,or in an atmosphere of an inert gas for manyhours, until their absorbed light -energybecomes exhausted. Subsequent " re -activa-tion " by again exposing them to stronglight will re -charge them with light energyfor another period, and, usually, providedthat reasonable care is taken to prevent the" luminophore," or luminous material.from becoming contaminated by dirt orextrinsic impurities, this cycle of absorptionand emission of light energy is capable ofbeing repeated almost indefinitely.

Light AccumulatorsCuriously enough, the above process

represents the only means of actuallystoring -up light which we know of. It isthus extremely tantalising that it should be,in practice, so ineffective a mode of °pewit -ing this fundamental principle, for were itpossible to devise large-scale " light -accumulators " and, to charge them dailywith the sun's light so that, in the dark, theyemitted rays of equal intensity then thelong sought -for solution of the problem of

cold light " would be at hand, and thenecessity for' utilising all our present-daytypes of electric and other artificial illumina-tion would be no more.

Perhaps one day such a solution will beforthcoming. For, as the reader who hasstudied this article will now be aware, thereare many rudimentary types of " mysticmineral light " whose inherent nature weare, as yet, unaware of, but the furtherexamination of which may, at long last,implant in the mind of the serious experi-menter that essential clue to the com-mercial production of an efficient andutilitarian " sunlight accumulator " whichwill bring him certain fame and, also, veryprobable fortune.

WORKSHOP CALCULATIONSTABLES AND FORMULIE

2nd Editionby F. J. CAMM

A handbook dealing with methods ofcalculation, solution to workshop prob-lems, and the rules and formulme neces-sary in various workshop processes. Itcontains all the information a mechanic

normally requires.

From all booksellers, 316 net,by post 3,10 from the publisher:

GEORGE NEWNES LTD. (Book Dept.),Tower House, Southampton Street,

London, W.C.2.


QUERIESG,A4`;'fr\ii ENQUIRIES

.4nti-gas Paint

WHATis the formula for the "anti -gas"

paint used on the wooden pedestalsthat are dotted about the country ?-A. D. (Luton).

THE"anti -gas" paint which is at present

so widely used for painting on the topsof pillar boxes, etc., is more or less of secretcomposition. It turns red on contact withmustard gas, but, at the same time, othersulphur -containing organic substances willexert the same effect.

You may, however, prepare a similarpaint by grinding up copper mercuriciodide with varnish. A mixture of cuprous(copper) iodide and mercuric iodide has asimilar effect. All such materials may beobtained from Messrs. Harrington Bros.,Ltd., Oliver's Yard, City Road, Finsbury,London, N.1.

Whitening Concrete

PLEASEtell me the preparation to whiten

concrete pillars used in bay windowsand the porch of a front door.-W. C.(Coventry).

A LMOST any white colour -wash maybe used for the purpose you name. We

presume, of course, that you do not wishactually to paint the stone surfaces, andhence we would recommend for your atten-tion a good white distemper, such as maybe purchased at any colourman's shop forabout 2s. 6d. per 4 lb. tin. This quantityshould be sufficient for the purpose youname.

If you do not wish to purchase a ready-made preparation, you can make up yourown colour -wash by obtaining 2 lbs. ofceiling white and by mixing this to a thinpaste with water in which a small quantityof size has been dissolved.

All preparations of this nature should bebrushed on to the stonework thinly. It isbetter to apply two or even three thincoats than to apply merely one thick coat,which latter may flake off, and, in any case,wash off with the rain.

By brushing over your whitened surfacewith a solution of formalin (1 part formalinto 20 parts of water) the surface will berendered almost completely waterproof.

Engine for Model Cargo BoatI N the article on building an engine for a

model cargo boat which appeared in ourMarch, 1940, issue the cylinders are shownin the sectioned views, Fig. 1, with theirinner ends merely passing into the crank-case. Actually the fixings should have beendrawn in the elevations and plan, Fig. 2,and a correcting sketch is here given to putthe matter right.

Each cylinder is provided with two lugsthrough which screws pass into the crank-case. Each lug should embrace at leasta quarter of the circumference of eachcylinder and should be silver soldered on.

A stamped addressed envelope, three pennystamps, and the query coupon from the currentissue, which appears on page iii of cover, must beenclosed with every letter containing a query.Every query and drawing which is sent must bearthe name and address of the sender. Send yourqueries to the Editor, PRACTICAL MECHANICS,Geo. Newnes, Ltd., Tower House, Southampton

Street, Strand, London, W.C.2.

Making Windows Splinter ProofWILL a celluloid solution if painted onwindows prevent splinters due to blast

from explosions, and if so, what is the com-position of such a solution ?

Would such a solution "flake off" whenexposed to the heat of the sun, and is it stillinflammatory after application.

Would the cost be prohibitive ?-W. S.(S.W.9).

I F the window -panes in question aresituated just on the "effective fringe" of

an explosion area, it is very probable thatthe presence of a celluloid layer on theglass would prevent the fracture of thelatter. If, however, the panes were withinthe range of an explosion the celluloidlayer would have no safety effect what -

A "Wind Charger"I HAVE a Morris 12 v. 4 -pole dynamo -

motor which I want to use as a "windcharger." Is it necessary to rewind thearmature, and if so, what quantity and gaugeof wire will be required ?-L. G. (NorthWales).

BEFORE it is possible to issue windingspecifications for either dynamos or

motors to give specified outputs, it isessential that the following details aregiven :-

(1) Size of armature (diameter, length, andnumber of slots).

(2) Particulars of commutator (numberof bars).

(3) Number of field magnet poles, andtheir dimensions.

(4) Number of brushes, and their angulardistance apart.

If these data are supplied a suitablewinding can be got out to give the desiredoutput.

An Electric FenceHOW can I make an electric fence and

how is the periodic impulse produced ?-R. J. (Co. Kerry).

THE principle on which these operate isto employ a high-tension transformer of

small output capacity, fed with currentfrom a low -voltage accumulator. A slow -speed interrupter is used in the primarycircuit, generally of the rotary balance wheeltype, which gives periodic interruptions tothe primary and causes a sharp shock toanything touching the communicating wiresof the fence. The fence itself consists of

31111611E010 11..\\`11 \NOM

Pe

Method of fixing cylinders of the engine for the model cargo boat.

ever, and we doubt whether it would evenprevent the glass from shattering intosplinters.

A suitable celluloid solution for applica-tion to glass can be made by dissolving scrapcelluloid in a mixture of 2 parts acetone and1 part amyl (or butyl) acetate. To theresulting solution, which should have theconsistency of thin paint, a few drops ofcastor oil should be added.

The solution is, of course, highly inflam-mable, but, after drying on the glass, theresulting film of celluloid would hardly burnif ignited. The celluloid layer thus depositedon the glass will not subsequently flake off,provided that the solution contained therequisite very small amount of castor oiland, also, provided that the glass wasscrupulously cleaned before the applicationof the solution.

The cost of treating the glass would not beprohibitive, and for an outlay of, say, 5s.in material, you should have enough solu-tion to treat several windows. Amyl andbutyl acetate, and also acetone can beobtained from Messrs. A. Boake, Robertsand Co., Ltd., Stratford, London, E.15.Scrap celluloid is available from most filmrenters, etc.

plain wooden posts with a single wire inconnection with the high tension side of thetransformer, at such a height that the cattlecan neither creep under nor jump over itwithout touching. No doubt a make-shift device could be developed using an oldcar ignition coil, but it would have to befitted with a special slow -speed interrupter,either in the form of the balance wheel of awatch or with the usual oscillating motionslowed down to about 90.120 contacts perminute by counterweighting the tremblerblade. The whole apparatus is marketed byThe Harvest Saver & Implement Co., Ltd.,77, Queen Victoria Street, London, E.C.4.

HydrocultureI AM interested in the new " tank garden-

ing," and while I find there have beennumerous references made to it in variouspublications, detailed information seemsdifficult to obtain.

I have a number of tanks each about afoot square and wish to grow tomatoes inthem.

Could you tell Me what chemicals wouldbe required and in what quantities eachshould be used in a gallon of water ? How


Skill we'llrepaid

when yo useVARNENE

OIL VARNISH STAINDo full justice to your woodwork by givingit a fine high gloss finish with Vamene, theoil varnish stain, which will not readily chipor scratch. Varnene is far easier to applybecause it never becomes tacky while working

From Handicraft Stores, Ironmongers, Oil-men, Grocers & General Dealers, In DarkOak, Walnut, Mahogany, Light Oak, EbonyBlack and Clear (Colourless) Varnish.

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STUARTMODELSWe regret

that we can no longersupply our model goodsbecause our Worksmust now be entirelydevoted to work forthe Government service.

We hope that happiertimes will soon comewhen we shall be againable to advertise ourgoods to the readers of"Practical Mechanics"

STUART TURNER LTD.Henley - on - Thames

deep should the water be in each tank andshould tomato seeds be sown or will plantssuffice ?-J. S. (Teignmouth).

YDROCULTURE "-the growing of1 plants in water containing nutrient

substances-is a fairly ' new branch ofhorticulture, but, so far, this form of" tank gardening " has not had very muchpractical success.

Seeds, of course, will not germinatesuccessfully when placed under water; it isonly with young plants or seedlings that themethod of tank gardening " is, in someinstances, applicable.

Many varied solutions have been pro-posed for tank gardening. They all differin the proportions of their ingredients.The following formula, however, will befound to be as good as any of them.

In two gallons of good clear water(preferably rainwater or water free fromlime or chalk) dissolve

Ammonium sulphate ..Potassium sulphate ..

chloride ..carbonate ..

Sodium sulphateIron sulphate ..

f oz.

1/16 1/64 1/64 1/64

Magnesium chloride .. 1/64 oz.sulphate ..

Ammonium phosphate--1/32 1/32

Sodium phosphate .. 1/32Potassium phosphate .. 1/32

The resulting solution is the one in whichthe plants are grown. Only the roots ofthe plants should be immersed in thesolution, and if the latter tends in any wayto become mouldy, it should be thrownaway and replaced by fresh solution.

Plants growing in liquids such as theabove must be very carefully supportedand must not be given too much sunlight,otherwise they will yellow and die.

Note, also, that solution -cultured plants,especially those of the very soft -stemmedvarieties are very likely to contract diseasesand to die on that account.

THE P.M. LIST OF BLUEPRINTS

F. J. CAMM'S PETROL -DRIVENMODEL MONOPLANE

7s. 6d. per set of four sheets, full-size.The "PRACTICAL MECHANICS" L20 CAR

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"PRACTICAL MECHANICS" MASTERBATTERY CLOCK

Blueprint Is.

The "PRACTICAL MECHANICS" OUT-BOARD SPEEDBOAT

7s. 6d. per set of three sheets.A MODEL AUTOGIRO

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Full-size blueprint, Is.The P.M. "PETROL" MODEL

MONOPLANEComplete set, 5s.

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Full-size blueprint of wing sections, 6d.LIGHTWEIGHT DURATION MODEL.

Full-size blueprint, 2s.

P.M. TRAILER CARAVANComplete set, 10s. 6d.

The above blueprints are obtainable post free fromMessrs.G.Newnesltd.,TowerHouse,Strand,W.C.2

'PELMANISM1914 and 1940

DURING 1914-1918, the Pelman Institute, in London and throughout the

Empire, made a real and important con-tribution to the efficiency of the nation.The value of Pelmanism as a training inpersonal efficiency was freely acknow-ledged by leaders in the military andnaval forces, as well as by those carryingout the highly responsible civil workwhich the exigencies of the time demanded.During the Great War, no fewer than 160Admirals and Generals studied the PelmanCourse, and their example was followed byover forty thousand other officers and menthroughout the Services. Good as Pelmanismwas in 1914-18, it is very much better in1940. Added knowledge and experiencehave made it so.

Your ObligationThe success of Pelmanism as a personal

training is due to the amazing adaptabilityof the Course to the particular needs ofthe individual, whatever his circumstances.

Half fees for all serving members ofHis Majesty's Forces

To -day there is an obligation upon everyman and every woman to make the maxi-mum contribution to the task which theEmpire has undertaken. There is a demandfor organising ability, clearness of vision,concentration, and the ability to resistdistractions; there is, above all, a need,such as has never before been felt, for level-headedness and resourcefulness. The Pelmu ndiscipline establishes self-confidence,quickens the perceptions and 'promotespersonal initiative.

Remember this-Everything you do ispreceded by your attitude of mind.Pelmanists are not left to make the

applications themselves. An experiencedand sympathetic instructional staff showsthem, in exact detail, how to apply theprinciples of Pelmanism to their owncircumstances and aspirations. Thus everyPelman Course is an individual Course.Over and over again our correspondentssay, in effect, "I feel that this Course wasprepared for me, and me only." Substan-tially this is so, for the instructional notesand letters of advice are entirely personalto the individual.

The world of affairs demands courage.Not the blind, reckless plunge that is mere'bravado, but the calm, self-reliant couragebefore which obstacles recede. This meansthe foresight and forethought which Pel-manism confers on all who take the Course.

The revised Pelman Course is fullyexplained in " The Science of Success." TheCourse is simple and interesting, and takesup very little time. You can enrol onthe most convenient terms. The bookwill be sent you, gratis and post free, onapplication to -day to :-

Pelman Institute(Established over sw years)

130 Pelman House, Bloomsbury StreetLondon, W.C.I.

Read.. rtho air call at the Institute mill be welcomed. Th.Director of Instruction milt be pleased to Mee a talk with

thee, and so fee tell be charged for Al, advice.

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July, 1940 THE CYCLIST

THE

) 1:'

Editor F. J. CAMM

VOL. IX JULY, 1940 No. 221

Comments of the Month

A Sign of the TimesI T is a sign of the times that signposts and

milestones are, for the duration of thewar, withdrawn. Our roads now take on ananonymous aspect, making travel difficultfor the traveller unaccustomed to touring.Some of these old milestones are historic,and it seems a pity that they should bedefaced by cement instead of being removedand replaced after the war. In most casesit will be impossible to remove the cementand thus these ancient milestones will bereplaced by new ones. They provided auseful road measure for time trialists, andnow that they have gone, the difficulties oftime trials organisers have been increased.It means that more marshals will have tobe employed to prevent riders straying fromthe course. Many instances have occurredalready where fast riders have gone off thecourse and been put out of the trial. Theobliteration of all signposts and directionsigns will undoubtedly have a marked effecton touring, for individuals on bicycles whofrequently stop to ask the way are likelyto be suspected of fifth column activities.Still, it is in the interests of Home Security,to which the needs of sport must necessarilybe subjugated.

War Effort and the SportROAD sport is being affected in another

way. Holidays have been cancelled,and some thousands of cyclists are workingovertime each evening as well as Saturdayafternoons and Sundays. This removes theopportunity for practice spins and makes itpractically impossible to run week -endevents. Already clubs are complaining ofdepleted entries. The R.T.T.C. has notgiven any lead to the clubs as to whetherthey should cancel their events in view ofthe Government decision to cancel holidays.The position seems to be that individualclubs will be left to organise events if theycan. This is a policy with which we entirelyagree. Some clubs have cancelled theirevents. The Bath Road Club will hold itsfamous " 100 " on the Sunday instead ofAugust Bank Holiday.

Marguerite Wilson AgainMISS MARGUERITE WILSON, riding

a Claude Butler bicycle with Sturmey-Archer hub gear, secured the Birminghamto -London W.R.R.A. record on Sunday,June 9th, beating the present holder MissBiggs' record by nearly 7 minutes. This inspite of the fact that she elected to ridefrom London to Birmingham which pro-vides a slightly more difficult course thanriding from Birmingham to London. MissWilson's last two records were the Land'sEnd to John O'Groat's and the 1,000 mileswhich she broke on the outbreak of war.Her present success demonstrates that not-withstanding the seven months' enforced

By F. J. C.inactivity from the record -breaking point ofview, her skill remains. She proposes toattack the few remaining records which donot stand to her credit as well as to en-deavour to beat her own 50 miles record.She is now acting as her own manager.

Materials for Bicycles

MANUFACTURERSare endeavouring

to export 75 per cent, of their output,thus leaving 25 percent. for home consump-tion. It is possible, however, now that mostof the factories are manufacturing muni-tions, that materials may not_ be availablewithin a short time for the manufacture ofcycles. As from June 10th, the prices ofbicycles were controlled by GovernmentOrder, and it is now illegal to sell bicyclesand accessories at prices higher than thosewhich obtained in August last, plus certainagreed war -time increases. Already manu-facturers are well behind with deliveries.

Identity CardsAREMINDER that cyclists should

always carry their identity cards.They are liable to be stopped, especially atnight, and it avoids complications if thecard can be produced at once. In this con-nectioh it must be remembered that thepolice now have powers to detain anyonefor inquiries for 24 hours.

Third -Party Insurance-Credit to.C.T.C.N last month's issue when referring to theI

retirement of Mr. H. N. Crowe, wereferred to the fact that one of the innova-tions for which he was chiefly responsiblewas the third -party insurance. We madethis statement in common with othercycling periodicals, intending to convey thatit was an innovation as far as the N.C.U.was concerned. They did not, of course,originate the scheme, for the C.T.C. severalyears before had introduced a scheme offree insurance for its members.

The Cumnock RallyY the time this appears in print the

B Cummock Rally will have been held.As we go to press we learn that a Dinnerwas held at the Hotel Royal on Sunday,June 30. The rally itself consisted of galaevents, community singing, races, treasurehunt, bicycle polo, and speeches. In spite ofthe war, excellent support was received forthe rally, which has done so much to fosterinterest in cycles and cycling.

Godwin Does It

TOMMYGOI)WIN, who, as mentioned

last month, demonstrated that his dailywanderings for over a year of '200 miles aday had not affected his speed, rode the lastlap of the 100,000 miles he set himself to do

All letters should be addressed to theEditor, "THE CYCLIST," George Newnes,Ltd., Tower House, Southampton Street,

Strand, London, W.C.2.'Phone : Temple Bar 4363.

Telegrams : Newnes, Rand, London.

in 500 days, at the Paddington Track onWhit Monday. Owing to the cancellationof the meeting of which this last lap was tobe an event, he restaged his last lap rideon the following Saturday. He actuallycompleted his 100,000 miles in 499 days.

The Parachute Patrol CorpsOVER two dozen police constables have

written to the N.C.U. in appreciationof their formation of the parachute patrolcorps.

Aliens and BicyclesUNDER a recent Order, aliens in this

country may not possess a bicycleunless they are in possession of a specialpolice permit. This new Order applies to allaliens over 16 years of age, whatever theirnationality, and it orders them to be intheir homes at 10.30 p.m. or by midnightin London. Apparently, the police are grant-ing permits to aliens who satisfy them thata bicycle is necessary in connection withtheir work.

Another JubileeTHE British Cycle & Motor Cycle Manu-

facturers & Traders' Union this yearcelebrates its Jubilee, for it was half acentury ago that a few bicycle manu-facturers, for their mutual protection,formed themfielves into the Cycle Manu-facturers' Trade Protection Association. Itwas some years later before its title waschanged. The B.C.M.C.M. & T.U., hasdone an enormous amount of work in theinterests of cyclists. They organisedNational Bicycle Week in 1923, and morerecently the Keep Fit publicity scheme, onwhich they spent £25,000. During itshistory they have organised no less than23 cycle exhibitions, and have given largesums of money to charity. They also wereresponsible for the formation ,of TheNational Committee on Cycling. Theyregard the interests of the users of bicyclesas more vital even than the interests ofmanufacturers, and they have acted inconjunction with the C.T.C. and theN.C.U. on many occasions.

The Century DecisionBECAUSE the Century Road Club

thinks that war conditions require itthey have cancelled their road events andbanned their members from competing inevents promoted by other clubs. No clubhas the power to prevent its membersentering 'opens" run under R.T.T.C. or-other recognised rules. It can, of course,prevent its riders from competing inunauthorised events, but the Century RoadClub in this case is, in our view, out oforder. We therefore advise any member ofthe Century Road Club, who wishes tocompete in opens to do so, in the knowledgethat his club has no power to prevent himdoing so.

Incidentally, the badge of the CenturyRead Club advertises a particular journal,which is contrary to R.T.T.C. rules. Per-haps the secretary of the R.T.T.C. willmake a note of this !

I0 THE CYCLIST July, 1940

An American VictoryWALTHOUR and B. Thomas scored

J a victory for America in the recentsix -day cycle race held at the DuquesneGardens, Pittsburg. They covered adistance of 2,366.7 miles. "Torchy" andDouglas Peden, the popular Canadianpair, were second.

A Bicycle BalletAN immense spectacle called "The American

Jubilee" is one of the features of the New. York,World's Fair for 1940. Included in the Jubilee is abicycle pageant in which 72 riders will appear on astage 300 ft. wide. The cyclists will do trick ridingand drill formations on ordinary stock bicycles andnot on specially built machines which are generallyused for trick cycling.

Spring SuspensionASPECIFICATION

has recently been publishedfor yet another spring suspension for the

fork -mounted wheels of pedal cycles.CC uid Pro Quo"

E manager of Currys Walthamstow branch,I Mr. A. Ford, was recently concerned in a little

roadside Incident. He wasreturning from a visit to acustomer in the depot vanwhen he came across acouple walking and push-ing a tandem. He pulledup and asked if he couldbe of any help and wastold that the unfortunatecyclists had burst a front

tyre, were 10 miles front home and had nomoney. Mr. Ford was able to effect atemporary repair which he learned after-wards saw the couple safely home; theycame along to thank him and to buy a newtyre to replace the damaged one.

ParachutistsMR. J. W. BRYAN, director of the

B.S.A. Company has made an appealto cyclists not to leave their machines wherethey can get into the hands of parachuteinvaders.

Death of Mr. T. SuttonTHE death occurred recently of Mr. T.

Sutton at the age of 65. When a youngman he was one of Fenland's foremost skatersand was equally well known on the cycleracing track. He was recognised as almostunbeatable in 2 to 5 mile races and hisracing opponents included such well knownold-timers as Callagan, Fred Hawes, S.Greenhall, Kemp, Greenwood, Bamber, Stan-ford and W. Horn.

Bicycles and Machine ToolsIN his presidential address to the Birming-I ham section of the Institution of Produc-tion Engineers at the James Watt Institute

ParagramsCurrent News Reviewed

recently, Mr. R. C. Fenton dealt with " Pro-gress in Machine Tool Design." He said thatthe general public does not fully realise how im-portant is the part played by machine toolsin our civilised life. The production of almost anyengineering product-as, for example, bicycles-isdependent entirely on the ingenuity and skill of themachine tool maker in devising the necessary machinetools for cheap production.

Cyclists and Cleethorpes SignalsOMPLAINT was made at a recent meeting ofC Cleethorpes Borough Council that the weight of

a cyclist Is insufficient to oporate the town's trafficlights and men are often late for work because theyhave to wait for the lights. One cycling alderman alsocomplained that the lights are almost invisiblein daylight and said hethought they were redone day when they act-ually were green.

Tommy Goodwin at the Paddington track setting off on his last lap to complete his record ride of 100,000miles. On the left is Charlie Davey and Mr. E. Coles -Webb is on the right.

NOTES OF AHIGHWAYMAN

By L. ELLISwANTAGE is a pleasant market town

in the Vale of the White Horse. It iscelebrated as the birthplace of King

Alfred in A.D. 849, but is singularly lackingin other historical connections. Alfred'sWell and Alfred's Bath can still be pointedout but it is to be feared that little or noth-ing remains in Wantage as a memorial toa great king. His palace is gone and notrace remains of the manor that followed it.The greatest monument to his memory arethe sites of his many battles with the Danesin the neighbourhood and it is said that thegreat battle of Assendun; or Ashdown,was fought on the chalk ridge near the town.Tradition goes on to say that the so-calledWhite Horse at Uffington commemoratesthe victory and that the carving wasexecuted by Alfred's orders. Most peopleare agreed . however that this particularwhite horse was old before Alfred was born.There is a fine statue to Alfred in the

't

The sundial and lock -up, Steeple Ashton, Wilts.

market place and the inscription is evenfiner and very much to the point. It reads :"Alfred the Great, The West Saxon King.born at Wantage A.D. 849. Alfred foundlearning dead, and he restored it, educationneglected and he revived it, the laws power-less and he gave them force, the churchdebased and he raised it, the land ravagedby a fearful enemy from which he deliveredit. Alfred's name will live as long as man-kind shall respect the past." In the marketsquare there is a picture gallery known asthe Victoria Cross Gallery.ONCE A CELEBRATED' MARKET

THE village of Steeple Ashton, four milesfrom Trowbridge, gets its first name from

the staple, or market, that once was heldthere. Market rights were granted bycharter in 1387. An old market cross oncestood in the middle of the street and it issaid that its erection coincided with thedate of the landing of William, the Con-queror. The spot is marked to -day by a tallsundial, erected about two hundred yearsago. Quite near it is a curious old round,or nearly round, house, once used as avillage lock -up. Steeple Ashton wasfamous until the sixteenth century as theheadquarters of a colony of cloth manu-facturers and many memorials to theirgenerosity may be found in the interestingchurch.

July, 1940 THE CYCLIST I

Those Folding Bicycles

THE daily newspapers with that propen-I sity for perverting facts for which they

are renowned have been making a good dealof the alleged use of folding bicycles byGerman parachutists. The amount ofequipment which these parachutists arealleged to carry would break somethingmore than a camel's back. Our experts of thedaily press would be better occupied asimaginative fiction writers, for the facts arethat the parachutists' equipment is droppedin a separate container after their descent. Acertain section of the press imagines thatevery ingenious device must necessarily beinvented by a German. They have acomparatively short memory for Britishinventions, even if they have never heard ofthem. Folding bicycles were first producedin this country, and over 50 years ago.They were used to a small extent in theSouth African war, and to a somewhatgreater extent by the Allies in the last war.Within the last five years the New HudsonCompany produced the bolted -up bicycle,which could be quickly dismantled andpacked into a case no larger than that re-quired to pack two wheels.

In America the Westfield ManufacturingCompany, who make the Columbia bicycles,have produced the folding bicycle illus-trated. According to their claim it isAmerica's first folding bicycle. Creditwhere it is due.

AROUND

THE

WHEELWORLD

By Icarus

A MonthlyCommentary

Electrically -Operated Bells

MIN

I N conversation with a friend in the traderecently, he suggested that as a goodly

proportion of modern bicyles are equippedwith a lighting dynamo the current could beused to operate the bell. On the face of it,this seems a practicable arrangement untilwe remember that the dynamo is only putinto operation after lighting-up time, andeasy running as most modern dynamos are,cyclists would not consent to trundle themround all day in order to provide theoccasional electrical energy required tooperate the bell. The scheme would work,of course. It would merely be necessary toincorporate on the stator plate of the bell asimple vibrator or trembler coil similar toan electric door bell. In view, however, ofthe comparatively small current outputand the fact that most dynamos generatealternating current, there are other com-plications which put the idea out ofcount.

Magnetic Spokes'

WHICHreminds me, that some time

ago I took out a patent for obtaininglight through the medium of magnetisedspokes. Such a scheme would mean a con-siderable saving in weight. A test showedthat it worked. It was, of course, particu-larly necessary to see that the north andsouth poles of each magnetised spokewere at the correct ends of the spokes. The

coils were arranged around each limb of thefront fork, but even so it was not foundthat a sufficiently brilliant light could beobtained, apart from other disadvantages.

The Course -Limit FactorMOST handicappers are cursed by the

handicapped. It is their problem toreduce a time trial by a process of arith-metic to an arrangement whereby each riderwould finish in the same time. It neverworks out that way. A handicapper mustessentially handicap on the riders' previousknown time for the particular distance. Sucha time may have been made on a good courseor a bad one, and it is impossible for anyhandicapper to take an accurate account ofthat. Also, the time might have been madeon a bad day when rain and/or a head wind

-or a following wind affected the time of theride. The good handicapper will alwaysallow a little for improvement on the partof the rider since his previous time wasmade. It seems to me that what is wantedis a course's limit factor which should betaken into account as well as the time.

Alec Horwood Escapes

ALEC HORWOOD, previously captainof the Bath Road Club, and still a

Member of it was. I learn, made a prisonerof war but he escaped and is now in thiscountry. Which reminds me that someconsideration should now be given to theform of memorial for cyclists who fall in thepresent war. The Cyclists' Memorial atMeriden was erected to the memory ofthose who fell in the last. Obviously,something similar will be done when thispresent holocaust is over and we have givenHitler his quietus; but now is the timeto think about it.

Useful Hand book

THE Farmhouse and Country HolidayHandbook for 1940-41 makes its appear-

ance at 7fd. It is published by the Farm-house Holiday Bureau, Salterns, Eashing,near Godalming, Surrey. This handbookmakes the search for accommodation easy.It lists 350 farms and country houses insome of the most delightful parts of thecountry where holidaymakers will bewelcomed and provided with comfortablerooms and good home-grown food.

The Poor TimekeepersEVERYONE knows that time trials arc

run for the benefit of timekeepers. Theabandonment of many events does not, weunderstand, meet with their approval !

The Columbia folding bicycle referred to by Icarus.It is of .4merican pattern

12 THE CYCLIST July, 1940

IWANT to make the readers of thesenotes feel that a cyclist is talking tothem who has had practical experience

of the road and the vehicle on which he hascovered some 400,000 miles of our Britishand Irish highways in the last 51 years.Naturally, all of us have our own ideas asto the best method of using a bicycle so thatwe shall obtain from it the greatest value,either in ease of running or speed of travel,and longevity of service combined withreliability.

I came into the cyclist movement juston the threshold of the arrival of thepneumatic tyre. As a matter of fact, thatarticle had not been marketed when I wasgiven my first bicycle by an indulgentparent. Since those days, at the tender ageof ten, I do not think I have been divorcedfrom the saddle of a bicycle for a wholefortnight, and during those fifty years havebestridden every type of bicycle andtricycle marketed since 1890. Many ofthem are now completely forgotten, andsome of them were impossible freaks.Present -Day Conditions

After all these years, it is natural thatI should have settled down to a type ofmachine that suits present-day conditionsand my own particular notions of what abicycle should be for comfort. The ques-tion of speed, as such, has long ago departed,and the translation of momentum, as far asI am now concerned, is purely a questionof how easily I can cover the miles andgather an enjoyment of road roaming thatseems to become greater and greater as theyears roll by.

I do not intend, with the Editor's per-mission, to paraphrase the many and variousbooks that have been written on the upkeepof a bicycle, or the best methods for theindividual use of it ; but rather to deal withthe matters concerning cycling as they occurto me without tabulating their form orinsisting that my point of view is the rightone. Quite obviously there is a widedifference between people of a like mindin the matter of the convenience and thelove of cycling, and the best methods wishwhich to implement cycling's means oflocomotion.

I imagine that I have been fairly catholicin my ideas, and all my bicycles, while ofvery similar specification, are variouslyequipped except as regards those mattersof comfort which to me are paramount inbicycle specification if happiness a wheel isto be attained and fully exploited.Comfort Awheel

I have said on numerous occasions, andI make the statement again here, thatunless an individual is comfortably seatedawhee' it is impossible to enjoy cycling,

WAYSIDE THOUGHTSBy F. J. URRY

Hints on Choosing a Bicyclehether it is undertaken as a pastime or a

mere matter of convenience. Therefore, itfollows that I consider the most importantpart of the equipment of a bicycle is thesaddle, for if you cannot' sit comfortablyand at ease under all conditions, then thehandicap on enjoyment is a very serious one.Time and again 1 have tried most of themakes of saddle now on the market, andmy own choice is for a leather saddle whichis wide enough to sit on, long enough toshuffle on, and light enough not to beburdensome.

I have a leather saddle in service to -daythat has been unchanged for over eighteenyears, and the name stamped on the flapof the saddle has been entirely obliteratedby the friction of the garment that comes inclose contact therewith.

That, I think, is the first thing any cyclist,or would-be cyclist, should bear in mind.Unless you are comfortably seated, it isimpossible to enjoy cycling, just as it isimpossible to enjoy walking unless you arecomfortably shod. It is an astonishing thinghow many times in my life I have discoveredindividuals endeavouring to use themselves

Liqh1-1LA SprungSaddle

LonStaa

Orthodox3 -Speed

Smooth. StrongBrakes

Good StrongFrame

6'/;Cranks

Lovv BottomBracket -

14 -42 approximately

for colourful finishes, and 1 can quite under-stand that the younger generation find theseentrancing, particularly when the bicycleis in its pristine condition ; but if you wanta machine to last and look well at the endof several winters' hard work, then there isnothing to beat an all -black finish of rubberenamel without any shiny coat as generallygiven to the all -black bicycle.

A Lasting InvestmentIndeed, I have a machine now in regular

use which only takes the road when theweather is inclement because it is fitted witha perfect oil -bath case, and that machine is22 years old, yet it could be taken as amodern example of perfect cycle engineeringafter it has had a sponge down. It is truethat the only original parts of the bicycleleft are the frame, cranks, chain (which haslasted all those years in its oil -bath case),handlebars, saddle, and hubs. The pedalshave been replaced, the brakes have beenreplaced, the rims have been replaced, andI do not know how many pairs of tyres thatmachine has worn out. but it must run toat least something between six and ten.

Handlebar Width/16approximahelt.i

71'cipproximol-ely

Points to consider when purchasing a new machine

to the wrong type of saddle for their purpose,and always finding the process uncomfort-able ; whereas a change of saddle has workedmiracles to their wheeling happiness.

The Bicycle ItselfWhen this question of saddle has been

satisfactorily settled (and, believe me, it isnot an easy matter to bring home to theaverage rider the importance of the saddleand its relation to happy cycling), then thenext thing to consider is the bicycle itself.This should be as small as possible, and itsdetails of the simplest nature.

When I say the bicycle should be small,I mean that the need for high frames inthese days has entirely' departed. Eventhe tallest man should not need more thana 24 in. frame, since the leg length can beobtained by a long saddle pillar andhandlebar stein.

It is obvious that the smaller the bicycleframe, within reason, the more rigid it mustbe as well as lighter, and those are the twomain items in the construction of a goodclass, easy -running machine-rigidity andlightness.

I am aware that the modern tendency is

26"Wheels

I merely mention that bicycle to showthat a really good -class bicycle, finished inall rubber black enamel, is a lasting invest-ment, and far cheaper in the long run thana machine at a third the cost, as well asbeing much more reliable.

People must, of course, please themselvesin regard to finishes. Generally they areoptional, or at least there are many typesof finishes which most of the manufacturerscan supply, sometimes at the list figurequoted, but frequently at a small extra forspecial colours. These machines, I admit,make a gay procession along the road, butsometimes I have seen them when neglecthas given them almost a discarded air, andmade them appear but a sorry shadow oftheir younger days. That never happens inquite the same degree, to the all -blackfinish, however neglected that machinemay be.

The other important items of equipmentare wheel size, which are now mostly 26 in.,for the sake of obtaining a low bracketposition, whereby the rider can alwaysdrop his foot to the ground for the purposeof easily obeying traffic or police signals.

( To be continued)

FHE CYCLIST 13July, 1940

Yourenjoymentdependson goodTYRES

CHOOSE FROM THE FIRESTONE RANGE

Sports Made in either red or black, theFirestone Sports tyre is scien-

tifically designed for fast riding with extrasafety. Its light weight is achieved by extrafine quality-ensuring flexibility and livelinessvet setting a new standard of strength in Sportstyres. Sizes 26 x Fr. 26 x 12. Cover 71., Tube 2'9.

Oldfield This rugged tyre has the feature,of t he Oldfield Car Tyre renowned

for its substanti.,1 saving in first cost yet givingwonderful mileage and safety. Sizes 28 x26 x 26 x H. 26 x If. Cover 5;-, Tube 2'-.

Sentinel High quality at a wonderfullylow price ! Amazing value only

possible through the experience and skill ofFirestone Tyre Engineers, combined with thefacilities of the World's n ost Modern TyreFactory Sizes 28 x If and 26 x If. Black only.26 a If and 26 a Il. Red or Black. Cover 3,9,rube 1/9.

Tandem With a deep tread of theFirestone Sports Tyre design

and cord fabric specially impregnated withextra rubber the Firestone 26 x It6 Tandemtyre has extra strength and liveliness perfectlybalanced. It is the most modern tyre everdesigned for the Tandem rider, yet it is offeredat a popular price. Cover 7 -, Tube 3,-.

Roadster ,?fe'ai"8exri ri teh thee Ffi=esRoadster sets a new standard of values in CycleTyres. The rugged tread gives greater safetyand mileage. Underneath are cords of the finestquality giving extra strength and extra flexibility.Sizes 28 x . 26 x 11 26 x IL Cover 8 3, Tube 3 -.

4rtttetitMADE IN ENGLAND

Firestone Tyre and Rubber Co. Ltd., Great West Road, Brentford, Middx.

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Britain's Cycle SfreciakisNENRLY Orates/

For Brimin's Best service comeCO Currys! At over 230 branchesthere are Currys experts alwaysready to ensure that you get theutmost value for your money.

Ask at your local Branch for NEWCatalogue FREE-or send a post-card to:-Currys, Ltd., Head Office, GreatWest Road, Brentford, Middlesex


(ME OWNERS ARE LUCKY!They have the essential means oftranslort

for business and pleasure... AND, they eau* a

*In the Club Model shownabove there is a shock -absorbinghinge which takes up road jarand vibration, acts as an extra

cushion'. and prevents fatiguebreaks in the frame.

*There's a screw in the nose of the Saddle. Twistit with a coin, and the seat springs relax or growtaut to suit YOU!

TERRYADJUSTABLE -SPRING SEAT SADDLE* comfort

Cycle owners possess the easiest and cheapest means ofgetting about. They have the freedom of the roads-without tax or restriction. Best of all they can havetheir machine fitted with a TERRY Adjustable SpringSeat Saddle. The TERRY Saddle protects the rider fromspine -jarring bumps and jolts. It abolishes saddle -soreness. It needs no "breaking -in." It is the ONLYSaddle that can be instantly and accurately tensionedto suit the exact weight and riding need of any individual.

TERRY Adjustable Spring Seat Saddles are equipped withweatherproof REXINE COVERS, amazingly durable . . .

BRY-FELT LINING (the perfect cushioning) and TERRYSPRINGS, which keep their strength and elasticity for alifetime.

Club Model I2/- Roadster Model 15/6

Herbert Terry & Sons, Ltd., Redditch, Eng.

FAMOUS

FOR SPRINGS

& PRESSWORK

SINCE

1855

Why"CANTILEVERS

CANTILEVERSCost 12/- each, front or rear.

In nickel or enamel finish.Chromium plated ... 14/ -

TANDEMCANTILEVERS

are I3/- each, front or rearIn chrome ... 15/-

53are the finestbrakes on earth

We say in our advertisements that " CANTILEVERS " are the finest brakeson earth. It is no idle boast-we can prove it. They are light butexceedingly efficient, the working parts are anchored where the force isexerted. Road tests, carried out in the presence of many of the leadingfigures in the cycling world, proved that an I I.', stone rider travelling at16 m.p.h. down a steep slope could be brought to a standstill in 20 yardswith a 6-1b. pressure on one "CANTILEVER." Other brakes tested atthe same time required 334 yards. The " Cantilever " blends perfectlywith the lines of a bicycle-it is not " stuck on " like an ugly excrescence.It is capable of micrometer adjustment. The slightest pressure on the leverbrings the machine to a standstill swiftly, smoothly and safely.

Let us send you an illustrated cataloguedescribing the world's best cycle brakes.

THE RESILION CO., LTD.,Phone: North 1351. T'grams: Nordo, London. 200 Liverpool Road, LONDON, N.I

July, I 94C THE CYCLIST 15

MANY and various are the differentvarieties now on the market. Theycan, however, be classed under two

main heads, viz. hub -gears and derailleurs.The first are totally enclosed in the rear huband obtain their results by means of pinionsoperating on the "sun and planet prin-ciple. The latter, as its French nameimplies, gains its gear changes by derailingthe chain and causing it to jump from onecog to another of different size.

Hub GearsUntil quite recently, the main arguments

against hub -gears were that the differencesbetween their various gear sizes were toowide and that it was necessary to backpedal slightly in order to cause them tochange. These two disadvantages havenow been completely removed. Though thewide -ratio hubs with their 33A per -cent.jump upwards and their 25 per -cent. dropdown from normal are still available, therealso are models which provide 15 per -cent.and 7 per -cent. alterations respectively.The wide ratio is intended for tourists whowish to tackle all varieties of gradient;riders, that is, who prefer ease to mere speed.The medium ratio hub is designed for theclub rider, those who at times travel fastover undulating roads, those, that is, whowant comparatively slight changes of gear -size and are prepared to pay the price for itin harder pushing on the upgrades. Theultra -close hub with its mere 7 per -cent.change is meant almost exclusively for useby the racing man in time -trials over roadspicked for their easy gradients. He requiresonly almost imperceptible, changes. Toalter his gear more than a few inches at atime would completely destroy the rhythmof his riding, vhile to drop his gear too lowwould give his opponents an unnecessaryadvantage. Used by itself this model is notof much practical use to the tourist-thedifference between the top and the bottomgears being far too small to make muchdifference in one's ability to climb the steephills invariably found in " real " touringcountry. Used in conjunction with adouble chainwheel and a chain -shiftingdevice, however, I have been able to obtainsix gears which were so delightfully closetogether that I was not conscious of anyalteration in pedalling rhythm or pressurerequired whenever it was necessary for meto change, yet, nevertheless, giving me awide enough change between top and bot-tom to meet all gradients.

Massed -Start RacesThe massed -start rider races, as a rule,

over far hillier courses than the time-trialist, and hence requires a much lowerbottom gear while still requiring the highones. The needs of the average fast club -rider who must be always ready to counterthe speed -moods and spasms of his clubmates are very similar. For such as these,the 4 -speed hub -gear has been designed.It is made in two types, the close ratio andthe medium ratio. The former gives a high

Gears andGearing

By A. W. BRUMELL

Continued From Page 7 ofLast Month's Issue

gear with a 9.1 per -cent. increase fromnormal, a normal gear taking the directdrive, an intermediate gear giving a 10per -cent. decrease from normal and a low -gear giving a 25 per -cent. decrease fromnormal. The medium ratio model gives a12.5 per -cent. increase for the high and14.3 per -cent. and 33.3 per -cent. decreasesrespectively for the two low gears. Per-haps it will convey more if I quote definitegear sizes to illustrate the possibilities of thehub. With the close ratio, using a 44 -toothed chainwheel, a 14 cog and a 26 -in.wheel, one can get gears of 61.3, 73.5, 81 7and 89.2-a very useful set indeed for themassed -start racing -man. Replace theeasily removed, splined 14 cog by a 16toothed one and the very useful combina-tion for mixed touring and club -riding of53.6, 64.3, 71.5 and 78.1 is obtained. Fora rider more interested in touring themedium ratio type used with the sameequipment and a 17 cog will offer gears of45.2. 57.7, 67.3 and 75.7.

Two -Speed Hub Gears.There are also 2 -speed hub -gears. These

are also in two ratios designed so to coverthe needs of both the racing man and thetourist. For the former, the close ratiogives a low gear with a 13.46 per -cent.reduction from the direct -drive normal.This reduction is equivalent roughly to atwo -teeth increase in the number of teethon the rear cog. In other words, a time -trialrider could have a 77 gear for going outinto the wind and an 89 for coming backwith it. Added to this, by using either afree wheel or a fixed cog on the splinedhub, he could use either a free or a fixedgear-a choice not open to him on any othertype of change -speed gear. The snag is,of course, that very few courses are straightout and home into the wind and one mighteasily discover that a cross wind would findone without a gear to suit the occasion.Twelve inches is too big a difference ninetimes out of ten and most riders wouldprefer the little extra weight of a three -speedjust for the sake of the handy middle -gear.

The wider ratio two -speed gives a lowgear with a reduction of 25 per -cent. fromnormal, a difference, equivalent roughly toan increase of four teeth on the rear cog.Having used such a gear fitted with gearsof 73.5 and 55.2 for several years beforethe three -speeds were improved to theirpresent efficiency, I can vouch for its slickchanging and useful performance. Nowa-days, however, I require a wider selectionboth in number and size. Seventy-three isnot high enough with a gale behind nor55 small enough for a " 1 in 5 " hill Themuch -vaunted " fixed or free " advantageis all very well for the racing man endeavour-ing to get fit and bent on using as muchenergy as possible in the shortest possiblespace of time.

(To be continued)

Classified AdvertisementsRATES.-Twelve words 2s. (minimum). 2d. perword after. Each paragraph charged separately.

NEW CYCLESLIOBBS OF BARBICAN. manufacturem of modert11 frames, cycles, tandems and tricycles. Specielists in frame design. Lists and individual quota-tions free. Personal attention to every order. -34Barbican, London, E.C.1.

GROSE SPUR All British Cycles, 75s. Art List 100models free.-Grose, Ludgate Circus. London.

BAWES Super Responsive Cycles. Ultra shortW/Base, or standard design models. New

catalogue free. --Idle Road, Bradford, Yorlis.

ACCESSORIESGEORGE GROSE, the best -house for all cycle

accessories. Write for beautiful art illustratedlist, post free, 3d.-Ludgate Circus, London.

CAMPING EQUIPMENT("NAMOT_7FIAGE your tent by brushing onV Granger's Solution Camobrown and Camogreen.which will waterproof and preserve it withoutstiffening. ls. 9d., 3s., 5s. Exi.; 1 gallon, 10s. 6d.,treats 240 square feet of 6 oz. canvas. From Scout(and Guide shops, camping outfitters. HAfords andstores.

CLEARANCE SALE4 USTIN'S, main distributing agents for Raleighs.

B.S. A., Sown, Dayton, Rudge, Aberdale,Saxons, Sunbeams, Royal Enfield and Hercules.Large prices given for your machine in exchange,Ladies' second-hand cycles wanted.-Austin's.147-153, High Street. Harlesden, N.W.10. Willes-den 2099.

CYCLES WANTED-VI ORRIS pays top prices for old cycles, -ladies' andI gents'. Cash waiting at door. Any condition.-Morris. 89, Tottenham Court Road (middle).(Museum 4910.)

GEARSDERCY FREEMAN, Specialist in Derailleur gildI Hub Gears; also B.S.A., Raleigh, Sun, Dawes,Rudge and Gazelle in stock. -109., Brownhill Road.Catford, S.E.6. (Hither Green 2779.)

INSURANCEASR your dealer for one of our Insurance Certifi-

cater; or write direct Vehicle and General In-surance Co., Ltd., Royal Liver Buildings, Liverpool.

LADIES' AND GENT'S CYCLESATORRIS for used, secondhand and shop-soiled11'1 bargains from 30s. Big range. good makes.Deposit secures. Agents all makes.-Morris, 89.Tottenham Court Road (middle.

PERSONALYCLIST-MOTORIST. 35, single, desires young.

ll cheerful companions week -ends; Kingston -onThames.-Box 466, PRACTICAL MECHANICS.

TYRESNEW TYRES. Clearance, best makes,

1_09000 331% off standard prices. Carriagepaid. Price List on application.-Davies, TyreFactory, Wednesbury.

MISCELLANEOUSITOU need a War Atlas when you read the news -1 papers, or hear Wireless bulletinfl. "Newnez

Comprehensive War Atlas" will make the progressof the conflict fully understandable.-Of all book-sellers, ls. 6d., or by- post ls. 9d. from GeorgeNewnes, Ltd. (Book Dept.) Tower House, Southamp-ton Street, Strand, London, W.C.2.IN peace and war the work of to rchant ships isI vitally important. "Ships at Work," by A. C.Hardy, takes you aboard every type of vessel,and shows how they do their work.-Of ail...book-sellers. 7s. 6d., or by post 8s. from George Newnes.Ltd. (Book Dept.), Tower House, SouthamptonStreet, Strand, London, W.C.2.A RE you a house -owner ?-In "The House -Owner's

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THE CYCLOMETERMANUFACTURERS

Standard Model - 211 eachDe Luxe Model - 3 6 eachTo Fit 24". 26" or,e28" Wheels.

H. J. Thormann Engineering Co. Ltd.

PERREN STREET, LONDON, N.W.S.

hrl,111:1,1Plated

BRITISHMADE


Did They Tell William The ConquerorWhere To Go ?It is presumed that-although no historical evidence is available-serfs and vassals told William to go to .... Normandy.

But strangely enough-nobody can tell Williams-the Conquerorsof Transmission Troubles-where to go, because all over the World

you find " the Williams Set "already well established.So-apart from the alternativeadvice offered by senile pedes-trians and impatient motoriststo cyclists, the latter know quitewell " where to go "-morespeedily and with less effort-onWILLIAMS.

STNFro n gueror,s. OF

TRANSMISSION TROUBLES

EDWARD WILLIAMS, FOUNDRY LANE, BIRMINGHAM

TUBA

Regd. DesignNo. 828997.

Prices maintained.INDIVIDUALLYGUARANTEED.

ForCycle Dynamo

Outfits.INSTANTANEOUS LIGHT AT WALKING SPEED when, with theusual Bulb, there is no light. POWERFUL LIGHT immediately in front,stretching far ahead and illuminating both sides of the road. GREATERVOLTAGE OUTPUT-over 13 Volts from 3 Watt Dynamos at 15 m.p.h.-as certified by the N.P.L. SOUNDER CONSTRUCTION due to allFilaments now being Centre Supported. LONGER LIFE, becausewith 'TUBA' there is 30 per cent. more space within the actual balloon,enabling the more easy cooling of the Filament and the, absorption ofthe gases emitted therefrom.BAYONET CAPPED BULBS (i.e. push -in) For LUCAS, MILLER, &c.

'TubaRef. Balloon

Description. No. Frostedor Clear.

Price.

For use with 6V 3W LSC Clear 1/ -Dynamo Outfits LSF Frosted 1/11

For use with 1.8W L9C Clear 1/ -Dynamo Outfits L9F Frosted 1/11

For use with 6V 6W M9C Clear 1 /-Dynamo Outfits I M9F Frosted 1/11

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M.E.S. CAPPED (i.e. screw -in) FOR BEMO, STARLIGHT, LUCIFER, &c.

For use with 6V .3A 852 Clear 8d.Dynamo Outfits 851 Frosted 9d.

Specially for BEMO 862 Clear 8d.861 Frosted 9d.

For use with 6V. 5A 872 Clear 8d.Dynamo Outfits 871 Frosted 9d. Ref. 871

THE WHOLE OF THE ABOVE BULBS HAVE BEENMANUFACTURED FOR THE VITA 6V .04A REAR BULBSTO BE USED IN CIRCUIT THEREWITH. PRICE 7icl.

Send for Price List. Individual Bulbs Supplied. No Charge for Postage -VITALITY BULBS, LTD., NEVILLE HOUSE, NEVILLE PLACE,

WOOD GREEN, LONDON, N.22.

'first 1,1time

lass

BRAKEBLOCKS/are/ LINER %

liaols kW"'Remx

It's a wise cyclist whohas his brakes fittedwith Fibrax BrakeBlocks. They never failto grip in any situation-a sudden stop, a slowdown in dense traffic, asafeguard on a hill-it'sall the same to Fibrax.Economical, too, theywill far outlast anyordinary block. What-ever your make of machine,there's a Fibrax Brake Blockto fit it. Ask your dealer.

FIBRAX LTD., 2, Tudor Street, London, E.C.4

Ideal Book For Every Cycle - Camperspoil your trip by choosing the wrong camp -site, having trouble with your tent, eating smoky food,falling into the traps that beset the inexperienced camper. A perfect camp is assured if you read

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Available from all Booksellers 2/6, or by post 2/9 from the PublishersNEWNES LTD. (Book Dept.) TOWER HOUSE, SOUTHAMPTON STREET, LONDON, W.C.2.

19.44°

BUY, EXCHANGE OR SELLAavertisements are accepted for these columns at 3d. per word (minimum 12 words at 3s. -advertisements of less than 12 words arecharged at the minimum rate of 3s.) subject to a discount of 21. % for 6 consecutive monthly insertions or 5% for 12 consecutive monthlyinsertions. TERMS :-Cash with order. Cheques, Postal Orders, etc., should be made payable to George Newnes, Ltd. The Proprietorsreserve the right to refuse or withdraw advertisements at their discretion. All advertisements must be received on or before the 5th of themonth preceding date of publication and should be addressed to the Advertisement Manager, " Practical Mechanics," George Newnes

Ltd., Tower House, Southampton Street, Strand, W.C.2.

LITERATURE160 PAGES ILLUSTRATED REVISED WORK-

SHOP HINTS and Calculations in Calvert's Mechanics'Handbook, 8d., post free.-Sherratt & Hughes,St. Ann Press, Park Road, Timperley, Ches.

MISCELLANEOUSWANTED FOR PROMPT CASH. Miniature

Cameras, Enlargers and Accessories, Cine Cameras,... Proje,..',rs and Films. Microscopes, Telescopes and

Binocula Small Lathes and Precision Tools. -Frank's C a.nera Exchange, 67 Saltmarket, Glasgoyv.

TELESCOPES, MICROSCOPES, ScientificInstruments, etc. Send for lists. Sale or Exchange. -C. V. Bolton, F.S.M.C., 49a Leigh Road, Leigh, Lancs

MERCURIC INTERRUPTOR for RuhmkorffCoil. Electric motor alone cost 45/-. E1.-2 UptonGardens, Kenton.

JUBILEEWORM DRIVEHOSE CLIPSThe long -life clip with

the ever -tight grip

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011am.111RNETT Co. (CHEMICALS) LIMITEDGREAT WEST ROAD Isttw6riyortOnIEW.

FOTLESBOOKSELLERS TO THE WORLDNew and secondhand books on all technical subjects113-125 CHARING CROSS RD., LONDON, W.C.2

Telephone: Gerrard 5660 (16 lines)411

OUR ADVICE BUREAU

COUPONThis coupon is available until July 31st, 1940,and must be attached to all letters containingqueries, together with 3 penny stamps. A stamped

addressed envelope must also be enclosed.PRACTICAL MECHANICS, JULY, 1940.

MODEL AIRCRAFTWOLVERHAMPTON. -Wolverhampton's aero-

modellers' rendezvous. START and SONS, 61 VictoriaStreet. Kits by all the popular makers, petrol engines,etc., selected balsa wood, spruce, cements, dopes,rubber, etc., and the most complete range of materialsand accessories.

PHOTOGRAPHYPHOTOGRAPHIC MATERIALS. Plates, films,

mounts, chemicals. Interesting money -saving listsfree.-"Kimber's," 105 Queens Road, Brighton.

PATENTS AND INVENTIONSIF YOU have an invention write for particulars of

my service.-B/M. Grail, London, W.C.1.

TOOLSGRAYSON'S Glass -boring Outfits and Tube

Cutters avoid risk. -Below.DRILLS, Taps, Dies, Files, Chisels and Punches

Best quality at keenest prices. -Grayson & Company300 Campo Lane, Sheffield.

BRAND NEW POWER TOOLS of quality10 -inch bandsaws, 54s.; Jigsaws, 22s. 6d.; BenclDrills, lls.; Circular Saws from 25s.; 3 -inch S.0Poolroom Lathes, from £4 5s. New 1 -inch chromiumplated Micrometers, 12s. 6d.; Electric Drills, 37s. 6d.Grinders. -John P. Steel, Bingley.

Independent Lathe Chucks, 4", 5", 6" diam.; completesets of parts, require very little machining; screwsdirect to mandrel, no back -plate required; completewith Four Steel Jaws but without Key, grandbargain; 4", 3/9; 5", 5/-; 6", 6/- per Set. Burke.

Machine Vices, 21" Jaws, 1" Deep, opens 31"; completesets of parts, only require drilling and tapping,3/9 set. Burke.

400 Genuine Carborundum Wheels, 11" Wide, 1" Hole,5" Diam., 1/9; 51" to 6", 2/6; 61" to 7", 3/6. Burke.

2,000 Small High-speed Twist Drills, .020" to .065", 2/ -per Doz. Burke.

2 Tons Steel Blanks, 21" to 5" Diam., 1" to i" Thick;Doz. assorted, 4/9. Burke.

3/- any Lot. SEVEN LOTS 81Approx. 200 Ass. Springs, to 4" Long.Doz. Ass. Whit. & B.A. Taps, to i" Diam. R.H.20 Ass. Ditto, Left-hand, to g" Diam.3" Sq. Toolholder with Four H.S. Tools.Eight Assorted H.S. Tools for Above.-i1.6" to A" Silver Steel, 13 pieces, 13" long,

ground to size.i" to i" Silver Steel, 4 lbs., 2" to 4" Long.1" to 1l" Silver Steel, 6 lbs., IA" to 3" Long.116" to A" Super High-speed Steel, Precision -ground,

6' Ass., 2" to 3" Long.500 Ass. Brass and Steel -plated Screws, etc.; B.A. &

Fine Threads, A" to i".100 Bright Hex. Bolts with Nuts, i" to 3" Diam., 1" to 3"

Long. Surprising Value.12 Ass. Fine Thread Taps, r to t" Diam.Three Doz. Tungsten Hack -saw Blades, any size, 9";

10"; 12".18 Grinding Wheels. 1" to 1" Diam., suitable for

Flexible Shaft use.Three H.S. Tap or Reamer Fluting Cutters, 11" Diam.,

3" Hole. Worth 6/- each.15 ass. Files, 4" to 6". Handy variety.12 ass. Files, 4" to 12".12 ass. Toolmakers' Needle Files. Indispensable.12 ass. Carborundum and Fine Emery Wheels, 1" to

-3" Thick:, 2" to 4" Diam., all 3" Hole.3 lbs. Best Blue Twill Emery Cloth Strips, i" to 2"

Wide; ass. Superfine to Coarse.81 orders Carr. Paid except abroad.

J. BURKE, 30, TRIPPET LANE, SHEFFIELD, 1.

Precision'

SITUATIONS VACANTAERO AND ENGINEERING INSPECTORS,

VIEWERS, etc. Work of National Importance andReserved Occupations for men over 21. For FREEGUIDE to rapid preparation and Employment Servicefor these vacancies, apply National Institute ofEngineering (Dept. 372), 148 Holborn, E.C.1.

WATCHMAKINGWATCH & CLOCK REPAIRERS. Send 6d. for

complete list of material and tools.-Blakiston & Co.,Ainsdale, Southport.

MUSICAL INSTRUMENTSBAND GUIDE. Hints on the Bugle, Drum, Flute,

Staff Parade formation, etc. Free, post paid. -Potter's (Manufacturers), West Street, London, W.C.2.

CHEMISTRY EXPERIMENTSIN YOUR OWN LABORATORY

elb osiFre:OFiER otSAMPLE PARCELcontaining manyuseful nie-es of

CHEMICALAPPARATUS

- 2/9Write also for

FREE PRICE LISTof other Sets.

BECK(Scientific Dept. A), 60, High St.,Stoke Newington, London, N.16.

Booklet, "Experiments in Chemistry," 6d. P.O.

MASTER THE PIANOEasily, Quickly, EnjoyablyTo learn to play really beautifully isnot difficult -it Is easy -with properleaching! Even if you start at middleage, not knowing a note. I CANTEACH YOU to play so that your

friends will want you always. I willsend you by POST, Sun -clear, FascinatingLessons using ordinary musical notation,

4't no freakish methods, enabling you toread and play at sight any standard musi-/' cal composition. I have enrolled morethan 1,500 adult pupils during the war.have taught over 51,000 during 35 years,and I CAN TEACH YOU, and I guarantee

, to please and even surprise you with yourA rapid progress. Send for FREE BOOK and

form for Free advice.Say if Moderate, Elemen-

t!./ 2;' tary or Beginner.

/ Mr. H. BECKERAt (British by Birth

and Descent).(Dept. 758), 69, Fleet Street, E.C.4 .

Price

£3-7-6

MachineVice 12: -

The 'ADEPT' Bench Hand ShaperLength of stroke of ram, 31 ins. ; Length ofcross travel of slide, 3 ins.; Size of Table,41 ins. -4 ins.; Rise and fall of Table,2 ins.; Vertical feed of tool slide, It ins.;Maximum distance between tool and table,3 ins.; Weight, 18 lbs. Also the 'Adept'

No. 2B.H. Shaper, 8i -in. stroke.Price 26-19-0.

Manufactured byF. W. PORTASS

si' TUERS STREET, SHEFFIELD.

Easily made from ourcastings

From12/6 Per Set

J. HALLAM & SONUpton, Poole,

Dorset.MINIATURE PEIROL ENGINES . . for

Aeroplanes and Speed Bosts. 1 to 60 e.c.Send 4/. for particulars.

All applications respecting Advertising in this Publication should be addressed to the ADVERTISEMENT MANAGER,GEORGE NEWNES LTD.,Tower House, Southampton Street, Strand, London, W.C.2. Telephone : Temple Bar 4303

o tV

Sunnis/ MISTHE VALUE GAMAG S

Send for copies ofGamages ToolBargain Leafletsfor Metalworkersand Woodworkers

Carriage (outside our e

61 SHEFFIELD MADEFOR TOOLS

9716I

Contains an exceptionally comprehensive range of fine quality tools-suitable for practically allwoodworking jobs. Chest stained and polished Walnut colour. Size: 27 in. by 11 in. by 7/ in.Fitted with fixed compartments for small articles, and movable tray with 24 spring clips to holdchisels, bits, etc. Contents: 1 Skew -back Handsaw, 22 in.; 1 Tenon Saw, 12 tn.; 1 Set 3 BladeCompass Saws; 1 Pad Saw and Handle; 1 Smoothing Plane; 2 in. double iron; 1 Joiner's Hammer,No. 2; 1 Claw Hammer, No. 1; Joiner's Mallet, 5 in.; All -Steel Hatchet, No. 1; 1 Cased Oilstone,8 in. ; 1 Joiner's Square, Gin. ; 1 Sliding Bevel ; 1 SpiritLevel, 6 in. ; 1 Spoke -shave, 21 in. ; 1 MarkingGauge; 1 Cabinet Turnscrew, each 4 in., 6 in.; 1 pair Pincers, (1 in.; 1 Handled Chisel, each 1 in.,

in., f in., 1 in.; Handled Gouge, 1 in.; 1 Joiner's Plain Brace, 9 in.; 1 Centre Bit, each 3 in., k in.,in.; 1 Special Auger Bit, each 1 in., In., 4 in., in., 1 in.; 1 Boxwood Rule, 2 ft.; 1 pair Com-

bination Pliers; 1 Putty Knife; 1 Paint Scraper; 1 Mitre Block, 0 in.; 2 Gimlets; 2 Bradawls ; 1 0 lisePot; 1 Cold Chisel, Gin. by I in.; 1 Tack Hammer; 1 6 in. Half -round File and Handle; 14 in.Saw File and Handle; 1 Centre Punch; 1 Nail Punch; 1 Packet of 12 Sheffield Twist. Drills;1 Pencil.

I DELIVERED on FIRST of SIX MONTHLY PAYMENTS of 1/51isive delivery area) 3,- England or Wales.

ELECTRICSOLDERING

IRONSA 1111e British made toolwith a six months guaran-tee against electrical break-down. Length 12 in. Fitted witha 6 oz. copper bit, loading 80watts. For A.C. or D.C. vol-tages, 200-220 and 240-250Complete with 2 yds. of twinflex, and adaptor. Please statevoltage. Post Gd 96

BOXES OF TWELVEASSORTED FILES

12 for

51Post9d.

The best and cheapest way to buy Files.British made and excellent quality. Sizes6 in. to 12 in. Also sizes 4 in. to 8 in.12 for 3/3. Post Gd.

SURFACE GAUGESAccurately made and fittedwith fine adjustment device.Overall height 12 in. Dia-meter of base 31 in. Posi 6d.

COLUMBUSPATTERNGAUGES

To take inside, outside,and depth measurements.Graduated to 5 in. and 120ram. and provided withtwo verniers which giveEnglish and Metric readings. Post Id.

HIGH -GRADEELECTRIC

HANDDRILLSat a very keen priceFitted with genuine Almond in. Chuck with key. Madefor voltages 100/110, 200/220, and 230/250. A.C./D.C.Speed 1200 r.p.m. Ball Bearings.Supplied complete with 10 ft. cab tyrecable.

Carriage paid in U.K.

IOR DELIVERED on FIRST ofSIX MONTHLY PAYMENTS of g

&ALI &DECKERVALVE TESTER

BORDEN TUBE TYPEPRESSURE GAUGE

Calibrated to 10 lb. persquare inch, but can becalibrated to approximatelydouble thispressure.Amazingvalue.Post 6d

Will work through any suitabletransformer. Rating, 12 to 14volts continuous, to two minutesat 24 volt,. Incorporating bi-metal thermal cut-out to pre-vent overheating and automaticclutch to avoid breakage undersudden stoppat,e. Reversingswitch, self-lubricating bearings.Rotor speed (noload) 2,000r.p.m. Outputspindle speed 58r.p.m.

Post Gd.

GEARED MINIATUREA.C. MOTORS (50 cycles)

74 lion isapprox.

one-thirdactual

sze.

STRONGADJUSTABLE

HACK SAWA heavy typesaw, takingblades from8 to 12 in.inclusive.Exceptionalvalue.

Post 6d.

SETS of

TAP HOLDERSWith six collets for taps upto in. Exceptionally tineworlimanshipand outstand-ing value at thisprice. Per set.

Post fid. 316

4'6

POCKET SET OF SOCKETFor radio,ignition andhousehold use.Marie in U.S.A

SPANNERSSmallest andmost compreben-ive 8 -piece set onthe market, com-

prising seven sockets a l

, and ?On. hexagon, iii.one handle. Sizes: 4, A Ai

round knurled, 1 in. square.Complete in steel rack asshown. Length: 41111.Post (5(t.

CANVASFold up when notin use. Three-plywood bottom. Co-

70 BAGS

ver strengthenedwith iron. Size:12 in. long, 6 in.deep, 44 inwide. Post 11d. t,

2'9INSULATED

PLIERS

Tested to 12,000 volts.Strongly made, insulatedwith thick rubber. In twosizes : 6 in.7in., 2/6. Post 6d. Post 6d.

To -day's Value 3/- and 3/9.

r.

SUPER QUALITY STOCKS and DIESMade in U.S.A. by Russell Manufac-

turing Co.Adjustable dies in 21 in.diameter collets, cutting 4,

log, 4, .4, 4,1 andworth threads with a tapertap to each size. Completewith die holder and tap

Packed in astrong wooden box. .17.6

OR DELIVERED FOR 231- DEPOSITBALANCE IN SIX MONTHLY PAYMENTS OF 11713

HEAVY DUTY,BLOCK TYPE

CONDENSERS1 MED. Capacity. Suit-able for voltages up to1,000 A.C. or 2,000 DA'.Tested to 4,000 voltsD.C. Dimensions approx-imately 41 in. wide, 9 in.overall height, 1 in.thick, Bake-

2,6lite case.Post 6d.

DAMAGES, HOLBORN, LONDON, E.C.1 Phone your order: .1101,born 8484 City Branch: 107 Cheapsi de, E.C.2

Published about the 30th of each month by GEORGE NEWNES, LIMITED, T(.. ver House, Southampton Street, Strand, London, W.C.2, and Printedin England by THE SUN ENGRAVING CO., Lm., London and Watford, Herts. Sole Agit : for Australia and New Zealand-Gordon & Gotch, Ltd. Sole Agentsfor South Africa-Central News Agency, Ltd. Subscription Rates : Inland and Abroad, 6d. per annum. Canada, 9s. per annum. Registered at the G.P.O

for transmission by Canadian .ag. zine Post.

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CIT'D JANCM · Naval Architecture Novel Writing Pattern Making Play Writing Police. Special Course Preceptors, College of Press Tool Work Production Engineering requirements above,