ANTI AIRCRAFT AND BREN GUNS - WorldRadioHistory.Com · 2020. 4. 18. · THE FLUXITE GUN is always ready to put Fluzite on the sol-dering job instantly. A little pressure places the

ANTI AIRCRAFT AND BREN GUNS

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2 NEWNES PRACTICAL MECHANICS October, 1940

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October, 1940 NEWNES PRACTICAL MECHANICS 3

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PRACTICALECHANICS

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

Editor : F. J. CAMM

VOL. VIII. OCTOBER, 1940. No. 85

WANTED -MINISTRY OF IDEAS AND INVENTIONSBy The Editor

An Old WishEACH of us is acquainted with an

individual who bemoans his fateand who is certain that he could dobetter " if he only had the chance."There are many of these who fail torecognise the opportunity when it arises,and whose lack of progress is due to thatlack of recognition. There is a school ofthought which presumes that a goodidea brings its own reward, and that thewhole world should acclaim the goodidea and pay its financial tribute to thecreator of it. The real skill is in thedevelopment and the marketing of theidea to the advantage of the one whoconceived it.

An idea may seem good, but itrequires considerable investigation ex-periment and development before thesnags are found. It may be discoveredthat the idea is not original. There maybe manufacturing drawbacks. An ideato be good must be successful, and to besuccessful it must be marketable.

Investigate Ideas

A s my years of experience in dealingA with inventors grow, and thevolume of correspondence increases,I am none the less forced to theconclusion that this country does notencourage inventive enterprise as muchas certain Continental countries. Whatis wanted here is a Ministry ofInvention and Ideas which will analyseand, if necessary, subsidise inventions,for the nation with the highest degree ofinventive faculty must eventually sur-vive. Inventors, in this country, arepositively discouraged from pursuingtheir ideas because of the apathy ofmanufacturers in general, and theGovernment in particular. This par-ticularly applies to poor people, who inmany cases cannot even find the few

pounds necessary to patent the idea.We require a panel of experts who cansift the value of ideas, if necessarypatent them and make advances to theinventor with, of course, a State interestin the profits as a return. In Germanysuch a system has operated for years.It may be that some thousands of worth-less ideas are investigated, but duringthe investigation the inventor is paida sum of money to proceed with hisexperiments, and out of the plethora ofworthless ideas and the refining furnaceof investigation emerge really worth-while ideas of value to the individual andto the State. And it is my view that theState should take control of its inventors,and not leave them to the thorny pathsof penury and to the exploitation ofunscrupulous speculators who buy upvaluable inventions for trifling sums.Very few inventors are business people,and more often than not they are cheatedof the rewards due to their labours.Many of them have, indeed, soldvaluable inventions to foreign countrieswhen they would have been of far moreuse to us.

The Post -War PeriodWHEN this war is over, there will be

a boom in certain industries whichwill be hard pressed to make up for thelack of production during the war.There will be a boom in engineering andin building, in toy -making and inautomobiles, to mention but a few of theindustries which have to make up theproduction time lost during the war.Now is the time, therefore, to lay thepost-war plans, to have the ideas ready;during the last war very few firms laidpost-war plans, and when the warsuddenly ended, as this one willsuddenly end, many firms suddenlydeprived of munition contracts wentbankrupt. Our main concern must be

to win this war, but equally we mustremember that it cannot last for ever,and if post-war depression is not todeprive us of the fruits of victory wemust now lay post-war plans. Inventorscreate trade. They must be encouragedand organised. We must regiment theirideas and exploit them to the nationalgood. We must not, in future, allowvaluable ideas to lie dormant for want ofcapital. It is essentially a job which theGovernment must tackle, particularly ifwe wish to capture foreign markets.The export trade of our enemies is ata standstill, and it should be the duty ofsome Government department here tolay such plans as will enable us, whenthe war is over, immediately to supplythose markets. We are doing a fairamount now in that direction, but thereare many (clocks and cameras, forexample) untouched.

In the words of Mr. Morrison, let usGo To It --Now !

Carrying OnTHIS issue has been prepared during

a series of air raids which have takenplace daily and nightly for a fortnight.But here it is, in your hands, punctuallyand, I trust, of unimpaired quality.London is, indeed, well in the firingline, and the crack of anti=aircraft fireand the dropping of the bombs in thevicinity leave the editorial staff undis-turbed. We have a service to perform toour readers and, in common with allother journals and periodicals, we carryon during and in spite of the war. Thepublic does not always appreciate thevast amount of work which goes intothe production of each issue, and whichthey obtain for a few pence per month.The small service that we ask inexchange is that you should place aregular order with your local newsagentfor its delivery to your door.


Anti -Aircraft and

At an anti-aircraft postsomewhere in England,showing the huge range-finder, and one of the new4.5 guns in the back -ground.

3ren GunsHow Britain Defends Herself Against Raiding Aircraft

N enemy bomber was shot downby anti-aircraft batteries earlythis morning. . . ." Behind this

f'ormal statement that yet one more Heinkelor Domier has been destroyed lies a storyof intense but ordered activity by anti-aircraft units. First comes the message,brief and to the point : " Enemy aircraftapproaching at position X. Height 12,000feet. Warn all batteries in area." Within30 seconds, the anti-aircraft crews are attheir allotted stations. Guns are loaded.Quick -firing Bofors, 3.7's, and big 4.5's areready to load the sky with menace. Thegun layers swing their long barrels into thedarkness, but as yet all is silent. Suddenly asearchlight shoots a long pencil of light intothe sky, and soon a dozen searchlights aregroping into the blackness above. Fromfar up in the silent sky, faint but unmis-takable, comes the sound of engines. Inthe beams of the searchlights, a speck isseen flying towards the east, and the enemyis " held.

The PredictorNearby is the predictor which is now

ready to play its part. Its complicatedcollection of knobs, lenses and dials cando the work of four men, telling the gunnerswhere to direct their fire. Dramatically andwithout warning, firing levers are .rammed

over, there is a reverberating boom and ashell leaps into the air, to explode with anorange flash thousands of feet in the dark-ness above. Other guns take up the chal-lenge and soon the enemy is under heavyfire. The sound of exploding shells growsmore distant, and again there is silence. Atelephone rings and a voice says : " Anaircraft, believed to be a Heinkel 1H,reported down in flames in a wood about12 miles from position X. Looks like one ofyour batteries. Good show 1 " That in briefis what happens every time raiders approachthis country.

When the last great war started therewere no British anti-aircraft guns in exis-tence. In 1915 an anti-aircraft howitzermade its appearance and it was nicknamed" Archie." This gun was followed by aporn-pom gun firing a one -pound shell, butthis proved unsatisfactory as its shell onlyexploded on impact. Next a 13 -poundermounted on a motor chassis for mobilitymade its appearance in 1916. This gun wasthe real " Archie " and it fired H.E. andshrapnel shells. From that time on verylittle progress was made in the developmentof the anti-aircraft gun.

Modern GunsDuring recent years, however, inventors

have concentrated on A.A. gulls and now we

have several types in use, each for a specialpurpose. The most familiar is the Lewisgun which is capable of delivering heavybursts of fire and requires a small crew tooperate it. It is used mainly for defenceagainst low -flying planes and is capable offiring 150 rounds a minute. It is chieflyused for local defence purposes at search-light positions. A similar type of gun is theBofors gun which is very effective againstdive -bombers. It is small compared withthe 3.7 or 4.5 A.A. guns, and fires a streamof tiny high -explosive shells, each of whichcan inflict serious damage to an aeroplane.A feature of the Bofors gun is the largesights which enable it to keep in focus anybomber flying at close range and high speed.

By simply turning a geared handle, thegun -layer can swing the whole gun roundvery rapidly, and the barrel can be raised orlowered equally swiftly. Clips of shells arefed in from the top of the gun.

The whole gun runs on four heavy-dutyballoon tyres, which allow it to be trans-ported quickly over rough country.

Guns With High CeilingA gun which has made its debut in this

war is the now famous 3.7 which has aceiling of over 30,000 ft. Messrs. Vickers -Armstrong carried out experiments nearlyten years ago with a view to producing an


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i HEALTITUDE 1FINDERIS ADJUSTED TO BEAT RIGHT ANGLES TOALTITUDE & COMPUTES& ELECTRICALLYTRANSMITS RANGETO PREDICTOR

ALTITUDE ATRIGHT ANGLESTO BASE

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5 -RESENT POSITION

ANTI-AIRCRAFT GUNSETTING OF FUSE& OF GUN(ALLOWING FOR DROF SHELL) AREELECTRICALLYTRANSMITTED BYPREDICTOR

PREDICTOR

REGISTERS TEMPERATURE, BAROMETRIC PRESSURE,4 DIRECTION OF WIND HOW ANTI-AIRCRAFT GUNS

t' ATTACK ENEMY AIRCRAFT AND THE METHODS OFCALCULATING THE VARIOUS FACTORS INVOLVED


efficient type of A.A. gun. The 3.7 was theresult. It fires a shell weighing 28 lb. andloading is " semi -automatic." When thegun is first brought into action the breachis operated by a hand lever, but as thebarrel of the gun recoils the breech opensof its own accord causing a spring tocompress and eject the empty shell case.At the side of the bore is a tray for holdingthe ammunition and this tray is brought intoline with the bore as the breech opens. Awire -operated ramming device is then usedto rain the shell home. which is then firedby a lever.

On the top of the weapon is a device fortaking up the heavy recoil of the gun. Thistakes the form of a compressed -air brakefitted in a metal cylinder. When in action.the gun is steadied by four metal feet whichare fastened to the ground. It is capableof firing 15 rounds a minute.

Rapid assembly is one of the mostimportant features of the gun, and it can beset up into position in a very few minutes.Electric batteries are carried by the gun,and the illuminated dials of its instrumentsenable the gun to be used during hours ofdarkness. It has a firing angle of eightydegrees, which is almost vertical.

Range -FindersWith this type of gun as well as our

4.5 A.A. guns a special predictor mechanismis used including long-distance range-finders. The earliest types of range -finderswere extremely cumbersome but prismaticdevices have now been introduced whichhave considerably reduced their size. At onetime it was necessary to have a range -finder100 ft. long to reduce possible technicalerror to 100 yards at 20 miles, or 10 ft.lone for 100 -yard accuracy at 10 miles. A

GAS PASSAGEFROM BARREL TOREGULATOR VALVECONTROLS RATEOF FIRE.

TRAP FORME TA L

number of these long range -finders are stillused on warships, but a new type of " coin-cident " range -taker is now used for A.A.guns which is shorter and more accurate.Two prisms with accompanying opticalgroup are used, one introducing a 90 -degreebeam to the observer, and the other showingan image at the eyepiece in a position that.depends on the distance. It can be likenedto the moving -image or double range -findersthat are used on many cameras. Twopictures of the target are seen by the opera-tor when he looks through the eyepiece,and they are brought together by movinga control. The correct range has been foundwhen thy two images merge into one andthe distance is read off on a meter.

The Sound LocatorTo further simplify the work of the

gunner, a device known as a sotind locates'is brought into operation. This is a weird -looking machine fitted with a number ofcup -shaped trumpets which act as giantears. The locator is mobile and the operatorand trumpets rotate around a common axis,the movement being carried out by theoperator. When enemy aircraft approach,the operator, who uses a stethoscope, rotatesthe locator until the noise made by theengines of the approaching aircraft is equallyheard in both earpieces of the stethoscope.The height and direction of the enemy air.craft can then be determined as soon as the" ears " of the locator are pointed directlytowards it.

As time takes an appreciable period totravel over a given distance, allowance musthe made for " time lag." The speed of soundis 1,100 ft. a second, therefore it would take10 seconds to travel 11.000 ft.. and this must

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be allowed for in the calculations sent to thegun crew.

The Bren GunYet another new gun suitable for low -

flying aircraft is the Bren, named after theCzechoslovakian town of Brno, where itwas invented. This light automatic gun iscapable of firing 500 rounds a minute, andis possessed of a high degree of mobility. Abipod is under the barrel, behind thetrigger is a fingergrip, and a folding shoulderrest is on top of the butt. A detachablehandle for the,left hand is on the undersideof the butt, and this enables the recoil tobe shared by the right shoulder and theleft arm, thus reducing the effect of thekick.

The Bren is mounted on a tripod whenused for prolonged fire, and the barrels arechanged after every 300 rounds to avoidoverheating. In addition to the "safety"there are two other trigger positions-"single shots" and "continuous." The lastposition is obtained by keeping the triggercompressed and the gun will then continueto shoot until the trigger is released or theammunition exhausted. Weighing only21 lb., the Bren is immensely strong.

New A.A. GunAn A.A. gun which has recently made its

appearance is a many -barrelled pom-pomgun which is suitable for use against, dive-bombing. It is used its conjunction witha balloon barrage. The balloons keep thebombers high enough to prevent accuratebombing, and if the enemy planes comedown tc shoot at the balloons, the new guncan get them. It fires shells of I -in. calibrewhich are so delicately made that theyexplode on the slightest contact.

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The Bren gun, which can be adapted for bench or anti-aircraft work. .1 crew of four men can keep this gun constantly firing-two to work thegun and two to bring up the ammunition. The gun can be adjusted to fire single shots or for continuous automatic fire.


Submarine MinelayingBy COMMANDER EDGAR P. YOUNG, R.N. (Rtd.)

THE submarine mine is essentiallyjust an explosive charge, containedin a water -tight case. It derives its

name from the fact that it is an adaptationof a similar weapon used in land warfare,which is laid underground, a process whichinvolves work similar to that in a mine.

As early as the sixteenth century itbecame a practice in naval warfare to usedrifting explosive charges in the same wayas fire -ships were already being used. Suchdrifting charges may, therefore, be regardedas the predecessors of the mine proper,which was used for the first time in 1777,by the Americans. Extensive and effectiveuse was made of the new weapon in theAmerican Civil War, and thereafter its usebecame ever more widespread, notably inthe Russo-Japanese War of 1905-6.

Submarine mines were first used by thiscountry in 1863, and were handled by theRoyal Engineers-who are responsible, ofcourse, for mining operations on land. Itwas not until 1904, moreover, and furtherdevelopments of mining warfare at sea thatthe inconvenience of this arrangementbecame so great that submarine mining wastaken over by the Royal Navy. Since thatdate it has been the responsibility of a specialsection of the Torpedo Department of thatService.

172,000 Mines Laid.Mine warfare played a very important

part in the Great War of 1914-18, as may bejudged from the fact that some 172,000mines were laid by the Allies and some44,000 by the Germans during the four yearsof that war. It is playing no less importanta part in the present war, both belligerentshaving already laid large numbers of minesand being constantly engaged in layinglarge numbers more, though it is improbable

that the numbers laid have yet reached suchenormous figures as have been quoted above.

The object of the mine is to cause suchdamage to the more vulnerable, and lesseasily protected, underwater portions of anenemy ship as will bring about her destruc-tion. In order to achieve this object, themine must somehow be detonated when itis in contact with the hull of the enemy ship,or at least when the hull of the enemy shipis within the destructive radius of itsexplosion. It is evident, therefore, that,except in waters which are so shallow thatthe hull of a ship passing over the mine must

commencement of this article, of an explo-sive charge, contained in a water -tight ease.

The shape of the case is immaterial, butis usually cylindrical or spherical. Thematerial of which it is constructed is, usruallysteel, but in certain circumstances-as, forexample, where the mine is to be laid byaircraft, or where it is a magnetic mine,aluminium, or some alloy of that light andnon-magnetic metal, is used ; for magneticmines in circumstances where weight is notof importance, the case may be made ofconcrete-which is cheaper than aluminium.

Contained in the mine -case is the charge-

A Brief History Of The Submarine Mine AndThe Important Part It Plays In Modern Warfare

come within its destructive radius, the minemust be buoyant. Furthermore, sincea mine which floats on the surface can beseen and avoided, and since the effect ofits explosion is greater in proportion as thedamage inflicted is below the waterline of-the ship, it is desirable that the mines shouldfloat at some given depth below the surface.What the depth should be must depend onthe draught of the ships which it is intendedto attack, on the method whereby the mineis detonated, and on the destructive radiusof the mine.

Types of MineIt must be obvious, of course, that the

development of mine warfare has led to theproduction of various types of mine, for usein various circumstances and for variouspurposes. Before going into that matter,however, it might be well to have a generalidea of the general design and constructionof a mine.

The mine consists, as was stated at the

of high -explosive. The explosive usedshould preferably be one which does notrapidly deteriorate with the passage of timeor on account of humidity. Wet guncottonwas the material which was originally used,and it is still used sometimes, but morecommon are ammonium perchlorate andamatol, the latter being a mixture ofammonium nitrate and tri-nitro-toluol(T.N.T.), which are less bulky than wetguncotton. Since, however, all nitrates areliable to deteriorate in the presence ofmoisture, a charge of pure T.N.T. is used formines which, owing to the material of theircase (e.g. concrete) or to the great pressureof water at the depth where they will lie,are liable to prove leaky.

DetonatorsAll these high-explosiyes require a

detonator to set them off, and the materialmost commonly used fcr these detonators isfulminate of mercury. The detonatingmaterial, being very delicate, is enclosed in


a metal tube or container, winch is de-tonated by mechanical or, more commonly,by electrical means.

The size of the mine is determined byvarious factors, among which' the moreimportant are the destructive effect whichis required and convenience of handling.The former depends, of course, on the typeof ship against which the mine is intended,and also, in the case of a non -contact mine(see later), on the destructive radius which isdesired. As it is usually hoped that themine will be exploded by a large ship, thecharge within the mine is made great enoughto bring about the destruction, or at leastto damage severely, a well -protectedbattleship, subject only to the condition thatit will fit within a ease of manageable size(and, where the mine is to be laid by air-craft, that the total weight will not beexcessive). Smaller mines may, however,and frequently are, made for variousspecial purposes, being used, for instance, inconjunction with the larger mines, to pre-vent the latter being swept.

The majority of the mines which are usedare of the moored type (see later). Thesehave attached to the mine a considerablelength of mooring wire, wound on toa drum within the mooring device, whichis known as the " sinker." Drifting minesa-nd non -buoyant mines obviously ha to notneed of this appendage.

The types of mines in common use may bedivided, for purposes of this article, underthe following headings and sub -headings( ) Moored mines

(2) Mines without

(a) Observation mines(b) Contact mines(c) Non -contact mines(a) Drifting

moorings (b) Fixed

Observation MinesThis type of mine is used for the protec-

tion of harbours, anchorages or channelswhich can be kept under observation. Theyare usually laid to float at ,such a depthbelow the surface that they will not normallydisturb or be disturbed by, passing ships ofany size, though they would obviously bedisturbed if a ship were to anchor amongthem. They are wired up to an observationstation, usually on shore; from which theycan be detonated singly or in groups byelectrical means.

Owing to the fact that, when they de-tonate, they are not actually in contact withthe ship which they are intended to destroy,and since they can be laid in circumstanceswhere ease in handling is not of predominantimportance, they are usually larger thanother,types of mine, and have a larger des-tructive radius.

They are laid in fields, the contours of-which are marked on secret charts and ofwhich the exact position of each componentmine is marked on a special chart fixed inthe observation post in such a way that theexact position of any enemy ship can beprojected on to it. The observer can thusknow exactly which mine, or group ofmines, he should detonate in order to des-troy the enemy.

It is mines of this type which haverecently been constructed and laid in suit-able places round the coast of Fire.

Contact MinesWhere mines are laid in enemy waters, in

the open sea, or in any other place where itis impossible to maintain an observationstation, such mines must be fitted with someautomatic device which will detonate themat the right time. The most obvious way toachieve this is to fit them so that theydetonate when an enemy ship comes incontact with them, for that ensures that

they will have the maximum of dust mei iyeeffect.

In the earlier contact mines, detolytionwas effected mechanically, the passing shipcausing a rotating arm to revolve untila spring plunger was released and wouldstrike the detonator. In modern mines.however, . the detonation is effected elec-trically in the following manner. On theexterior of the mine -case there are severallead -covered horns, each containing a glassphial of acid. If a passing ship strikes oneof these horns and crushes it-or, alterna-tively, 4 she causes the mine to heel through anangle of over 25 degrees -the acid spills intoa cup, completing an internal electricalcircuit, whiCh fires the detonator.

Mines of this type need a. smaller chargethan the observation mines which havealready been described, or than any type ofnon -contact mine, such as will be described.

Non -Contact MinesThe earlier mines of this type were fitted

with antenna; winch radiated from them toa radius of 35 feet or more, and were

Such mines may 1,st useful as a weapon foruse by a retiring fleet to weaken or to holdoff a pursuing enemy or for floating down-stream, or down tide, against enemy shipswhich are suitably placed to be so attacked. .They have many obvious disadvantages,however, and are, therefore, likely to beused only by a fleet which does not intendto use the sea himself. -

New TypeFloating, as they usually do, on the sur-

face of the sea, they can be avoided if oneis vigilant and manoeuvres quickly. A typehas been invented, however, and maysubsequently have been developed, whichhas negative buoyancy and would normallysink to the bottom, but which is maintainedat some given depth below the surface bya propeller beneath it driven by a hydro-statically -controlled motor inside the mine -ease.

Fixed MinesTins it the most common 1 ype of mag-

netic mine. It has no " sinker," 'but sinks

Assembling and loading mines at a submarine mine depot.

fired when a passing ship came in contactwith any of these.

Such mines did not prove very satis-factory, however, and the modern non -contact mine is fired by magnetic meanswhen a steel ship passes within about 50 feetof it. The process by which this is achievedcannot yet be revealed for reasons of neces-sary secrecy.

It is laid down by the Hague Conventionof 1907 that moored mines shall be pro-vided with a safety device whereby they arerendered innocuous as soon as they breakadrift from their "sinker." Such a device isnot always fitted, however, and even whenfitted it does not always operate satisfac-torily, so it often happens that . a mooredmine becomes a. " drifting mine."

Drifting MinesThe drifting mine proper, on the other

hand, is a quite legitimate weapon of war,winch is recognised by the Hague Conven-tion of 1907 subject only to the conditionthat it must be so designed -that it becomesinnocuous one hour after it has beenlaunched.

The simplest type of drifting mine is ineffect merely a contact mine without anymooring's and with the normal safety deviceeither removed, or rendered inoperative.

to the bottom and remains there, beingdetonated when a steel ship comes withinabout 50 feet of it

Such mines are obviously useful againstsurface ships only in comparatively shallowwaters, and preferably in a narrow channel,but may be useful also in deeper watersagainst submarines, especially in placeswhich are suitable for them to settle onthe bottom for a rest or to escape detection.

Having dealt with the various types ofmine, it might be useful, in conclusion, todeal briefly with the purposes for which theyare, and the circumstances in which they canbe used.

The original purpose for which mineswere used has already been stated, in con-nection with the Observation Mine : fordefending an anchorage, harbour or channel.Out of this has developed their use for thewider purpose of denying enemy ships theuse of any part of the seas. When used forthis purpose, they form, as it were, additionaland highly dangerous new shoals, the exist-ence of which is not always known and thelocality of which, if declared, is alwaysrather conjectural and approximate.

Mining of this type can be done only withmoored mines, of course, and such mines canbe used only in waters which are shallowenough for the mine to be able to support

October, 1940 NEWNES PRACTICAL MECHANICS

VARIOUS TYPES OF MINES AND HOW THEYARE DETONATED

HARBOUR PROTECTEDBY CONTROLLED MINES

OBSERVATION POST

CONTROL BOARDCABLES TO MINEFIELDWHICH CLOSE ELEC--TRICAL CIRCUIT ANDDETONATE EXPLOSIVE

MOORED MINE EXPLODES ONCONTACT OR IF TILTED MORE

irHAN 25°19Y WASH OF THE SHIP.

MINESDROPPED

BYPARACHUTE

FROMAIRCRAFT

THE SINKERANCHORS

THE MINE

MAGNETIC MINEEXPLODED BYAPPROACH OF METALHULL OF THE SHIP

MINES ADRIFT FROM THEIRSINKER ARE EXPLODED BY

RIFLE FIRE

LaROKENCABLE

10 NEWNES PRACTICAL MECHANICS October. 1940

the weight of its mooring wire, i.e., witha depth of not more than some 600feet.

Setting the SinkerWhen the mine is laid the depth below

the surface at which it is required to floatmust be set on the sinker. It assumes thatdepth automatically soon after, or, if it. is sodesired, at a given period of time after it islaid, and then it remains at that distance fromits sinker. Now it is obvious that in tidalwaters any fixed distance from the sinker

does not mean a fixed distance from thesurfitce. The latter must clearly vary wit Itthe state of the tide, with the result that atone state only-usually at half-tide-is themine at the ideal distance below the surface.It may happen, therefore, that at highwater the mine is too far below the surfaceto be a danger even to the largest ship, whileat low water it is exposed upon the surface.It may happen also, in places where the tidalstream is particularly strong, that the minecan float at its appointed depth onlyduring short periods of time around slack

One Hundred Octane !A Super Fuel for Super Aircraft

ONE answer to the insistent call ofaircraft designers, in their never-ending search for higher speeds and

increased performance, has been found inthe more powerful fuel now being producedby modern science.

The amount of power which can be wrungout of a single drop of petrol is largelydependent upon the degree to which thepetrol vapour can be compressed in theengine without the engine " knocking."Recent advances in the technique offuel refining have now produced fuels whichpermit enormously greater compressionratios. They are generally referred to as" high octane " fuels.Modern Fuels

Modern fuels, both automobile andaviation grades, are given an octanenumber, according to their non -knockingqualities. The octane scale ranges fromabout 56 in straight run or low-gradepetrols, 65 to 75 for " cracked " petrols,and 70 to 75 for high-grade fuel withtetra -ethyl lead, up to 100 in the latestaviation products.

To determine the octane value the petrolis compared, in a standard test engine,with various mixtures- of two pure hydro-carbons. One of these, iso-octane, ispractically non -knocking; the other, hep-tane, knocks very readily. The particularblend of these two ingredients whichcorresponds in knocking characteristicswith the petrol being tested gives theoctane number.

It has been calculated that high-octanefuel increases the power output of a modernaero-engine. by something like a third ormore. For the same power output smallerengines and consequently lighter fuel loadsare required.

Extremely Valuable

Produced until recently only in smallquantities, a 100 -octane fuel was so valu-able that it was used only for take -off, andspecial flights. Now in America, whereroughly two-thirds of the world's petrol isproduced, special plants planned for aproduction of many million tons of 100 -octane fuel a month are being developed.

Two -Motor Trainer of the R.A.F.How Pilots Are Trained in the R.A.F.

STANDARDISED methods of Hyinginstruction have long been a strong pointin the training of the pilots of the R.A.F.

Integral with a standard syllabus oftraining is the use of a standard type of- trainer " aircraft for the different phasesof the pupil pilot's instruction.

Pilots destined for twin -engine bomberand fighter squadrons learn the elements oftwo -motor technique on the AirspeedOxford-a fast, low -wing monoplane speci-ally designed for the job. In generalappearance it is not unlike the Envoy, amedium-sized civil type of aircraft pro-duced by the same constructors.

The Two MotorsThe two motors fitted to the Oxford,

Armstrong-Siddeley Cheetahs, each of 375h.p., give a maximum speed of about 190m.p.h. They are air-cooled radials, a typeof engine commonly fitted to the tiin-engine operational aircraft of the R.A.F.

A retractable undercarriage, oxygenapparatus for high -altitude work, Handley -Page slotted ailerons, and other features ofmodern operational aircraft are incorpor-ated. Its wing span of 53 ft. is a little lessthan the famous Anson, whilst its range ofsome 900 miles affords plenty of scope forlong-distance training flights. Evidence ofits speed and endurance is seen in a recordflight of one of the Oxfords in service with

the Royal New Zealand Air Force. Fittedwith an automatic pilot and carrying surveyinstruments, it covered the 680 milesbetween Hobsonville and Christchurch in3 hours and 40 minutes.

The CrewNormally a crew of three is carried. But

as the Oxford is used for training othermembers of an air crew besides the pilot,six different stations are provided. In thenose is the pilot's seat, and beside him isthe second pilot or navigator. The controlsare dual and one set is removable to makespace for the prone position for the bomb-aimer. Other positions are those for thewireless operator, rear gunner, and photo-grapher. In this way the Oxford caters forall the different functions of a bomber'screw, which in a big ship may number asmany as seven or eight.

In the R.A.F. the Oxford is used mainlyduring the intermediate stage of the youngpilot's training. This takes place at theService flying training schools, after leavingthe elementary training schools from whichall embryo pilots graduate. It is alsoemployed at the special schools where twin -engine fighter pilots are trained. Not untilthey have thoroughly mastered the Oxforddo the fully-fledged pilots go on to the" real thing "-the powerful bombers andtwo -motor fighters of the R.A.F.

atcr.All these considerations must be taken

into his calculations by the minelayer, andcircumscribe to a great extent his activities.He must also bear in mind always that hissuccess will depend largely on his being ableto lay his mines unobserved. It is for thislast reason that the laying of mines by air-craft,though quantitatively bound to remainof insignificant importance compared withthe laying of mines by older methods. isbeing so actively developed by both sidesin the present war.

Adding " ToneTo The Piano

LAI U RENS HAMMOND, an American, has1- invented a musical device which hecalls the Solovox. It is a musical supple-ment to the piano and is operated entirelyby electricity. The Solovox is a three -octave keyboard which is attached to thepiano so that the fingers of one hand caneasily span the two keyboards. Twelvecontrol tablets give the Solovox a six -octave range as well as an indefinite varietyof tone colours. Because it is smoother andcapable of "swell," these tone colours makean effective contrast to the percussiveeffects of the piano. A knee lever controlsthe volume and a slim tone cabinet con-taining the electrical equipment ie setalongside a vertical piano or underneath agrand piano.

19

Laurens Hammond aided by one of his mechanicalexperts as he tests his newest invention which he

calls the &locos.

New Automatic RifleTHE United States Marine Corps are

testing out a new type of semi -automaticrifle. General Holcomb stated, after a pre-liminary test of the gun that it may be thecomplete answer to what they need. TheMarines at present use the U.S. Army'sGarand rifle, capable of firing 24 shotsa minute, which army ordnance expertshave said is the finest rifle of its kind in theworld, but the Marine Corps claims that itis not rugged enough for field service.

THE LEADING WEEKLY FORENGINEERS

PRACTICAL ENGINEERING4d. Every Thursday

October, 1940 NEWN ES PRACTICAL MECHANICS

Producer Gas Motor Fuel

Producer -gas vehicles attached to various types of vehicle

SINCE petrol -rationing commenced aconsiderable amount of attention hasbeen directed toward the use of

alternative fuels for motor -car and com-mercial -vehicle engines. At first it seemedthat paraffin and vaporising oil would pro-vide the best solution to the problem of ob-taining fuel, but it became illegal for thevehicle operator to obtain these in ordinarycircumstances for use in modified engines.

Coal gas also came into prominence atthe same time, and is being fairly widelyused at the present time-as it was duringthe last war. This provides an efficientfuel, but there are several drawbacks whichprove serious in certain circumstances.In the first place, if gas is stored in a low-pressure bag mounted on the roof of thevehicle only a very small mileage can becovered with one filling of the bag. Thus.thg method of storage can be consideredsuitable only for vehicles used mainly forshort -journey routes in town or near aconvenient gas -supply point. It is, ofcourse, possible to increase the "mileageper fill" very considerably by carrying thegas under very high pressure in steelcylinders. Here there are other difficulties :

the cylinders are very heavy and are noteasy to obtain at present; they are expen-sive; special plant is required to fill themunder the necessary high pressure; re-

filling cannot be carried out easily at theaverage garage, as it can when low-pressurebags are employed.

Overcoming DifficultiesAs an alternative to the above systems

further attention was directed toward theuse of producer -gas. This method es as byno means unknown or untried, but therehad been many practical difficulties inpre-war days. As a result of furtherresearch, however, three or four firms wereable to produce successful producer -gasplants which were free from nearly all ofthe objections which had previously beeninherent.

The idea of the producer -gas installationis that the gas is produced in an installationwhich is carried on the car or mounted on atrailer which can be towed by the vehicle.The gas differs from coal gas, and consistsvery largely of carbon monoxide. It does,.however, contain hydrogen, methane andnitrogen, as well as a certain amount (keptas small as possible) of carbon dioxide.

How the Gas is MadeMany readers will be familiar with the

method of producing carbon monoxide byburning coke,- coal, anthracite, or similarfuel in air. As the glowing carbon -contain-ing fuel conies in contact with the oxygen

The Operation Of Producer -GasUnits And The PossibilitiesAs A Fuel For Internal-

Combustion Engines

By FRANK PRESTON

of the air, carbon monoxide is formed.In practice there is often an intermediate

formation of carbon dioxide, but this gas isnot of value as a fuel. Consequently, theaim of the designer of producer gas plants isthe create a "local hot spot" so that theintermediate stage is almost completelyeliminated.

In practice, producer -gas is formed bydrawing air through broken coke, anthra-cite, etc., which has been raised to in-candescence. Instead of air it is possible touse steam, but this is less convenient in theease of a plant of the type under discussion.On some types of producer -gas plant a finespray of water is passed through theincandescent fuel along with the air,so that the effect is similar to that whichwould be produced when using steam. Onthe other hand, some makers of these plantshave been able to secure high efficiencywithout the use of the water spray.

At this point it may be asked how andwhy it is possible to replace the liquidpetrol normally used for an internal-com-bustion engine by a gas. It should beremembered that petrol is what is known ashydro-carbon-that is, it consists of h',dro-gen and carbon in combination. Before itcan be used to drive the so-called petrolengine, the petrol must be divided intovery small particles in the form of a spray.This is done by the carburetter, which alsocauses a certain proportion of air to bemixed with the spray. By this time thefuel can be considered as being almost inthe form of gas, so it would appear morereasonable to use a gaseous than a liquidfuel.

Notwithstanding this, petrol is the mostefficient and convenient form of fuel atpresent known. Producer -gas causes theengine to develop between about 60 and75 per cent. of the power developed by thesame engine when fed from petrol. Theefficiency can be increased, however, byincreasing the compression ratio of theengine and by providing a full manualcontrol of ignition timing.

Built-in and Trailer TypesProducer -gas plants are of two main

types : for building into the bodywork ofthe vehicle and as trailers for towing behindthe vehicle. The former is in many respectsmore pleasing, but the latter is better inthat additional weight is not thrown on tothe vehicle chassis and that body space isnet taken up by it. In connection with thetrailer, however, it must be rememberedthat the legal speed limit of the vehicle isthen restricted to 30 m.p.h. on both built-up and " derestricted " roads.

The total cost of a producer -gas plantnaturally depends to a certain extent uponits size, but an . average figure is in theregion of £100. Without fuel, a trailer unitcan be expected to weigh about 10 cwt.,but there are variations according tomake and output capacity.


Practical DetailsA diagrammatic arrangement of a

producer plant is shown in an accompany-ing illustration. It will be seen that thereis a large cylinder which acts as a fuelhopper and fireplace, and that there is anopening for the air near the base. Thiscylinder generally measures about 20 in.'in diameter by 4-5 ft. in length. Air isadmitted through a tuyere or pipe, which isoften surrounded, by a jacket through whichwater from the cooling system of the carcan be passed. This tuyere projects rightinto the heart of the fire, where the fuelreaches a temperature of between 1,000and 1,500 deg. C. Opposite this there is anoutlet through which the gas is drawn byengine suction. It should be noted at thispoint that there is no danger of gas pressurebeing built up within the cylinder, since theproduction of gas is dependent almost,entirely upon a good draught of air beingprovided by engine suction.

When the producer -gas leaves the fire it isnaturally very hot and is thus expanded tosuch an extent that it is " weak " or of lowdensity. It is therefore passed through acooler, which may take the form of anexposed cylinder. Next it must be cleaned,since it contains various impurities andalso small particles of coke and clinkerwhich would very shon score the cylindersof the engine. A cleaner is thereforeprovided, this being built according to oneof many designs. In some cases finely -broken cork is used as a filtering medium ;in other cases use is made of sisal and oil -soaked coke. So-called dust boxes arealso included in some designs, these beingarranged so that particles of dust and dirtcan " settle " from the gas before it ispassed through the final filter. After filtra-tion, the gas is passed to a gas carburetteror reducing valve where extra air isadmitted to provide the ::rust mixturestrength.Operation

Starting up of the tire is a simple matterand may follow the same lines as the methodadopted for a kitchen stove. Initially,however, there is the problem of creating

Air

Hopper

Tuyere

(Water cooling

the necessary draught, and this is some-timee overcome by fitting a simple electric-ally -operated fan, fed from the vehiclebattery. Another method is to start upon petrol-fed through an ordinary petrolcarburetter --and then to change over toproducer -gas after the engine has beenrunning for a. few minutes. By graduallychanging over to the gas it is possible tokeep the vehicle running. When thismethod is followed, or when there is anelectric fan, lighting of the fire is simplified.for it is possible to apply a paraffin torch orburning shavings to the air inlet; the flameis drawn into the fire and soon sets the fuelalight. Some designs have a built-inlighter box containing a wick which issprayed with paraffin and then set alight.

When the engine is stopped the fire willcontinue to burn slowly for a short time,(generally up to about 20 minutes) and theengine can be restarted without thenecessity for applying a dams. After longerperiods of stoppage, up to about an hour,

Filler Filter

FuelRefractory

lining

FireHot gas

Fire Box Cover

A gas producerunit and how it is

coupled to a vehicle

...,"""Clean gas to engine

Cooler andOust box

This diagram illustratesthe general principles ofthe producer -gas generat-ot. All details areomitted for simplicity

it is necessary to start the engine on petroland then to change over after sufficientdraught has been created to raise thetemperature of the fuel.

Maintenance of these producer -gas plantsis very simple with most of the presentdesigns. Coke and clinker must be removedfrom the fire grate about once a day, andthe filtering medium must be replaced at,say, weekly intervals. Most of the producerswill give upward of 200 miles of running pereharge of fuel, and the cost of fuel for a givenmileage can be expected to he about one -quarter that of petrol for the same engine.

ConstructionBecause of the apparently simple nature

of the producer -gas installation there aremany vehicle owners who have consideredthe possibility of making their own plants.It can be stated, however, that this isnot a feasible proposition unless there areample engineering -workshop facilities andthe worker is a skilled man. Even then.

t here is the difficult yof obtaining anefficient design, formany manufa c-ot rers have spent

large sums on de -v lopmentwork andcould not be expect-ed to make publicthe results of theirresearch.

Tt is not withoutinterest that the De-partment of Minessortie time ago setup a committee toinvestigate thepossibilities of pro-- ducer-gas plants,and that they will

supply details of Weir final design to bonafide manufacturers. It is their wish.however, that drawings and full detailsshould not be published.

It should be made clear that the detailsgiven above do nc apply to any particularproducer -gas plant, but are general incharacter and intended only to clear upsome of the misunderstandings which exist.


Learning the Morse Code

Fig. 2.-A practicaloscillator in theoretical

and practical form

THE first step in mastering Morse, is,of course, to acquire a knowledge ofthe code, and for those who have not

yet done so we give here the alphabet, andalso the grouping of the letters in " oppo-sites " and by learning the latter, it is notsuch a difficult matter to remember thesymbols. It is necessary to learn thesymbols by the " tune " of the letter, andnot merely to remember, for instance, that" J " is dit, dah, dah, dah. As an aid tomemory in this connection you may makeuse of the following phrases for certainletters. For the letter ' F " memorise the

ALPHABET FIGURES

A

CD

E

G

JKLMN

B

QRS

U

P

X

Y - - - -Z -

OPPOSITES

Fig. 1.-The morse alphabet with oppositesshown for memorising

phrase, " Did it 'urt yer "'

for the letter" L " (the opposite of " F"), remember,-" Of course it did." For " Q " memorise" God Save the Queen." As an opposite to" Q " the letter " Y ", remember theopposite of the " Q " phrase-" Queen, theGod save."

FiguresThe figures are quite easy to remember,

How to Acquire Speed in Readingand Sending Morse Signals

the numbers 1 to 5 being dots in that order,and 6 to 0 being dashes in that order, eachnumber totalling five dots or dashes. Thus,1 is 1 dot followed by 4 dashes. 2 is 2 dotsfollowed by 3 dashes and so on. Havingmemorised the symbols it is now necessaryto acquire practice in reading and recog-nising them and in this connection there aretwo simple schemes. In the first you canobtain gramophone records; and in thesecond you can send the symbols by meansof a key and oscillator-listening to yoursending over a loudspeaker or in a pair ofheadphones. For the oscillator you needa valve of the General -Purpose' type, anL.F. transformer-any ratio will do-andthe necessary H.T. and L.T. supplies. Theseare wired as in Fig. 2 and the key insertedin the H.T. negative lead. The H.T.voltage is critical, and if too low or too high,an audible note will not be obtained whenthe key is depressed. Adjust the H.T. untila suitable note is obtained, and thus anH.T. battery tapped at frequent intervalsshould be used. The records are obtain-able from Columbia (Nos. 326214), and fromF. L. Masters. The former consists of a setcommencing with the code and figures andpassing on to commercial messages all sentat a nominal speed of about 20 w.p.m. Abook is supplied with the records, givingthe translation, but unless you have a clock -

A

work gramophone motor capable of beingslowed down considerably you may findthese records are a little too fast for a start.The majority of electric turntables cannotbe slowed down to bring these records slowenough for a beginner. We might alsomention there are one or two mistakes in thepublished translation-so don't follow thecode symbols -in the book too rigidly if youintend to use the printed matter for practicepurposes.

The Masters record is at a nice slow speedand may be speeded up with a clockworkmotor to 20 w.p.m.,but again, the smallspeed control affored with most electricmotors will probably only enable the speedto be controlled between approximately6 w.p.m. and 12 w.p.m. There is also a slipin this disc, the omission of the letter rin Northern in the message on the secondside.

Acquiring SpeedThese records are mainly for reading

practice, but both may be used for sendingpractice and at the same time will enableyou to increase your reading practice orpowers of concentration by adopting thefollowing procedure. An amplifier with aninput mixing circuit is needed so that theoutput from the pick-up and the outputfrom an oscillator such as has already beenmentioned may be mixed. If you do notpossess an amplifier you can use your ordin-ary radio receiver, provided that it isprovided with pick-up sockets or terminals.Two separate volume controls are needed,one across the pick-up and one across theoutput from the oscillator. These are leadsbeing joined to the pick-up terminals orsockets. Using, for instance, the firstColumbia record in the set mentioned,adjust the volume control until the notefrom the record is approximately the samelevel as that delivered from the smalloscillator when the key is depressed. Withthe copy of the message before you, start thepick-up and take hold of the key. Themoment the message on the -record com-mences, start to send and endeavour to readfrom the copy both the letter and thesymbol as printed, at the same time sendingthe appropriate dot and dashes, keeping thenote from the oscillator in step with thepick-up note. At first ycu will probably

Fig. 3.-How to connectpick-up and oscillator out-puts for mixing as described

in the text

PICA -LP

our k -u; TRA?..5,--aettER


find it difficult to obtain one note from thespeaker, but as your oscillator will un-doubtedly be of a different pitch from therecord note you will quickly see whetheryou are lagging behind or sending too fast.This practice will not only enable you toconcentrate better, but will control yoursending speed and ensure spacing and at thesame time familiarise you thoroughly withthe symbols for each letter.

Speed AidsThe drawback normally with a record is

that von will become familiar with the

message, but this method of sending withthe record will give you ideal practice insending, and by speeding up the record youcan acquire perfect practice at sending upto 20 or 25 w.p.m. with correct spacing. Ifyou can devote one hour a day to this typeof practice you will soon be able to identify thesymbols without having to "translate" eachone and will soon acquire the necesssary speed.

When endeavouring to increase speed itis desirable to obtain a message at a speedgreater than you can normally manage, Itwill be found that you have to work two orthree letters behind, but when a symbol

comes which you cannot immediatelyidentify, don't wait and try to sort it out butforget it and go on to the next letter. Inthis way you will keep up With the speedand gradually the " faulty " letters willdrop into line until every symbol is im-mediately recognised. Do not keep trying toread at speeds which you can do comfort-ably. Always try and work beyond yourcapabilities so that you force yourself intospeed. Thus with the records, set them sothat they are going just too fast, and whenpicking up code stations select one whichyou find just a little beyond you.

Protection Against Incendiary BombsAn Important NewDevelopment in Fire

Fightingsolution partly mixed with CO, gas, whichwill extinguish most types of fire in effectivefashion. In addition the jet is completelyharmless under any circumstances, and hasthe further advantage of being intensely coldbecause of the liquefied gas, whilst it is anon-conductor of electricity, and safe upto at least 25,000 volts.

Dissolving Mixed SaltsFor incendiary bombs it is merely

necessary to dissolve the mixed salts inthe water used for filling the extinguishers,forming a concentrated solution. Whenthis is directed on the incandescent bombthe water evaporates and leaves the solidsalts which, on the same lines as the drypowder method, melt and extinguish thecombustion by sealing the crevices and localcooling. It will be remembered also that inthe firm's '` C.T.C." extinguishers forpetrol, benzol, and oil, and for motorvehicles in general, the same compressed0, method is used to propel carbon

1(1 blonde without the use of a pump.

Typical incendiary bombs extinguished almost in a few seconds by the -1\hiswift" bomb snuffer

pROTECTION of engineering works,garages, repair depots, and otherindustrial establishments against in-

cendiary bombs can now be given, on mosteffective lines, as the result of an importantnew development in fire fighting.

The incendiary bomb is of small size,weighing about 2-6 lbs. and has a casingor body of electron metal (magnesiumalloy) which contains a charge of "ther-mite " (a mixture of powdered iron oxideand granulated aluminium) ignition of thethermite takes place by an impact detonatorof the needle and percussion cap type, anda tremendous heat develops, about 4,582' F.(2,500' C.) which ignites the electron metalcasing, the latter then burning in the air,developing a temperature of about 2,372° F.(1,304' C.).. To extinguish such a bomb isextremely difficult, since the oxygen forthe combustion of the thermite, which lastsabout 40-50 seconds. is obtained directfrom the iron oxide and not from thea t mosphere.

Inorganic SaltsThe effective new method, however, the

invention of The Nuswift Engineering Co.,Ltd., of Elland (Yorkshire), consists essen-tially in the use of a mixture of inorganicsalts which are brought into contact withthe incandescent bomb and become molten,extinguishing the main burning of the.

electron metal bomb casing by choking thecrevices and preventing air admission and.also by reducing the temperature bycooling to below the ignition point. In thisway an incendiary bomb can be ex-tinguished easily and safely in about20-25 Seconds, although it is necessary towear coloured glasses, such as the standardGovernment type, as a protection againstthe glare. Two general methods of applica-tion are used, the first of which is called a"bomb -snuffer," consisting of a metal cover,like a large candle snuffer, containing acharge of powder in a paper carton with acelluloid seal, which is placed bodily overthe top of the bomb. This is particularlysuitable when the bomb is on a flat floor orroof, or otherwise easily accessible. Evenmore important is the second method,which is to use the firm's standardhand extinguisher.

ApplicationFor normal application the latter contains

water and a small sealed seamless coppercanister of compressed carbon dioxide(CO2) gas under pressure. All that isnecessary when operating the extinguisheris to press down a knob, when an internalsharp point pierces a thin copper sealcover of the canister and releases the CO.,into the water, giving at once a high-pressure jet of water, containing CO., in

BOOK RECEIVED(Sec also pages 25 and 31)

" What Engineers Do." By Walter D.Binger. Published by The Scientific BookClub. 304 pages. Price 2s. 6d. to members.

N this book is told, in simple language,I the story of civil engineering andconstruction. It is an outline of what. hasbeen accomplished in this great field fromthe time of the early Egyptians to the..present. The methods by which great-.difficulties were overcome are clearlydescribed with the aid of numerous illustra-tions. In the wide field covered by thisbook are included such subjects as The'Steel Age ; Concrete ; Working UnderWater ; Surveying ; Aerial Photography ;Bridges; The Modern Building; The Rail-road ; Hydro - electric Development ;Strength of Materials, and Keeping theWaters Pure. The hook is divided into1,-..ety-two chapters, all of which make

readitig.

DIESEL VEHICLES : OPERATION

MAINTENANCE AND REPAIRBy F. J. CAMM

bq11, r 1,111. , 1;0.1'

11,,,,,,


Our Busy InventorsA Sound Hat

THAT fickle jade, Dame Fashion, is nevermore capricious than when she designs

the head-dress of the fair. Sometimes shefancies a hat which spreads itself like a greenbay tree. Anon she contracts this to theminimum of head covering, which rides at arakish angle on her permanent waves.'Admittedly, one of the most intriguingstyles is known as the Pixie Hood. It is thekind of cap that surmounts the fairy spriteswho gamble in the court of Queen Titania.This hood may be made of oilskin, wool,cloth, or fur. There are extensions or tapeswhich tie under the chin.

Principally intended for rainy days andthe wintry season, the hood keeps the earswarm and dry. Some of these caps areformed with openings for the ears andshields to protect those shell-like receivers.But, while they guard the ears against theassault of raindrops and the sharp teeth ofJack Frost, they also exclude sounds, sothat sweet nothings are denied admission.

This brings me to an improved style ofPixie Hood which is the subject of anapplication to the British Patent Office. Itis differentiated from its predecessors byapertures at the sides which admit sounds,but are provided with inverted pocket -like covers to exclude rain and icy winds.

By the way, the Pixie Hood is an excellenthead covering for ladies in an air-raidshelter which is occasionally raided by coldair that assaults the ears of the shelteringones.

Premature BurialTHERE is on record the account of a man

who suffered with the delusion that hewas dead. To humour this queer belief, hisfriends made a pretence of burying him. Itmay be asserted that some inert folks areafflicted with the hallucination that theyare alive, whereas, if not quite deceased,they are, like one of Thomas Hood'scharacters, rather dead.

Some nervous people are afraid that theywill be buried alive. To prevent such anunpleasant experience, an inventor hasapplied to patent in this country means forensuring against premature burial. Hestates that many medical tests have beenprovided to prove that the alleged deceasedis really a fit subject for a funeral. Suchtests, he declares, are not always reliable,even when performed by a skilful medicalman. He mentions the fact that it has beenproposed to place in the coffin a sort ofalarm clock which would be operated bysome movement on the part of the revivingbody.

His idea is to make quite sure that theoccupant of the coffin -is really a corpse byan arrangement whereby there is generated

'within the coffin a gas which will preventany return to consciousness. This appearsto be a merciful method, but I recall thefact that the author of the famous romance," llanon Lescaut," which has been madethe subject of an opera, was killed by hispost mortem.

Portable SearchlightTHE searchlight is, in the present day-

or rather night, the cynosure of all eyes ;in fact, its fierce glare provides its ownpublicity. Considerably smaller than thisGargantuan hull's -eye, but larger than the

I IL y " Dynamo "humble electric torch, there has emanatedfrom the brain of an inventor a portablesearchlight. The batteries are fitted in afiat bundle designed to be carried on theback. An 85,000 candle -power bulb will pro-ject a brilliant beam a quarter of a mile,and the spotlight is fired by a trigger. In-tended for the police, firemen, sportsmen,and others, the lamp can be supplied withcoloured lenses which snap over theordinary lens for signalling or warning.

Roof -PoolsTHE present may be dubbed the Pool

Age, the exception being the footballpool which has undoubtedly ebbed. Poolsare now being provided on the roofs of

The in'ormation 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, "Hbw to Patent an Invention.'

houses. This would not have been practic-able in the Victorian era, when roofs sloped

.like the shoulders of the ladies. One objectof this design was to accelerate the speed ofthe rain en route to the gutter.

Modern architects favour a flat roof, andthis makes possible the construction of aroof capable of holding water for the pur-pose of insulation. It has been found that aroof -pool reduces the temperature in upperstoreys in Summer, as much as 10 degrees.I learn that in the case of air-conditionedbuildings, a roof -pool renders it unnece.saryto dispose of the water when it has circulatedthrough the system. It can be pumped 'tothe roof, freed from its absorbed heat, andused over and over again.

A pool on the roof can perform more thanone role. In addition to acting as a refrigera-tor, it can furnish an opportunity forbathing or at least paddling. And it wouldcertainly cool the hot temper of an in-cendiary bomb.

Who's -There ?IN the bad old times, in some prison-

perchance the Bastille -a guard wasrequired without ceasing literally to keep aneye upon a certain prisoner. Through asmall hole pierced in the wall of his cell, theprisoner saw the eye of the sentry perpetu-ally fixed on him. A somewhat similaraperture is part of a newly -devised door -knocker, intended, however, only foroccasional glances. It is an inconspicuousLilliputian window of one-way glass. Theperson behind the door can see out, but theone outside cannot see in. This tiny quizz-ing glass will permit the occupant of a houseto inspect a caller before opening the door.And his-or more probably her-regard willnot be apparent to an unwelcome visitor.

" Milk -0 ! "FIBRE milk bottles fitted with a sanitary

non -spill spout and an airtight seal are nowbeing produced by a New York firm at therate of fifty per minute. A sprightlymachine shapes a spruce or pine blank intoa round container, with spouted top,

sterilizes it with hot paraffin, chills it, fills itwith milk, seals the cap, stamps the dateand dispatches the bottle to the coldstorage room, all in one continuous series ofoperations. The housewife lifts a clip,presses the edges and the spout opens. Trulya very convenient milky way.

Shield on WheelsTHE evolution of the shield is an interest -

ing study. It is stated that the shieldwas developed from the parrying stick. Thegradual widening of the stick or club in thecentre eventually expanded into the broadshield formed to cover the body from thethrusts and missiles of an assailant.

The warlike progenitors of Signor Musso-lini-the Roman legions-when besieginga city, advanced with shields held abovetheir heads and so locked as to make acontinuous cover. This conglomerateshield was known as Testudo, which isLatin for a tortoise-a creature who in-variably carries a horizontal shield.

There has just been patented in Americaa mobile- shield. This has a curbed frontand top portion and there are parallel sides.In the front there is an opening throughwhich the protected one can warily inspecthis opponent.. The contraption runs uponwheels.

Easing The Burden

PARCEL-CARRYING is something of an

art. Equally distributed weight makesthe load less burdensome. A new load -bearing apparatus has made its advent.This consists of a stout but not heavy metalframe to attach to the back. It leaves com-plete freedom to the chest, sides and waist.A load -supporting arrangement is securedto the frame by means of belts and buckles.

This device should make the heavy load,if not light, seem not so weighty. Thedonkey with well-balanced panniers findshis work not so arduous as when he carriesa lopsided pack.

Balls v. BombsUNLESS the present conflict happily

proves to be a war that ends war, dis-putes between nations will continue to besettled by the arbitrament of the bomb.As a consequence; an air-raid shelter will beas necessary to a house as a bathroom.Owing to the ingenuity of our inventors,this sanctum of security will advancetowards perfection.

An interesting development of the air-raid shelter is the subject of an applicationaccepted by the British Patent Office,According to this invention, upon two ormore thicknesses of concrete beams, thereare placed a series of concrete balls. Theidea of using balls in this way is not new.It has already been proposed to use metalballs of small diameter. But the chara-acteristic of the improved invention is thatthey are free to be moved.

The balls are arranged in layers and, asthe heap rises, the -number in each layer isdec-eased unt'l the top ball surmounts fourbills. Thus a pyramid is formed.

If the shelter be struck, and any ball ishit centrally and smashed, the other ballswill roll away. The force of the impact, willbe spread on all the balls beneath it, so thatits action will be dissipated.


a.

Three stages in thedevelopment of the bridge

The Development of the BridgeWorld Famous Bridges and How they were Built

THE first man who ever fell off a loginto a swiftly moving stream musthave been struck with the notion that

there were better methods of effecting acrossing. But he knew of none. As hescrambled out of the water and shook him-self his immediate problem presented itselfagain-how to get to the opposite bank,apart from swimming. Instinctively helooked around for another fallen log, onet hat would serve him better this time as aferry -boat. The savage had yet to developa log as a bridge.

When at last it occurred to him that hisproblem would be solved if he could spanthe stream with a tree -trunk, he was on theway to taking the first practical step thathas lead, through many centuries of boldexperiment, of heart -breaking failures andsuperb triumphs, to bridge -building as weknow it to -day. That savage who took thetoss prevailed upon his family and neigh-bours to worry a tree from its insecure root -hold in the muddy bank and "throw" it sothat it crashed its topmost branches on theopposite bank. Thus -wise did he get hisbridge. The next development came whento get the affair well clear of the water, theyraised the ends on heaped stones or soil-and chopped away the branches and flat-tened the top side.

A Bridge From TreesThen they tried to span the stream at a

wider part, and found their fallen trees tooshort. We don't know how long it tookthem to puzzle that one out, but the upshotof their deliberations and experiments was afine achievement. They felled two treesthat chanced to face each other with the

stream between, so that the topmostbranches intermingled, forming an uncom-fortable and highly precarious runway frombank to bank. It served, but they ack-nowledged how much room they had leftthemselves for improvement. In due coursethey manhandled a third tree so that thisrested among the end branches of numbersone and two. Came the day when tools andingenuity had both improved, and theyfixed a length of tree -trunk in each bank and

THE WORLD'S LARGEST ANDLONGEST BRIDGES

LONGEST: The Storstrom Bridge. Denmark -2 miles long

LARGEST: Sydney Harbour Bridge, Australia

inclined to the centre of the stream. Theyrested one long trunk on the two inclinedtops-and that was the beginning of thecantilever system of bridge -building.

The Forth Bridge, at Queensferry, Scot-land, is an example of cantilever construc-tion. Here a number of "brackets" projectout over the water and support the mainstretch of level bridge. Its total length is8,295 feet, of which 5,349 feet are coveredby the cantilever structures. The two largestspans measure 1,700 feet. The centre space,for the convenience of shipping, is 150 feetabove high-water level and its summit361 feet-only five feet less than theextreme height of St. Paul's Cathedral.There are 51,000 tons of steel in the super-structure, 6,500,000 rivets were used, andat one time 3,500 men were at work on theconstruction. They tested the bridge

finally by running two trains to and fro overit, each 1,000 feet long and weighing 1,800tons. It was constructed by Sir WilliamAn-ol & Co.. of Glasgow. and cost £3.000,001.

Rope BridgesThe rope bridge, of native India and else-

where, has its ends tied around rocks ortrees on opposite banks. At first the nativeworked his way along, hand over hand, hisbody dangling perilously over the water.Then there was devised an arrangement ofpulleys whereby he was pulled across seatedi al a piece of planking suspended from themain rope. improvement came when a caror spacious platform took the place of theplank seat. The modern transporter bridgeprobably grew out of that ; the first was inuse about 47 years ago, in the vicinity ofBilbao. A British example is the NewportTransporter Bridge, whose travelling plat-form carries 100 passengers and six vehiclesand is 40 feet long and 30 feet wide. Itcrosses the River Usk in about threeminutes, a driver operating the startingand stopping mechanism. The platform issuspended at the ends of. 20 iron ropesattached to a trolley which runs underelectric power on a rail track overhead.Construction costs of this bridge amountedto £100,000.

Suspension BridgeA natural sequence of the crude rope

bridge was the suspension type bridge.Telford led the way with these. Building hissuspension bridge over the Menai Strait (itwas opened for traffic in 1825) he had nodata to work upon, but he had full relianceupon his own skill as an engineer. He


calculated that to hold up his roadway hewould want main chains each weighingmore than 23 tons, tested to breaking -point of 90 tons each. There were to besixteen of them, and one of the severalproblems that caused him to perspire atnights when he should have been asleepwas how to get these chains over the topsof the seven piers that were to help take thestrain of the structure. He did it with theaid of a 450 -feet raft, and capstans.

A somewhat similar problem confrontedthe builders of the Victoria Falls Bridge,over the River Zambesi, South Africa.Somehow they had to get a cable across thatwide and deep gorge, and they did it byfiring a rocket across. Attached to therocket's tail was a cord, and to the end ofthat was secured a wire which was linkedwith the cable. When the fired rocketlanded on the other side men hauled thecord, wire and cable in-and the first bigobstacle was overcome. But theirs was nota suspension bridge, it was built on thecantilever principle.

Conway Suspension BridgeTelford achieved another triumph with

the Conway Suspension Bridge, and there-after there came a succession of big jumps in

(Inse11 The Indian ropybridge which finallydeveloped into themodern transporter

bridk down blow.

dimensions. A bold experiment was em-barked on in America with the building ofthe Brooklyn Suspension Bridge over theEast River, to connect Brooklyn with NewYork. Because of the unknown factors, itsconstruction occupied thirteen years. Theweaving of the suspension cables alone tookyears, and in manipulating the continuousstrands of wire they learned a very greatdeal about the effects resulting from changesof temperature. That part of the bridgewhich actually crosses the river is 1,600 feetlong; from the cable -anchorages on eithershore is 3,572 feet. The stone towers, 350feet high, were topped with steel saddlesmounted on rollers to allow of movement inthe cables which rested on them, thismovement being due to temperature

Sydney Harbour Bridge which is the largest bridge in the world

changes, sudden unequal distributions oftraffic weight, and so on.

Each of the four Brooklyn cables,15f inches thick and with a breaking strainof 12,000 tons, was composed of 5,296separate steel wires; total length of wireused was 14,000 miles. In modern practice,suspension cable wires are laid side by side,with steel bands to compress them at regularintervals. A coating of red lead is then ap-plied, after which the cable is bound withgalvanised wire and the whole water-proofed by painting. Because of thetremendous weight the cables must be builtup, wire by wire, in place-a dizzy under-taking, necessitating the slinging of steelsafety -nets below the construction.

American BridgesFarther along the East River are the Man-

hattan and Williamsburg SuspensionBridges. The Manhatten comprises eightrailway tracks, two footpaths, and a road-way for vehicles. The river span is 1,470feet, and the towers over which the 211 -inchthick cables pass are founded on masonry92 feet below high-water level ; fromextreme top to extreme bottom theirheight is 424 feet. Each cable contains9,472 wires and each cable -anchorageweighs 233,000 tons. The main span of theWilliamsburg is 1,600 feet. The tops of thetowers are 335 feet above high-water mark,and the anchorages for the cables are ofmasonry 150 feet long and wide and extend-ing upwards 100 feet above ground. Totalweight of the four cables is 5,000 tons andthey consist of 19,000 miles of wire.

A suspension bridge to cross San Fran-cisco Bay-eight miles-was visualised, andthe sum of £17,000,000 for the constructionwas not considered excessive. Goat Island,a midway rock, somewhat simplified thedesign, but the enterprise was neverthelessstaggering in its immensity. Largest span inthis bridge is 1,400 feet, with others of 500feet. Cables 29 inches thick were employed,accounting for 70,000 miles of wire. Eigh-teen thousand tons is the weight of the two


main cables, with 68,000 cubic yards ofconcrete as end anchorages. It was cal-culated that the 500 -foot steel towers wouldbe deflected at the summit by as much ast hree feet under the combined influence ofthe sun, weight of bridge -load, wind, etc.,and this extreme movement was accordinglyallowed for in the fixing of various bridge -members. The Golden Gate Bridge isanother suspension masterpiece. Taking sixlines of traffic, the roadway is suspendedfrom cables three feet in diameter, eachconsisting of 27,500 separate wires; thebreaking strain exceeds 100,000 tons. Thetowers soar 746 feet high. Total length ofthe bridge is 6.450 feet, and the longest spanis 2,400 feet.

Lattice BridgesWe got our idea of the lattice bridge from

the Britannia Bridge over the Menai Strait.This was built of straight, lengthy tubesof wrought iron supported on three stonetowers-a big departure from the use ofeast -iron. The first cast-iron bridge wasbuilt in 1779, but this material proved to beunsuitable for long spans. Iron side -girders, resembling lattice -work, followedas an improvement on the method of con-struction of the Britannia Bridge.

Pile bridges figure quite early in engineer-ing history. This system of laying downa roadway on a foundation of stakes, orpiles, driven into the river -bed may havegiven rise to the trestle bridge idea, whereinthe roadway or "deck" is raised high onstilts. Once of all -wood construction, andtherefore readily open to destruction by fire.trestle bridges are now constructed of steel.A notable example spans Van StaadensGorge. in Cape Province. South Africa : it is

642 feet long, and 254 feet high at the centretrestle. A Canadian example is the Leth-bridge Viaduct, over the Belly River; 33steel towers support the roadway which is314 feet above the water.

Swinging BridgesBridges which swing sideways, or which

allow of part of their length being turned ona pivot, to allow of larger traffic passing upand down river, are of particular interest onaccount of the constructional problemsinvolved. The Kincardine -on -Forth Bridge,opened four years ago, with a total span ofhalf a mile, has a central swing span. Whenthis is open-the swing span's extremities.pointing up and down river-there is apassage of 150 feet on either side of it. Thetotal length of this steel swing span is 364feet and it weighs 1,600 tons. It rotates on60 steel rollers each 20 inches in diameterand disposed in the form of a circular track36 feet 9 inches in diameter laid down on a42 -feet diameter pier forming a centralpivot. This pier stands on six concretecylinders bedded in solid rock and each14 feet 6 inches in diameter. The swing spanis operated by two sets of turning machineryeach powered by a 50 h.p. motor.

A movable bridge of the vertical lift typeis designed to give increased "clearance" forvessels of a larger size than normally usethose particular waters, a section of theroadway being lifted vertically. One spansthe Leeds and Liverpool Canal. In thisinstance a 20 -foot section of the roadwaycan be raised and lowered, the portion whichactually moves weighing 90 tons. Move-ment of a different kind is evident in thebascule bridges, of which type the TowerBridge. spanning the Thames at London, is

world-famous. Here the roadway, 49 feetwide, is divided across its centre, allowingthe two halves of the bascules or "leaves"-weighing 1,200 tons each-to be raised ontheir outer ends, by hydraulic power.

The arched bridge has come down to usfrom the Romans. Their arches were half -circular, whereas bridges constructed on thisprinciple in the Middle Ages had pointedarches. There are obvious disadvantageshere, the road of necessity having a verysteep rise and an equally steep fall. JohnRennie swept away the drawbacks when hedemonstrated that a bridge need only begently arched and still stand up to everyreasonable test. He was responsiblefor Waterloo, Southwark and LondonBridges.

The Storstrom BridgeAnd here are the longest, and largest.

examples. Europe's longest bridge is inDenmark-the Storstrom Bridge. It is twomiles long, contains 30,000 tons of steelmanufactured and fabricated at the Middles-brough works of Dorman Long & Co., andthe superstructure weighs 20,700 tons.Opened officially by King Christian ofDenmark in 1937, it cost £1,250,000. Thelargest steel arch span in the world holds upthe deck of Sydney Harbour Bridge. Thatarch span is 1,650 feet long and its summitis 440 feet above sea -level. The roadwaywhich it supports is 160 feet wide and 170feet above the water. With its five steelapproach spans, and concrete, towers andpylons flanking the main bridge on eitherside, it is 2f miles in length. It contains50.300 tons of steel, of which 37,000 tonsare in the colossal main span. and it costi10.000,000.

Curved Oil WellsTapping Oil Fields Under the

AS is generally known, an oil well ismade by steadily oscillating a heavydrill, which allows it to penetrate

further and further into the earth. A greatdifficulty has always been to drill a wellstraight, and a straight well is classed as onewithin 3 degrees of perpendicular. Actually,such a deviation in a six thousand feet wellmeans that the bottom can be anywherewithin an area of seven acres and mayactually penetrate some other lease or missthe underground oil supply entirely.

A young American of the name of JohnEastman devoted considerable time andingenuity to developing an instrumentwhich would drill a hole perpendicularly.He then had the brilliant idea not to becontent with orthodox drilling, but to de-liberately curve his oil wells. The apparatuswith which he does this is extremelyingenious. It consists of a long thin metalcylinder, batteries, compass, and miniaturecamera.

These are let down into the bore hole ofa well, and photograph at regular intervalsthe face of the compass and the angle of thewall of the well. The boring bit is the secondspecial part of his device. This can bedropped down the well and fixed into posi-tion -at the angle desired to drill. The anglecan be changed according to the photo-graphs taken by the underground camera.

Reaching New FieldsThe main advantage of this system is, the

huge oil fields which at present lie under thesea. Firstly, the mineral rights to the three-mile limit are controlled by the State; andsecondly, owing to the depth of water theyhave hitherto been inaccessible.

Bed of the OceanEastman sank an oil well about 200

yards from the shore. He drilled in a curvewhich went four miles under the water andthus beyond the territorial limits. His firsthole brought five thousand barrels of oila day, and incidentally, fourteen law suits,in fact, lawyers are still trying to determinewhether he is infringing the mineral rightsof the state.. Recently a still more import-ant aspect of his invention has come tolight.

Quenching Wild GushersIn Texas a well had blown up from a gas

explosion, forming a crater two hundredfeet across, boiling with oil, and throwingoff fumes as dangerous as dynamite. All theadjacent wells started to fail whilst this wellwas wasting nine thousand barrels a day,and which past experience had shown wouldcontinue until either the well was exhaustedor had burst into flame. Eastman offeredto stop this. He erected an oil derrick fourhundred feet from the crater and began toaim at the bottom of the boiling well a mileunderground. He drilled straight down for1,500 feet and then carefully calculateda slant until he estimated he was withinsix hundred feet of the bottom of the well.Water at eighteen hundred pounds pressurewas then pumped into the newly -drilledhole and the dangerous oil well was sealedwithin a few hours.

New Lease of LifeFor a world that in war or peace cannot

live without oil, the discovery of the curvedoil well might well Mean a new lease of lifeto the power machines so dependent upon it.Reproduced front "The Brook Magazine."

Counting StarsCOUNTING stars must be a very tedious

job, yet astrologers consider it a veryimportant astronomical activity. To countthe stars in the Milky Way would seem ahopeless task, but a group of astronomersendeavoured to count them down to stars ofthe fifteenth magnitude. They have nowfound a simple way to do this stupendoustask, by substituting an electric eye for thehuman eye. The surface of a sky photo-graph is scanned by a spot of light, and anelectric current is released every time astar is "discovered." Dials similar to thoseof a mileage speedometer record theresults.

A Road That VanishesMR. W. CURRAN, a Chelsea engineer,

has thought of an ingenious scheme for,making a road "disappear." The inventorhas constructed a small scale model in hisback garden and by simply pressing a but-ton, a yawning chasm will take the place ofthe road and the hole will automaticallyfill with water. With his idea a section ofthe road can be put out of action in less thana minute. A section of the road is madehydraulically, and when a button is de-pressed, drops down into 8 feet of water andthe road is flooded. Mr. Curran has alreadybeen congratulated by the Admiralty for hisideas for supplying fresh air to sunkensubmarines. In his own words he says :

can make roads and country lanes com-pletely useless to the enemy, if they evergot here, and although the cost would betremendous, I fully believe it would be worthit." He is approaching the Ministry ofHome Security with his idea.

October 1940 NEWN ES PRACTICAL MECHANICS 19

A NEW SERIES

The Story of Chemical DiscoveryNo. 3-The Decay of Alchemy

it typical chemical laboratory of the present day.

THE nonsense -doctrine of Alchemy,with its high-sounding farrago ofmeaningless and fantastic terms,

contained within itself the germs of its owndecay. For no alchemist, if he happenedto be a man of honour and of worth, couldprofess to remain intellectually satisfiedwith the endless quest after the utterlymythical " Philosophers' Stone " and the" Elixir of Life," which two entities, whenfound, were promised to provide the meansof turning all substances (particularlymetals) into gold and of enabling life to becontinued indefinitely.

The trouble, of course, was, that therewas money in alchemy. In those medievaldays of wealthy and all-powerful Princes,the desire for gain was commonly upper-most in the minds of many rulers. Hence apowerful nobleman would often retain thestanding services of a professional alchemistin order that the latter might conceivablyhit upon the much -talked -of " Philosophers'Stone " and so magnificently enrich himfor life.

The idea, quaintly enough, is prettymuch the same in our present generationwhen a manufacturing firm engages theservices of a professional research chemist,although it goes without saying that insuch an instance the underlying motive is afar more satisfying and a perfectly legiti-mate one.

" Paracelsus "One of the first rebels against the methods,

practices and beliefs of the professionalalchemists was a Swiss physician who cameto be known as " Paracelsus." AlthoughParacelsus invariably confessed himself tobe a practising alchemist as well as aphysician, he was an alchemist with hisown ideas. Indeed, he was a sort ofalchemical Hitler in his way, for he wasborn with the dictator's temperament and

natural intolerance of other people's ideas,so much so that throughout his somewhatshort life he played the role of stormypetrel wherever he went.

Paracelsus occupies such a prominentposition in the annals of alchemy that ourseries of articles would be incomplete with-out some description of his activities beingjotted down here.

By birth, Philip Hochener, the son of adoctor practising in the Swiss town' ofEinsiedeln, in which locality he was bornin 1493, Paracelsus changed his name oncommencing his professional career to" Phillipus Aureolus Theophrastus vonHohenheim." To its owner, the namesounded excellent, no doubt, but evenin those days, life was apparently con-sidered to be a little too short for "PhillipusAureolus Theophrastus von Hohenheim,"and probably on account of that fact itwas that an old Abbot of Spannheim whohad originally presided over his earlystudies, dubbed him " Paracelsus," thename being supposed to signify a " dwellerin a lofty place."

Thus did the witty Abbot feed the prideof his erstwhile pupil and, incidentally,confer upon him a name which has passeddown the centuries.

" Lived Like a Pig "Of the personality of Paracelsus there

seems to be little doubt. One old writersays of him : " He lived like a pig, lookedlike a drover, and through his glorious lifehe was generally drunk." Whilst thisassertion is rather too much exaggerated,there is no doubt that Paracelsus possessedthe Teutonic propensities of arrogance,bombast and intolerance. He generallymanaged to stir up hatred wherever he went,and at one time he had the entire medicalprofession of Europe against him.

According to Paracelsus, alchemy was

far too serious a study to be dissipated inendless searching after non-existent phant-asms such as Philosophers' Stones and thelike. All alchemists, therefore, were entirelyon the wrong track. So, too, held Paracel-sus, were the doctors. With their vegetablepotions, decoctions and extractions theywere doing more harm than good, need-lessly allowing their patients to die, when,by the application of a little intelligenceand method many such lives could besaved.

Paracelsus seems to have begun hisprofessional career by being elected to thepost of Professor of Physic (Medicine) atBasle University. Here he at once madehimself unpopular by publicly burningall the works of the older physicians such asAvicenna and Galen. In place of theirsystem of doubtful remedies, Paracelsusoffered various chemical salts which hehad discovered and prepared in his labora-tory. He used compounds Of mercury aspurgatives, iron salts as tonics, and pre-parations of lead for certain other bodilyailments. The use of opium as a pain -killerwas introduced by Paracelsus. Medicine,he asserted, was but a brand of chemistry,and he believed that the restoration of aman to health was nothing more than arestoration of the normal chemical equi-librium of his body which, of course, is aperfectly true fact.Discovery of Hydrogen

Paracelsus discovered hydrogen, havingmade this gas by acting upon iron filingswith spirit of vitriol (sulphuric acid). Hoknew that the gas was inflammable, but itseemed to be of no practical importanceto him and for this reason the real natureof hydrogen lay undiscovered until itselucidation by the English chemist, HenryCavendish, in 1766.

Despite the unpopularity of Paracelsus'spractices in medicine, his name readilygathered a certain amount of renown.A rich ecclesiastic, it is said, fell ill andoffered a hundred florins to any physicianwho would cure him. Several tried, but allfailed. At last, Paracelsus came along,gave the ecclesiastic a course of chemicalpills and eventually restored him to health.whereupon, the ecclesiastic at once repudi-ated his offer of a hundred florins for thealleviation of his complaint. Paracelsustook the matter to law, but the verdicthe received was that the ecclesiastic shouldpay him only his customary fee andnot the hundred florins which was promised.

Due to this unfair judgment, Paracelsusgave up his post as Professor of Medicine inBasle and went to Strasburg. Here hesettled for a time. Then he went to Hungaryand finally wandered all over Europe inrestless discontent, preaching to all phy-sicians and alchemists his revolutionarychemical doctrines until, eventually, heproceeded to Salzburg, where he died, moreor less in poverty, in 1541, and at thecomparatively early age of forty-eight years.

Weird NotionsThe importance of Paracelsus in chemical

or rather, in alchemical affairs, does notcentre around his strange and curiously


romantic personality. It derives from thefact that ParacelsuS rebelled successfullyagainst many of the weird and non-sensical notions of the alchemists of his day.

Paracelsus- had his own idea of theconstitution of matter. All things, he said,were made out of three components-salt,mercury, and sulphur. By combining thesethings in various proportions and bydevious ways you ought to be able toproduce any material thing of the Universe.

But this fanciful explanation of theconstitution of material things did notplease Paracelsus for very long. Soon, wefind him asserting that by the term " salt "he really means the " principle of saltness,"and so on. Thus the " three elements "of Paracelsus ultimately became threeprinciples. And here, he gave up hisconjectures in the realm of material con-stitution. The subject was too deep, evenfor his own powerful imagination.

The most famous alchemist in the periodimmediately preceding the demise of thissadly -distorted system of knowledge was aphysician of Brussels, John Baptist vanHelmont, by name, who was born in thatcity in 1577. Of a rich family, he wasintended for a Court career, but he pre-ferred the seclusion of laboratory work to the glamours of palatial apartments.Accordingly, he devoted the whole of histime to studies in alchemy and medicine, andeventually he became an enthusiastic anddevoted disciple of Paracelsian doctrines.

" Last of the Alchemists"van Helmont is called The Last of the

Alchemists." -It is a true title for the man.since it was he who first seriously began torecord certain chemical facts which hehad learned by dint of actual experiment.

van Helmont shines as the discoverer ofcarbon dioxide or carbonic acid gas.Naturally, he did not give it that name. Hecalled it gas sylvestre and referred to it asbeing a wild, untamable thing, whichexists in out-of-the-way places."

Here van Helmont introduces a veryimportant conception into dawning chemicalscience, to wit that of a material thing whichcannot be seen-a gas, in fact. Indeed.van Helmont's name goes down in theannals of chemical discovery as the manwho first applied the term " gas " which hegot from the German geist; " ghost " or" spirit," to a material substance or vapourwhich cannot ordinarily be condensed to aliquid. van Helmont found his gas sylvestreat the bottom of deep caves. He mentions,also, that it can be prepared by the actionof acids on marble and he seems to haverecognised it to be identical with the gasgiven off by fermenting liquids.

Perhaps van Helmont's epithet of " wild,untamable," was not given to his carbonicacid gas without reason, for he appearsto have made attempts to generate the gasby the action of acids on marble in closedbottles. In such instances, of course, thecontainers were invariably rent asunderby the inward pressure of the generatedgas, much, it would seem, to the worthyexperimenter's astonishment and perplexity.

van Helmont also mentions a gas-gas pinque-which was evolved from dungand garden refuse and which was inflana -mable. Probably this was an impure formof hydrogen mixed with ammonia.

Phenomenon of FlameAnother scientific fact which this Brussels

alchemist brought to light was that if ametal, such as lead or copper; is dissolvedin an acid, it is possible to recover themetal from the solution of its salt byappropriate means. van Helmont offered

no explanation of this. Had he attemptedsuch he might have been led to the elucida-tion of that great mystery, the phenomenonof flame and combustion, which so greatlyoccupied the attentions of the early scienceworkers after his time.

There is no doubt that van Helmont

Pa?-acelsus, the great alchemical reformer.

went wrong through overdoing the gassylvestre business. So fascinated was heby the " wild, untamable " properties ofcarbon dioxide that he tended to call everygas which he hit upon, " gas sylvestre."Thus it was that confusion arose in hismind about the properties of differentgases, which confusion greatly affected hiswritings.

van Helmont reduced the " threeelements " of Paracelsus to two elements-air and water. All things, he was inclinedto say, originated from air and water. To

proVe his contention in one actual case andto demonstrate that water was a primaryconstituent of all forms of matter, he put a5-1b. willow sapling into an earthenware potcontaining 200 lb. of dried earth. Hewatered the pot assiduously for five years.'During this time the willow graduallyeffected its normal growth and at the end offive years it was found to weigh a littlemore than 169 lb., whilst the earth had lostbut 2 oz. in weight.

Where, therefore, had the new willowmaterial come from ? Obviously, assertedvan Helmont, it had come from the water,which, In the willow substance, had changedfrom a liquid to a solid.

Plant RespirationHad van Helmont been familiar with the

mechanism of plant respiration, he wouldhave known that his " proof " was entirelyfallacious, since the willow had increased itssubstance by absorbing into itself carbondioxide gas from the atmosphere andbuilding this up, in conjunction with waterextracted from its soil, into fresh plant,stem and leaf material.

Towards the end of his days, vanHelmont, ever quiet and placid, appears tohave taken to deep religious meditation.He retired entirely from his former pursuitsand we hear little further about him untilhis death, which occurred in 1644.

With the passing of van Helmont thealchemical spell which had persisted sotenaciously throughout the centuries seemsto have worked itself almost entirely out.Meh were rising up in Britain who wereperceiving the first truths concerning theinteractions of material things. They werepatiently evolving systems of experimentand equally patiently recording and inter-preting the results of their experiments.

When The Last of the Alchemists "died in the person of John Baptist vanHelmont the famous Robert Boyle, ofEngland, " Chemistry's First Pioneer," wasrising into maturity. The black night ofAlchemy had departed and the firstglimmerings of Chemistry's dawn werealready clearly discernible.

THE TELEPRINTER KEEPS WAR SECRETSA Method of Secret Communication

VITAL messages pass daily and nightlybetween Headquarters and stations ofthe R.A.F. by means of the teleprinter.

The great advantage of the teleprinter inthis work of protecting Britain againstair attack is its speed and secrecy.

In appearance the teleprinter keyboard islike the ordinary three -bank typewriter, butthere are important differences between thetwo machines.

Automatic SignalsTeleprinter messages. or signals as they

are called in the Royal Air Force, are auto-matically typed by the receiving set.Stations hundreds of miles apart are con-nected by cables and when a signal is trans-mitted the depression of the key sets upa number of electrical impulses which causethe character required to be printedsimultaneously on the paper of both thetransmitting and receiving machines. Bythis means speedy transmission of news isensured. All that is needed is for anoperator to detach the copy from thereceiving set.

Unlike a typewriter, a teleprinter has noback -spacing key. Another difference is

that the result of the key depression does notappear until another key is depressed. Forinstance, in the word "the" the letter "t" isnot actually printed until the key for theletter "h" is depressed.

Secret CommunicationThe teleprinter is of great value as it

provides the Royal Air Force with a meansof secret communication. It is impossiblefor the enemy to intercept signals becauseof the manner in which the connecting linesare laid, and even if it were possible for thelines to be tapped, decoding of the electricalimpulses would be extremely difficult. Noother means of communication is so rigidlywater -tight.

When the R.A.F. first introduced theteleprinter system into its signallingorganisation the normal procedure was forthe machine to be operated by wirelessoperators, but as time went on this wasfound to be impracticable. .They could notalways be spared for teleprinting and nowteleprinter operators have to undergospecial training. Articles entitled "The Tele-printer-How It Works" appeared in the Juneand July issues of "Practical Mechanics."


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American naval architects. The ships willhave curved armour -covered decks and pill-box gun batteries. The whale -back deckwould completely cover all parts of the shipnow exposed to fire, including the bridgeand communications system.

A " Parachute" CabinLONG before Hitler thought of using

parachute troops in modern warfare,Robert M. Thomson, a 41 -year -old Miamiinventor, perfected an armoured cabin tolower fighting men from an aeroplane.Invented in 1928, and patented in 1933,Thomson has been trying to get the UnitedStates to adopt his idea. The bullet-proofcabin fits inside the belly of a large plane, isreleased by the pilot, and floats to theground by parachute, while the 20 meninside fight off ground snipers with machineguns, rifles, and hand grenades. AlthoughThomson thought of the idea 12 years ago,recent war developments have brought hisparachute invention to the fore. TheAmerican War Department is consideringthe merits of the invention.

Harold F. Pitcairn, president of the Pitcairn Autogiro Corporation with his newPA -36 autogiro. Mr. Pitcairn is shown pointing out the location of the new typemotor used in the 'giro. It is located in the middle of the fuselage. This gives greatervisibility over the front cowling. The autogiro is capable of rising vertically, making itindependent of ground obstacles or conditions of terrain. Army and navy officials

inspected the craft, but have kept their findings a secret.

Britain's Secret WeaponTHE terrific losses that Britain is

inflicting on the German air force iscausing considerable comment in America,and mention is made of a newand terrifying British weapon." OneAmerican newspaper says : England'ssecret weapon, a spiderweb of steel cablesfired from guns, has been tried out in Naziair raids on the South -East Coast.

" Cables were shot from what are calledrattling guns.' The guns belched forth

great balls of cable, which opened out overthe sea into steel screens dangling from

miniature para -chutes. Throughthe steel netslermans were seen

descending by para-chutes, trying to

void the whippingtentacles of thecable curtain."

ImprovingStainless SteelSCIENTISTS at

MassachusettsInstitute of Tech-nology have dis-covered that byadding tiny tracesof silver to the com-position of stainlesssteel, the latter canwithstand the cor-rosive action of saltwater. Only an in-finitesimal amountof silver is required.

emierimented with in the United StatesArmy.

More Power for the WellingtonsBR1T1SH " Wellingtons "-the famous

1.) long-range bombers of the R.A.F., havenow been given an even finer performancewith new -type engines. Two liquid -cooledRolls-Royce Merlins "-the type fittedin the famous Hurricane and Spitfirefighters-replace the radial air-cooled typespreviously fitted. Whilst the improvedperformance figures are secret the severalhundred extra horsepower may be assumedto add considerably to the former speed ofaround 260 m.p.h.

Seventy -ton TanksTHE United States Army have decided

to embark on the construction of monstertanks, weighing 70 tons and mounting3 -in. guns.

Whale -back Ships"WHALE -BACK " ships for defeating

air bombers are being considered by

THE MONTHSCIENCE ANDA MysteriousDevice

R. R. BACK -HOUSE, of

Wombwell, a 35 -year -old motorengineer, has in-vented a gadget forimmobilising motorvehicles which, heclaims, will bafflethe Nazis. More-

over, he declares that when his devicehas been applied no motor expert in thecountry can start a car in less than halfan hour, or even find what the "trouble"is. The ignition key is not removed and therotor arm remains in position. Mr. Back -house states that his device costs less thanhalf a crown and can be applied in a fewseconds, and so easily that a doctor coulduse it without soiling his hands.

Long -Range Tanks'TANKS with oil -burning diesel engines.

1 giving them double the range in whichto strike without refuelling, are being

One of the famous long-range bombers of the R.A.F., the fricke-s "Wellington- which has now been fitted with Rolls Royce Merlin engines.


A Robot TorpedoMR. J. R. FISI4, a 45 -year -old American

research engineer, has perfected asound -directed robot torpedo. The torpedois directed to the ship by sound comingfrom the ship to be hit. Fish is also workingon a robot rocket for bringing down planeswhich will operate on the same principle.

From Top to ToeACCORDING to an Italian newspaper,

the women of Germany are now beinginvited to give up their hair so that it canbe used to make socks and clothes for thetroops. In the Thuringia district, it isstated, women provided 400 tons of hair.

Steam PlanesCCORDING to a report from Washing-

rA ton, successful experiments are beingcarried out with a new type of aeroplaneengine which is steam -powered. It isclaimed that both engines and aeroplanescan be built much more rapidly than anyof the types now in use. So fast is produc-

with small lighting buoys designed forcarrying on a raft, and with battery lightsfor fastening on their clothing, as part ofits compulsory equipment.

Tiny Robot PlanesMR. EDWARD F. CHANDLER, a well-

known American marine engineer, hasdeveloped a tiny robot plane of a new typefor defence against bombers which he calls" the flying bumblebee." The planes havebeen so designed that they steer auto-matically by the sound of the attackingbombers. They then race along overhead,dropping bombs on their victims. Mr. Chand-ler is a recognised expert in automaticsteering controls for torpedoes, aircraft,and marine vessels. In the last war he dis-tinguished himself as the inventor of agyroscopic control system for accuratelyaiming submarine torpedoes. He alsoassisted in developing the Swedish Navy'ssound -controlled torpedo. Mr. Chandlerplans a set of four sound controls whichshould lead his bumblebee to wheel intoline above a bomber and slightly ahead of

IN THE WORLD OFINVENTIONtion possible, that 60,000 planes a yearwould be quite easy. The inventor claimsfor his new unit that weight has been cutsubstantially. The wings of the plane aremade to act as water condensers, and thebugbear of ice formation is turned to goodaccount. Experiments with the new engineare now to be made at great altitudes, andif they prove successful, the Governmentwill take over the designs and arrange forproduction.

Silk -twisting MachineMR. G. R. LEWIS, of Cheshire, has

invented a machine which, for a longtime the Germans have been trying toproduce. This invention, in one continuousoperation, produces the silk -twisted cordused in house furnishing, women's garmentsand girdles from a single thread to thefinished article, measured and wrapped in acontainer.

Expanding RingsNEARLY everyone is familiar with the

expanding watch bracelet, and nowring shanks have been produced on thesame principle. It is like a miniature watchbracelet and, unlike any ordinary ring,stays neatly in position on the finger anddoes not slip sideways. It can be fitted toany existing gem -set head.

Launching Gear for RaftsAMONG the devices to help in the rescue

of shipwrecked men, which wererecently exhibited at the Ministry of Ship-ping, was a model of the T.D. stowing andlaunching gear for life -rafts, invented byMr. R. S. Chipchase, managing director ofthe Tyne Dock Engineering Company. Thespecial cradle in which the raft is housedcan be fitted to the rigging and provides forvery quick release by means of a kick. Ifthere has not been time to free the raftbefore the vessel sinks, the upward pres-sure of the water would then release it.

The merchant navy is also to be supplied

it. The controls would also tend to keepthe little plane at a predetermined distanceabove the bomber it is attacking. -When inposition it would drop its bombs.

New Aeroplane EngineMR. CHARLES A. TOCE, mechanical

engineer, of Houston, Texas, U.S.A.,has offered the United States Governmenta new aircraft engine which, he assertsdevelops twice the horse -power for the samedisplacement and with less weight than thenormal engine, which costs twice as muchas his to build. Toces y ; that the engineis the result of nine 1

years of develop- I

ment and now hasreached the point ofperfection.

Flashless Elec-tric MachineGun

/IRGIL RIGSBYV of Hull, Texas,has invented a flasli -less electric machinegun which mayshortly be madeavailable to the

A view of the installa-tion of the world'smightiest X-ray machinein the new high -voltagelaboratory of the U.S.Bureau of Standards inWashington. TheGeneral Electric Com-pany is constructing the1.400,000 -colt machinethat will supply X-radiation equivalent to

that of $150,000,000worth of radium. The32 -foot columns in centreform the generating unit

of the machine

United States Army. A Pittsburgh manu-facturing company have offered to supplythe weapon and attempt to perfect it. Thegun, although only in the experimentalstage, has a muzzle velocity of 400 ft. asecond.

Mr. B. D. Atwell, engineer of the Pitts-burgh firm's plant, said that the principle ofthe gun is sound, but " it will take a muchhigher muzzle velocity to make a warweapon of the gun." The bullets are jerkedthrough the gun by means of magneticcoils, which may be operated from batteriesor from a power line. The big advantagewith this type of gun is that concealedtroops could silently operate against theenemy, who would find it difficult to spotthe machine gunners.

Planes Produced by PhotographyPHOTOGRAPHY plays an important

part in the mass production of planes atthe Glenn L. Martin plant at Baltimore,Maryland. A huge camera is used which iscapable of reproducing engineering draw-ings on any kind of surface. Time andmoney in redrafting is saved by this method,and, it is also claimed, speeds up production.

Pithead Winding GearCOLLIERY managers and engineers

were recently present at a demonstra-tion of a new type of mobile pitheadwinding gear. The machine is consideredone of the most remarkable of recentinventions, and is for use at any pit in theCannock Chase, Warwickshire, or Shrop-shire area in the event of the ordinary gearbeing damaged by air raids or other enemyaction. It weighs 24 tons, is 12 ft. high, andcosts some thousands of pounds. Themachine is mounted on six huge pneumatictyres, and it can travel along roads drawnby its special lorry, or the road wheels canbe taken off to enable it to be placed on arailway line. Fitted with. every safetydevice attached to the most modernwinding gear, it is primarily for use followingdamage from air attacks, but it can alsobe used in any emergency.

24 NEVVN ES PRACTICAL MECHANICS October, 1940

Testing Magnetic Materials

Fig. I.-Apparatus for testing magnetic materials.

THE basic characteristics of magneticmaterials may be determined for themost part from the. various relationships

between the flux density and the magnetis-ing force. These relationships are repre-sented graphically by a magnetisationcurve, and a series of hysteresis loops.magnetisation curve represents the relation-ship between flux density, B, and magnetis-ing force, H, as the latter is increased fromzero up to such a value that further increaseproduces no appreciable increase in flux.The hysteresis loops represent a completecycle of flux change as the magnetising forceis decreased from some value H1 to zero.then reversed to a value HI, and thenincreased to the original positive value.The areas of these loops represent the mag-netic losses in the material over such a cyclewhen the change in magnetising force ismade slowly.

pleasuring FluxA large part of the Magnetic materials

testing consists in determining these curvesfor the various materials used in the BellSystem, but since these materials, varywidely not only in magnetic characteristics,but in the form or shape in which they areobtained, no single procedure can be appliedto all of them. In general the flux is meas-ured by placing a winding on a sample of thematerial and measuring the quantity ofelectricity caused to flow through thiscoil when a change is made in the magnetis-ing force. The determination of magnetis-ing force, however, is not always so easy.1Vhen the material can be formed into a ringof uniform cross-section, it iudetermined byplacing a winding of a known number ofturns on the ring and passing a measuredcurrent through it. This gives the magneto -motive force in ampere turns, which may beconverted to the magnetising force bydividing by the length of the magneticpath. This is the simplest and most satis-factory method, and is always used whenpossible. Where large numbers of Similarsize samples are to be measured. special jigs

Elect() MechanicalApparatus

be approximated in one of several ways.Where the material is a straight rod of suchphysical characteristics that it can be bent,it may be formed into a ring and then weldedby one of several methods that are knownnot to have a harmful effect on the material.Where this bending is not desirable, theequivalent of a ring may be formed bymilling a narrow slot lengthwise down therod and then spreading the sides to forma link. Coils may then be placed around thetwo sides of the link. Both of these methodsgive the magnetic properties in the directionof drawing. At right angles to this direction,however, the magnetic properties areoccasionally different, and to determinethem the rod may be drilled out to forma bushing, which may then be tested asa simple ring. Typical specimens of thistype are shown in Fig. 3.

Thin SheetsMagnetic material frequently comes in the

form of thin sheets, and these may beformed into the equivalent Kif rings in

Fig. 2.-Clamping a specimen in a Fahy Simplex permeameter

are employed to avoid the necessity ofplacing separate windings over each. Thismethod is particularly suitabk for measure-ments on toroidal cores, such as are corn-s nooty used for loading coils and for certainbums of transformers or repeating coils.

Type of SpecimenIn other cases, this 4vpe of specimen can

Fig. 3.- Typical specimens of magnetic materials modefrom hors.

several ways. Such sheets also occasionallyhave different characteristics in differentdirections. Where the characteristics are tobe determined in one direction, the materialmay be cut into a narrow strip and thenwound into a coil consisting of a number oflayers, over which a winding is placed.Where the material is very thin, the tape isoften wound on a spool of refractorymaterial, which serves as a support duringheat treatment and test. With material ofsuch a nature that the pressure of a windingmight change the magnetic characteristics,the wound tape is placed in a toroidal boxwhich serves as a support and protection forthe coil. Sometimes the sheet, due to itscrystalline structure, has two directions inwhich the magnetic characteristics are thesame, but different from those in other direc-tions. Under these conditions hollowparallelograms are cut from the material toform a core. Specimens of sheet materialsin various forms are shown in Fig. 4.

Some materials, such as the steels used forpermanent magnets, are too hard mechanic-


ally to be treated in any of these manners.and must be tested in their rod or bar form.Several types of d -c permeameters are avail-able for such tests. They consist primarilyof yokes of high permeability and largecross-section to complete the magneticcircuit of the bar specimen, and coils forcreating the magnetising force. Althoughthere is a closed magnetic circuit carryingthe same flux throughout, as when a ringspecimen is used, the determination of themagnetising force in the specimen is not sosimply obtained because of the differencebetween the magnetic material of the yokeand of the specimen.

Magneto -Motive ForceThe magneto -motive lbrce divides itself

across the various sections of a magneticcircuit in direct proportion to their lengthand in inverse proportion to their cross-section and permeability. Since bothpermeability and magnetising force varyover different sections of the magneticcircuit, the correct values for any one sec-tion cannot be determined with sufficientaccuracy from the total magneto -motiveforce and total flux. The magnetising forcemust be found, therefore, by other means.and is determined differently with the twotypes of permeameters described below.

With the Fahy Simplex permeameter,shown in the foreground, Fig. 2, the yokeis U-shaped and the entire magneto -motiveforce is supplied by a winding on thebase of the yoke. With this arrangement themagneto -motive force acting on the speci-men is determined from the flux through anair -core coil bridged across two high -permeability posts in contact with the endsof the specimen.

Babbitt PermeameterWith the Babbitt permeameter, shown in

the photograph at the head of this article,the magneto -motive force is supplied by twowindings connected in parallel electrically.One is on the U-shaped yoke and the otheracross the sides of the U, and the specimen Is

1.4

12tn

0-J 1.0

0'Jtt0.6wwUn

r2 0.6

0.4

:21 0.2

02 4

FLUX

0.026-2 5%Si STEEL

Si STEEL

45%LLOY

6 8 0 I2 14 16

DENSITY IN KILOGAUSSE5

Fig. 5. - Core losses in typical materials determinedwith an Epstein testing set.

Fig. 4.- Typical specimens made from sheet material

placed inside this latter-coil. These twowindings are proportioned so that the oneon the yoke produces' just sufficient mag-neto -motive force to maintain the fluxthrough the yoke while that around thespecimen maintains sufficient magneto -motive fOree to maintain the same flux.

that applied to the specimen, and smallchanges in it are negligible.

A.C. and D.C. FieidsThe properties of magnetic materials

under the influence of A.C. fields differ fromthe D.C. characteristics, and for lowmagnetisng forces are determined for themost part by bridge measurements of theinductance and resistance of a windingplaced on them, as already described. Forsheet material used in power transformers,however, the sixty -cycle loss at high fluxdensities is of particular importance, and ismeasured with an Epstein testing set shownin Fig. 6. Strips of the specimen sheet areplaced inside four coils forming a hollowsquare, and the coils-connected in series --are supplied from an A.C. source througha wattmeter. The reading of a voltmeterconnected across a secondary winding withthe same number of turns as the primary isa measure of the flux, and the loss is ob-tained from the wattmeter reading. The

Fig. 6.-An Epstein testing set employs primary and secondary windings on a rectangular core made upof specimen strips.

With this arrangement the magneto -motiveforce in the specimen can be calculated fromthe current flowing in its exciting winding,and the flux is determined from an auxiliarywinding placed over the specimen. Theratio between the two exciting windingsshould theoretically be varied for eachchange of specimen, but since these per-meameters are used only for low -permeabil-ity materials, while the yoke is of very highpermeability, the magneto -motive forceapplied to the yoke is only a small part of

losses of typical materials are shown in Fig. 5.Because of the very extensive use of

magnetic materials in the telephone plant,almost every known magnetic property isutilised. Not only must a very greatvariety of materials and shapes be tested,but a wide variety of types of tests is alsorequired. Those described above, of course,are only a few, but they are representativeand give an indication of the types of teststhat, must be made. (Reproditced front BellLaboratories Record.)

"Everyday Science," by A. W. liaslett.Published by The Scientific Book Club.266 pages. Price 2s. 6d. to members.NOWADAYS it is evident that science

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BOOKS RECEIVEDSee also pages 14 and 31

against disease and insects. Further, in therealm of the engineer there is the importantproblem of waste, and our inability to usenature's riches .to the full. The book iswritten in non -technical language, andmakes an informative tour of everydaytopics which are of interest to everyone.

Stamps of the WorldWE have just received a copy of

the standard catalogue of Postage

Stamps of the world (1941 edition), pub-lished by Whitfield King & Co., Ipswich.Although the number of copies printed hashad to be considerably reduced, the size ofthe volume and number of illustrations areincreased as compared with last year, andthere are now nearly 1,000 pages and morethan 7,800 illustrations. There has been noalteration in quality or curtailment of theusual features.

This catalogue lists and describes everyissue of the world's postage stamps since1840, known at the time of going to press,and the information as to prices, geographi-cal data, etc., is based on the latest avail -a hie information. It costs 6s. tid.


An Ingenious

CUTTINGSHEARS FOR

ROD CUTTING SHEARSMETAL

BENDINGDIE FOR

METAL -BENDINGJIG FOR

VICE TO HOLD RODFOR SCREW CUTTING

GAUGE BAR

PUNCH FORPERFORATING METAL

Fig 1.-Showing hew six separate tools are incorporated inthe Juneero Tool.

MODEL making is always a fascinat-ing hobby, and provided one hassuitable tools the task is con-

siderably simplified. But when tools andmaterials are not available, models are aptto take so long to produce and to cost somuch that many would-be model makersare forced to give up their hobby. A tool isnow on the market, however, known asthe Juneero Multi -Purpose Tool which issold complete with model -making materials.With the tool it is possible to construct andfinish an almost endless variety of articles.from complete working models to a host ofpractical and useful things for the home.garden, garage, and workshop. Juneerois sold in two sets-No. 1 costing 15s., andNo. 2, 30s. There is also the workshop setat 60s. The Juneero tool is the same inboth sets, but No. 2 is more comprehensiveand includes a scroll tool and shears, aswell as more materials, enabling advancedwork to be undertaken. It also contains

Fig. 4.-Cutting strip.

mult-Purposo ToolMetal Working and Model -Making at Small Cost

metal strips and rods and acutting die for cutting threadson the rods. Ruled metal sheetswhich simplify cutting are alsoincluded as well as corrugatedmetal, metal discs of varioussizes, glass substitute, spanners,nuts and bolts, and a penknifewhich incorporates a rule andscrewdriver.

The Juneero ToolA glance at the illustration of

the Juneero tool shows that sixseparate tools are incorporated,most of them operated by thesingle lever or handle. Thereare shears for cutting strips andat the back there are shears forcutting the rods. Below theshears is a punch for perforatingthe strips with perfectly round,clean-cut holes for the bolts. Atthe back of the tool is theforming die in which the stripscan be bent to any desiredangle and below the hole inwhich round bars are held to bendthem. The tool is also provided

with a gripping vice for holding the rodwhen cutting screw threads on it. A wingnut locks the gauge bar in position. Withthe aid of the gauge bar parts can be mass_

Fig. 3.-Setting the gauge bar

produced with factory precision-eachexactly like its fellow.Punching Holes and Slots

The punch for the holes, which is situatedin front of the tool, is operated by pullingthe handle down gently in the mannerindicated in Fig. 2. Particularly in modelengineering work, slots are occasionallyrequired. These can be cut by punching onehole and then moving the work along insteps of ilt; in.. punching successive over-lapping half -holes. With a little practiceperfectly formed slots can be cut. To spacethe holes correctly they can be markedout with dividers or the gauge bar may beemployed. Where a number of equally -spaced holes are being cut an alternativemethod suggests itself : bend one end of alength of round bar up about in. Clampthe bar in the vice with its upset end set toindicate the space desired between succes-sive holes. Oil the punch occasionally to

r3serve its cutting edge.Cutting Strip

To cut metal strip, place the strip as faras it will go into the jaws of the tool and,by pressing the handle down, the shears willcut the strip. To ensure cutting the endsoff dead square, you will find it best tostand behind the tool and sight the stripalong the gauge bar. Fig. 4 shows how thetool is used for cutting strip The hole inwhich the rod is inserted for shearing is tobe found at the top of the back of the tool.

For some decorative work it is sometimesdesirable to cut the ends of the strip into aspear point. To do this place the strip inthe jaws from the front of the tool, holdingit at the required angle in relation to the

Fig. 2.-Punching strip

operating handle. Oil the cutting edgesoccasionally to preserve their cutting edge.The Gauge Bar

Mention has been made of the gauge bar,and this can be moved endways to anygauge. It can also be rotated in its holderto bring its end opposite the punch or eitherof the shearing or bending positions. Afterthe gauge bar has been moved into positionit is locked by tightening the wing -nut thatprojects in the front. By the use of thisbar the necessity for marking out each partis avoided and it is possible to produce asmany parts as are required, all exactly thesame as each other.

If it is desired to perform a number ofoperations en parts which must all beexactly alike, the first part of the series tobe made should be marked off and placedinto position in the tool. The gauge baris then moved to come into contact with itsend and locked in position as shown inFig. 3. After the operation has been com-pleted, each succeeding part is inserted inthe tool, in such a manner that its endcomes into contact with the gauge bar,obviating the necessity for further markingoff and ensuring absolute uniformity.

A further article describing other applica-tions of the Juneero Tool will be given nextmonth ; in the meantime readers may obtainany information regarding the tool fromJuneero Ltd., 25, White Street, Moorfields,London, E.C.2.


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2£1

THE SNEWNES PRACTICAL MECHANICS

PAR

Fig. 1.-Inspecting the chronograph chart.

TO keep a continuous check on therelative rates of the crystal clocksin America which comprise the Bell

Laboratories' frequency standard, and alsoof their absolute rates in terms of radiotime signals, a spark chronograph is used.It permits a continuous intercomparisonof the timekeepers by automatically record-ing on a slowly moving chart a curve foreach clock. These curves indicate at anypoint the difference in time between theclocks.

The record is made on waxed recordingpaper which is drawn slowly by a sprocketover a long knife -edged electrode mountedwith small clearance below a rotating drum.The drum has raised above its surface ametal spiral which just clears the paper andforms with the electrode a short spark gapwhich traverses the width of the chart oncefor each revolution of the drum. Sparksperforate the paper at positions whichdepend on the angular position of therotating drum and leave very small butreadily visible marks where the wax meltsaround the hole. The visibility of thesemarks can be varied by controlling theintensity of spark.

Successive Sparks ,

When successive sparks occur at intervalswhich correspond exactly to any wholenumber of revolutions of the spiral, theperforations lie on a straight line parallelto the direction of motion of the recordingpaper. If the sparks come earlier or later byamounts proportional to the elapsed time,the corresponding indications lie on astraight line inclined to the direction ofmotion. The slope of this line is an accuratemeasure of the rate of the clock mechanism

C HRO NOGRAof Crystal Clocks

Keeping a Continuous Check on the

which produces the sparks,relative to the rate of thechronograph drum. Thus,any mechanism that pro-duces electrical impulses atintervals simply related tothe period of the rotatingcylinder may be comparedwith it as a timekeeper.

Any accurate source ofalternating current may beused to drive the chrono-graph, and this source thenbecomes the reference stand-ard. When a crystal oscillatoror other high -frequencysource is used to control thespeed of the drum, a sub -multiple of the high frequencyis used to drive it.

" Gaining " or " Losing "The chronograph shown in

the photograph operates froma 100,000 cycle crystal oscil-lator through a frequencyconverter which gives a 100-cycle output, and is designedso that the spiral makes tworevolutions every second.The time interval correspond-ing to the entire chart widthis therefore one-half secondand the smallest divisions

represent h mdredths of a second. If therecord changes its position by five smalldivisions per day, the clock which madeit is gaining or losing five hundredths of asecond per day, relative to the rate of

PULSEINPUT

0 l'OR

RAISEDSPIRAL

GAS -TUBERELAY

00

PAPER

HIGH -VOLTAGE

ELECTRODE

TAKE-UPREEL

200VOLTS DC

GEARTRAIN

900.000-

Fig. 2.-A metal drum with a spiral raised above itssurface rotates above a moving sheet of recordingpaper, which passes over a long knife -edged electrode.Sparks from the knife edge to the spiral perforate thepaper at points which depend on the angular position

of the rotating drum.

the drum. Whether a given slope means" gaining " or " losing " depends on thedirection of rotation of the spiral. Theinstrument described here has a left-handspiral and a clockwise rotation when viewedfrom the left, so that a slope upward to theleft corresponds to a gaining rate relativeto the chronograph. The chart is movedat the rate of three inches per day bygearing from the main motor and the recordof the entire past week is kept continuouslyin view before it is wound automaticallyon the take-up reel.

20 30 40 so

October, 1940

Relative Rates

10 30 50 50

1

0 20 30 40 So

Fa 30 40 50

Fig 3.-Chronograph clart. The three records a theeft were made by hree crys al clocks. The other trace isa record of time signals received hourly by radio.

The Electrical CircuitThe electrical circuit used with the spark

chronograph permits making several clockrecords on the same chart without mutualinterference. The rate of any clock mechan-ism which produces regular electrical pulsesat intervals of a half -second, or multipliesthereof, can be measured by allowing thepulses to operate a gas -tube relay. Thecondenser in the plate circuit of the relaytube is charged slowly to about 200 voltsthrough a high resistance, and dischargedvery abruptly through the primary of aninduction coil when the operating pulsearrives. This creates a high potential inthe secondary winding which breaks downthe gap between the knife -edged electrodeand the grounded rotating spiral. Thepassage of the spark through the papermakes a permanent record on the chart and


INGENIOUS and completely PRACTICAL

EnMULTI-PURPOSE

PATENTTOOL

SEE WHAT IT DOESSHEARS metal strips

and rods toaccurate lengths (see above).

PUNCHES =et:steel strip (see left).

BENDSstrip to accur-ate right angle

or any other angle required(see right), also rods.

THREADS rods withthe aid of

Juneero screw -cutting die (seebelow).

JUNEEROSCROLL TOOLFor making accuratecurves and circleswith strip or rodquickly and easily.Fitted with thumbscrew. Included in30,- and 60,- sets, or

Price 2/6

A HUNDRED USES

IN THE WORKSHOPThis amazingly ingenious tool offers the inventor, the indus-trial designeraccurate andexplaining ordimensions is

drawings, and

WORKSHOPSET

Handsome modernchest containingcomplete set ofJuneero tools andgenerous supply ofmaterials -. plainmetal, corrugatedmetal, metal discs,rods and strips,glass substitute.springs, etc.

Price 60' -

or handyman a rapid means of constructingwell -finished models in permanent form. In

working out a new idea, a model in threeoften far more convincing and useful than

with Juneero can be made in a fraction of thetime. In addition to models theJuneero tool is

fully capable of turning outthoroughly practical small-scalearticles ready for use. InspectJuneero sets,

design sheets

and materialsat your localJuneero dealer.or send couponfor full details.

Juneero Sets are also available at 15/- and 30/-. Fresh suppliesof materials available in 1/- packets from your Juneero dealer.If, owing to war conditions, you have any difficulty in obtain-ing your set, send your remittance to us, adding 1/- forpacking and postage (Abroad 5/6 extra).

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I COUPON: Write Name & Address in Margin 21--rsi%; To JUNEERO LTD., White Street, Moorfields, London, E.C.2. ;I Please send me particulars of Juneero Sets and name of nearest Juneero Dealer.


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indicates the instant of occurrence bychronograph. time. As the chart moves,and more sparks occur in succession, thetraces form a line which is straight whenthe rates are constant.

ScatteringThe points on the record scatter some-

what because a spark does not alwayschoose the most direct path. This accountsfor most of the normal scattering whichamounts to about one and a half milli-seconds either side of the mean. Meanobservations can be made with an accuracyof better than one millisecond by measuringto a line drawn through the centre of theline that is traced.

Several gas -tube relays can be used withone induction coil so that many recordscan be made on the same chart withoutmutual interference. Fig. 3 shows a chartwith four records, of which the three at theleft are comparisons of three crystal clocksagainst a fourth which controls the chrono-graph. The fourth trace is a record of timesignals received hourly by radio. Thesomewhat greater scattering in this recordis largely due to irregularities in radioreception, such as those caused by fadingand static. The radio signal is allowedto record for one minute during eachtransmission. There is no observablemovement of the chart during a singletransmission and the record appears asgroups of points spaced hourly along thechart.

The three similar records are identifiedby the use of a simple timing device whichdeletes a small portion of each trace everytwelve hours in a pre -arranged sequence.This method can be used to label anynumber of records and does not impair thevalue of the long-time comparisons.

Precision of MeasurementThe section of chart shown includes

records for somewhat over three days andindicates relative rates accurately to some-what better than one part in thirty millionbetween the crystal clocks. Thus theprecision of measurement with the sparkchronograph can be very great although itinvolves apparatus and methods of great

which is vaporised from the paper bythe spark, condenses on the cylinderand increases somewhat the scattering ofthe record.

By increasing the speed of rotation of thecylinder or by enlarging the physicaldimensions of the recording parts, theresolution and hence the accuracy of timecomparisons can be increased considerably.

Fig. 4.-Photomicrograpas of spark records which show the perforations in the chart and the dark ringswhere the wax was melted by the spark. The divisions on the chart represent hundredths of a second.

simplicity and reliability. The only movingparts, aside from the recording paper,execute simple rotation at slow speeds. Infour years of continuous use, no operatingtrouble has developed. The only main-tenance involved, apart from infrequentoiling and changing of the chart roll, is toremove a thin layer of wax from thecylinder about once a year. This wax,

The dimensions and speed of operation ofthe Labcratories' chronograph were chosento give the best practical compromise foraccuracy, convenience of mounting, andlong life. The result is an instrument whichhas served very satisfactorily as the chiefvisual means of checking continuouslythe performance of the frequency standard.Reproduced from Bell Lohorotorie* Record. -

" Electrified Dirt "Aluminium-- the Aircraft Metal

Aluminium, sometimes described as elec-trified dirt, has suddenly become almost aprecious metal. This may seem surprising,since roughly one twelfth of the entireearth's crust consists of the elementaluminium. In fact, the world holds neartwice the amount of aluminium as of iron,the next most abundant metal.

The trouble about aluminium is that it isnever found in its metallic state. Such is itsaffinity for oxygen that it occurs princip-ally as a hydrated oxide, known as alumina.Richest of the alumina ores is the claylikesubstance bauxite. There are others, suchas gibbsite, felspar and china clay whichcontain the elusive metal. Occasionally,too, it turns up more spectacularly as aprecious stone. Turquoise, topaz, andgarnet are but phosphates and silicates ofaluminium.

BauxiteBauxite i s generously distributed through -

Out the world, more espeCially in sub-tropical and tropical areas. India, centraland west Africa, Australia, British andDutch Guinea, have vast deposits. And sohave Greece, Jugo-Slavia, Roumania and theU.S.A. Not all of it is workable, or containsa sufficiently high proportion of aluminato make its mining an economic business.Some of the best mines are in the region ofMinx, in southern France. Other goodproducers lie along the Adriatic. Since thefall of France, the actual-but not potential

----world production of bauxite has swungover in favour of the Axis powers.

Making AluminiumBut bauxite is not the only thing that

goes to make aluminium. Besides the fouror so tons of clay needed to produce asingle ton of metal, a ton of soda and otherchemicals and half a ton of carbon elec-trodes are consumed. A vast amount ofelectrical energy, too, is used in the pro -

IMPORTANT NOTICE TO ALLREADERS OF PRACTICAL.MECHANICS WHO MAY BE LEAV-

ING THEIR PRESENT ADDRESS.

If you are moving from yourpresent address into another districtit is most important to place anorder with your newsagent as soonas possible after arrival. By thismeans the copy cancelled at yourold address will be made availablein your new district, and you will beable to continue reading PracticalMechanics without interruption.Please remember TO ORDER fromyour newsagent because owing to thepaper shortage he cannot supplywithout your instructions in advance.

cess of electrolysing the alumina-thecurrent passing through the electrical fur-nace being somewhere around 10,000 to20,000 amps. For this reason aluminiumplants are best sited near rivers or falls,where cheap power is available from hydro-electric sources. Norway, Italy andAustria are all well placed in this respect.North America is also blessed with abun-dant power, hence both U.S.A. and Canadaare large producers.

Lightest of MetalsOne of the lightest of metals-it has only

half the weight of iron, little more than athird that of copper-aluminium wasdestined, from its first effective productionin 1907, to play a vital part in aircraftconstruction. In 1918, when aircraft werestill largely made of wood, about 90,000 tonsof aluminium-or half the world's output --were used in the aircraft of the Allies. Theadvent of the all -metal 'plane, and moderndevelopments in aluminium alloys and thetechnique of hardening and welding, havegreatly increased the possibilities for theuse of the flying metal.

" Calvert's Mechanici' Year Book ""THE issue of " Calverfs Mechanics' Year

1 Book for 1940" contains much usefultechnical and industrial information for themechanical, constructional, electrical, andgas engineering industries, including anumber of handy tables such as metricalequivalents of inches, weight per linealfoot of seamless drawn copper tubes,comparative table of different wire gaugesin use, and many others. The year book is pub-lished by Sherratt and Hughes, Park Road.Timperley, Altrincham, and costs sixpence,


PRACTICAL MECHANICS WIRELESS SUPPLEMENT

Fig. 1.-Neat and attractive appearance of the

finished unit.

0 NE form of radio entertainmentwhich is becoming increasinglypopular, is that of " Home Broad-

casting," this being largely attributable tothe more frequent gatherings now, roundthe fireside.

The majority of receivers making pro-vision for gramophone reproduction, affordat least two stages of L.F. amplification, andthis is normally quite suitable, assuming thecircuit conditions to be up to standard, forthe average domestic requirements in thedirection of home broadcasting.

The merits of a microphone reproduction,however, depend very considerably on theability of the " home producer " to equalisethe sound distribution of the performers inthe broadcast, with the instruments oreffects, good mixing being essentially thefactor which ultimately determines thefeasibility of say, a thriller play, or amusical item.

This consid-ration then brings one imme-diately to the question of microphone toperformer distance, the word performer, ofcourse, being literally applicable to theeffects side. For good dramatisation wherethe actions and positions of the performersare to be unrestricted, and even with thebest microphones obtainable, it is practicallyessential for an " easy running " repro-duction to provide some degree of pre -amplification where not more than twostages of receiver amplification is in evidence.

It is along these lines that we havecarried out some interesting but quite simpleexperiments to ascertain the better way ofmeeting the requirements just mentioned.

An Amplifier andMixer Unit

Combined Pre -Amplifier and Mixer UnitConstructional Details of a Compact Unit

for Home Broadcast Useand with no mean viewo the question of ex-

pense. The serviceable-ness of a pre -amplifiercalled for the combinedadvantage of a mixercontrol and pilot pointto keep a check on thereproduction.

Circuit DetailsFig. 4 shows the

scheme adopted, anda preliminary study ofthis circuit, in con-junction with the otherillustrations, will moreclearly define the rea-sons governing the lay-out. The mixer circuitmakes provision fortwo microphones, butthere is no reason whythis should not be in-creased to three or

four, providing these are kept to the samecircuit potentiometer sequence.

The microphone jacks MJI and MJ2 arefed through the medium of these potentio-meters to the grid of a Hivac midget

21

x10

0/8

5EE TEXT

,

,,v.;TRANSFORMisg.IXING HOLES>c,

UNt,T,SANG

3Y2'

FIXING HOLES FORRUBBER FEET (CU'

(SEE rEXT)

Fig. 2.-Constructional details of the casing.

pentode of the type X.Y, the " earthy " endof this mixer circuit being directly connectedto the negative line and frame.

It will be apparent, therefore, that asomewhat higher anode current will flowthan would be the case if grid bias wereintroduced, but, as the lesser of two evils,namely that of either increasing the size ofthe unit to accommodate a dry cell, or pro-viding a separate battery, as against a low

T. (since excessive gain is not desiredhich could soon introduce microphone

distortion through overload), the latterconsideration is preferable.

The transformer chosen is from the Bulginrange, and is of the filter feed type; but in

iew of the necessary primary load restric-tion to a safe maximum current of 1 to1.5mA, the screened -grid circuit depictedwas decided upon, and, by so doing, theanode circuit could readily be commissionedfor the pilot phone tapping.

The simple volume control in parallelFIX SO THAT FLANGE ISTOWARDS TOP OF UNIT

WHOLE FORVALVE HOLDER

E 8A

17/8'

Fig 3.-Details if valveholdei bracket.

with the pilot phone jack PJ only effects aslight change in screen current by .ImA atthe maximum H.T. setting of 48 volts, thisvariation falling, of course, proportionallywith any decrease in H.T. This point,however, is important in so far as theresistance of the pilot phones is concerned,and is based on 2,000 -ohm earpieces, withthe potentiometer at maximum.

It must be remembered, therefore, thaton no account should the headphone jackbe removed unless either the pilot volumecontrol is mid -scale to zero setting, orpreferably when the unit is switched off, asa surge of anode and screen current will takeplace; the normal maximum screen currentwith phones in circuit should read .71mAat 48 volts.

For any increase in L.F. gain above thatprovided on 48 volts, a slightly modifiedcircuit will be necessary introducing gridbias, but the operating conditions of thecircuit here will meet the majority ofrequirements admirably, whilst the fact thatexceedingly good results are obtainable evendown to 36 and 24 volts, examples anotheradvantage in the design, namely ease ofportability. A well balanced componentlayout, with rigidity as an importantfeature, combine to make the unit a truefacility and a pleasure to handle.


ConstructionNo. 18 gauge aluminium is employed for

the unit box, a * in. ebonite base beingused, for neatly mounting the transformer.Fig. 2 gives full constructional details forthe unit box and base.

All large drillings for the components,excepting the on -off switch drilling, shouldbe % in. clear, the jack drillings requiring aslightly larger (but less than in.) diameter.All other holes, including those in theebonite, are carried out with is' in. bit, the

M.J.2

four holes for the rubber feet being counter-sunk as depicted, whilst for neatness, it ispreferable that the transformer fixingscrews which are 6B.A, should be of thecountersunk type, let in through the under-side of the base, and secured with nuts onthe transformer. For this reason, then, theholes should be countersunk. on the under-side.

It will be seen in the diagram, that fourother holes are required either side of the

Components for the Amplifier and MixerUnit

PILOT BULB FITMENT1- -type, D19 (red) miniature

signal fitting Bulgin1-type, B206 BulbPOTENTIOMETERS1-100,000 ohms (without

switch) . . Erie2-250,000 ohms (without

switch) _ .VALVEHOLDERS1-type, X114 midget (with

soldering terminals) Clix (B.M.P.)JACKS AND PLUGS3-open circuit type (midget) Igranic3-type, P38. Plugs . BulginSWITCH1-type, S8OT BulginVALVE1-type, X.Y.2 HivacSPADES, PLUGS2-type, MPIa plugs (red.

black) . Clix)2-type, R415 spade ter- }(B.M.P.)

mmals (red, black) . Clix)TRANSFORMER1-type, L.F.12 ... BulginKNOBS2-type, K58 Bulgin1-black wheel type knob .. Webb's RadioDIALS2-type, IP7 . . BulginUNITAluminium box Peto- ScottEbonite baseMISCELLANEOUS6BA nuts and bolts BulginShakeproof washers for 6BA

boltsPush -back wireRubber feet and washers .

Solder tagsH.T. Battery (see text re

L.F. gain and bias adjust-Drydex

L.T. 2v. accumulator ExidePHONESEricsson

Figs. 4 and 5.-(Left)Theoretical circuit dia-gram of the amplifierand mixer unit. (Right)Layout of the com-ponents and wiring dia-

gram.

ows

ammo

OUTPUT TAGS

LT

(2 V.)

LT. -t

VC.3

ACROSS PHONEJACK LOCATED I $BEHIND TRANS-- +LT.-FORM ER

transformer fixing holes, two of these(marked W ") are for passing through theL.T. leads (see the wiring diagram Fig. 4),the other two (marked T ") are for fixingthe output tags. The positions of theseholes are not critical, and can be determinedafter temporarily positioning the trans-former. Make sure they clear the unitflanges when the base is finally fitted.

The above comment also concerns theunit to base fixing screw holes indicated bythe asterisks.

The box construction needs little explana-tion here, but as the fixing -screw holes arenot designated in any way, it would be aswell to mention that these are simply equi-distant, and can be drilled for 4 or 6B.Abolts, as desired.

Wiring and AssemblyWith regard to the wiring and assembly.

after mounting the box components, thetransformer and base fitments should beassembled in readiness for wiring after deal-ing with the rest of the unit. The valveholder, which is mounted on a separatebracket (see Fig. 3), should not be mountedin the unit until the other connections havebeen made.

The potentiometer wiring, and that of thejacks MJ1 and MJ2, should be arranged sothat it will not foul the valve when this isfinally fitted. The valve base wiring can becarried out with suitably determined lengths

M...t I

MJ2

ON/OFF SWITCH

TO SLEEVE CONTACTON PHONE JACK (PJ)

TO 'E' TERMINALOF TRANSFORMER

TIP CONTACTOF PHONE JACK (PJ)

H.T. LEADS PA SSTHROGH GROMMET

4 11 HOLE ,BACK OF UNIT+ HT.- (OPTIONAL)

of wire, since the bracket will still be" floating " for convenience in handling.Similarly, the transformer connections may

_be made, then neatly adjusting all leads, thevalve holder and base can be fitted, twoscrews or small terminals and shakeproofwashers serving to clamp the base.

There is one point concerning the jacks-it will be necessary for these to be turnedwhen fitting, so that the switch and trans-former are not fouled, and in the case ofP.J it will be necessary to use the spacerwashers on the front of the box, andnot behind the jack as is normally thecase.

All wiring which might prove confusing.due to the perspective of the diagram (theview taken in the wiring diagram Fig. 5, isthat which would be apparent if the back ofthe unit were removed) is correspondinglylettered in the circuit Fig. 1.

The X.Y tags are connected (preferablyby screened leads) to the pick-up terminalsof the radio set, a separate earth being madeat the unit if desired, by connecting to L.T.negative.

In conclusion, we -would like to re-commend quite strongly the economicaluse of cone speakers as very able makeshiftmicrophones, the opening comments in thisarticle being fully complied with by thismeans, as proved after extensive experi-ments under normal ' home broadcast "conditions.

New Porn -Porn GunE of the chief dangers to convoys is

\-/ the dive -bomber, and it is now believedthat Britain has found an answer to thismethod of attack. It consists of anti-aircraft guns of a new type, together with aballoon barrage. The balloons keep thebombers high enough to prevent accuratebombing, and if they come low enough toshoot at the balloons they can be fired on bythe new guns. The gun is of the many -barrelled pom-pom type, firing shells of1 in. or more calibre, so delicately madethat they explode on the slightest contact.

Man-made LakeLAKE MEAD, a section of the Boulder

Dam, Colorado, is claimed to be thelargest man-made lake in the world,according to a report submitted to Mr.Harold Ickes, Secretary of the Interior.Its storage capacity is estimated at32,359,274 acre-feet, nearly 2,000,000 morethan the original estimate. The lake isfilled by the winter snowfall, and will solvethe serious drought problem which hasconfronted many farmers in West ernAmerica.


"MOTILUS" PEEPS INTO THE

Pilots bang taught how to recogiise different types of warships by means of wooden models atthe R.A.F. School of Air Navigation.

The Foire de ParisTHE Foire de Paris was held as usual

this year, but scarcely had it closedits doors when the Germans entered

Paris and, therefore, unfortunately, thebusiness that was being transacted as aresult is now in a state of suspense and willbe so for the duration. Messrs. Bassett-Lowke, Ltd., had a small but attractiveexhibit at the office of the Federation ofBritish Industries, which included a gauge" 0 " model of the L.M.S. Royal Scot, aship's motor lifeboat, and a waterline modelof the crack French liner Normandie,together with a selection of boiler, shipsand railway fittings. It is hoped that thispropaganda for export trade will bringbetter results in the future.An Armoured Train

ON page 35 is illustrated a relic of thelast Great War, 1914-1918-a toy

armoured train produced in America bythe Lionel Corporation and is gauge " 0 "electrically propelled. Looking at it in thelight of 20 years' progress, it seems rathera crude affair. To -day scale models areproduced in mass that are really somethinglike their prototypes, but this does not alterthe fact that this armoured train wasliterally " sold in thousands " during thelast war. It was attractively finished inbattleship grey.Miniature Warships

APART from the use of models in con-nection with inventions for winning

the war, miniatures of the fighting fleets ofthe world are utilised in many ways. Pilotsof the R.A.F. and the Fleet Air Arm aretaught to recognise the different types andnationalties of shipping with the aid ofscale waterline models. The fine achieve-ments of the Fleet Air Arm in navalengagements recently, in dive bombing,fire spotting." and in general reconnais-sance had their modest beginning in thestudy by pilots of these actual models ofenemy warships.

(The Fleet Air Arm, originally under thecontrol of the Air Ministry, has, since

May 24th, 1939, been controlled entirely bythe Admiralty and for this reason officersof the F.A.A. wear naval uniform, thoughat present many F.A.A. pilots are R.A.F.

The Use of Mofficers who have been seconded to theNavy, but they are being replaced by navalpersonnel as these become available.)

Model Locomotives

rAAMONG 2i -in. gauge model locomotiveowners and builders, Mr. C. Courtice is

certainly to the forefront as an admirer ofall types of amateur work, and is at thesame time a competent builder who hasintroduced on his models many interesting

gadgets. Illustrated is his 21 -in. gaugeG.E.R. 1,500 class, built from Bassett-Lowke castings by the owner. The featureof this locomotive (and also his L.N.W.E.Jumbo of the same gauge) is that they arecontrolled by an electro-pneumatic systemof his own design. In a horsebox or similarvehicle is housed a permanent magnetelectro-motor coupled to an oscillatingcylinder which creates either a pressure orvacuum according to the direction theelectro-motor is turning. From the oscillat-ing cylinder a pipe is led which terminateson the vehicle in the form of the ordinaryWestinghouse or vacuum brake couplinghose. Electric current is fed to the motorby the usual third rail connected by a shoefitted to the vehicle. According to thepolarity of the current applied to the thirdrail, a vacuum or pressure is created in thehose connection. On the locomotive isfitted a simple cylinder bore by Fin.stroke, the piston of which is connected byrod and bell cranks to the throttle lever,thus operating it in either direction. Thesaid cylinder being of diminutive size, isconcealed under the footplate and thereconnected to a similar hose pipe on thetender buffer beam. It is only necessary tocouple a loco to the "controller" vehicleand connect the " brake hose pipe," whenthe train can be completely controlled inspeed, starting, and stopping by merelyapplying current to the third rail, using

odels in Wartimeany standard controller switch employed inelectrically driven railways. In the Owner'swords, " The main appeal of this system isits extreme simplicity. I have demon-strated its working to a number of people,who agree that, except that the locomotivecannot be reversed on this system, the co -trolling effect is equal to an electricallydriven railway, but with the added attrac-tion that the locomotives were steamdriven."

A 2.12 in. gauge G.E.R. 1,500 class model locomotive built by its owner, Mr. C. Courtice, ofStanford -le -Hope, Essex, from Bassett-Lowke model castings.


MODEL WORLDThe " Heather Glen "

ON this page is shown a picture of theHeather Glen, deemed by her maker

to be the world's fastest model yacht. InJuly, 1939, she won the British champion-ship cup after one week's racing, and thefollowing week she gained the InternationalChampionship cup. But here is her history.Towards the end of the " gay nineties,"there was built in a famous yacht -buildingyard on the Clyde a 23 -metre racing yachtcalled the White Heather. Among the skilledoperatives on this super craft was a youngboat builder who bore the famous surnameAlexander I Being Scottish, he was "canny"and capable and quickly made progresstowards the top rung on the ladder of sailingcraftsmanship. He became first man, thenmanager in sailing yachts, he then superin-

thus obtaining the British trophy. In afurther three days' sailing, the championyachts of Norway, France, Germany, andSweden were met and well beaten byHeather Glen. In those memorable days atFleetwood-July, 1939-she took the leadin the first day's sailing and never lost it,and, to cap the lot, not content with thebeautiful silver trophies-British and Inter-national -,--she carried off the Carpentertrophy (known as the " Wing to Wing "Cup) for the fastest run down win in theInternational series. This run was also arecord for the Fleetwood lake.

For the benefit of beginners in the noblesport of yacht racing, Mr. Alexander says,let your motto be " Try, try, and tryagain." For 10 years the Heathers havebeen competing for the blue riband of

A model exhibited at the Foire de Path-this summer.

tended the construction of flying boats, andsome fifteen years later he founded abusiness for building of miniature racing sail-ing yachts. These boata are now well knownthroughout the British Isles-the WhiteHeather, or shall we say the Alexander' boats.Heather Glen was an A class racing modeldesigned and built by Alexander and sailedby the brothers James (skipper) and Bill(mate) Alexander, she defeated in six days'sailing at Fleetwood 30 British Opponents

model yachting. Twice they have beenrunners-up, once fourth, and once fifth.These White Heather models are, not toys,but are designed very scientifically andconstructed very carefully and should besailed very skilfully. Indeed, since thesemodels have to be sailed without a steers-man, they are probably more carefullydesigned than their larger sister craft. InHeather Glen, for instance, the length on thewater line, and on the quarter beam, the

The "Heather Glen" at Fleetwood.

square root of the sail area, and the cuberoot of the displacement (weight) have to bemost carefully calculated in the design, tomeet the requirements of the rules underwhich these miniature craft compete.

Models to BuildCOLLOWING on the success of the set ofI finished parts for making an L.M.S. 2-6-0Mogul in gauge " 0 " steam-a set whichwas prepared for the model enthusiastowning few workshop tools-Messrs. Bas-sett-Lowke, Ltd., have introduced a steammodel for the advanced model builder.

This is a finch scale, 2i -inch gaugeL.N.E.R. " Flying Scotsman,' of which afull set of castings and finished parts areavailable, together with full-sized workingdrawings. The making of this model is des-cribed and illustrated in a booklet reprintedfrom " Practical Mechanics," edited byMr. F. J. Camm, and this can be obtainedpost free for 8d. or, if purchased at aBassett-Lowke establishment in London orManchester or Northampton, at 6d.

This is the first time that the building of ahigh-pressure scale model has been so com-prehensively handled, and it should find abig response from all keen model locomotivebuilders. The drawings provide for either awatertube or solid fuel boiler.

1?1,111It'd train, !MIMI itt ItIn'ti 1,11 the 1.,1011., (',111,,,111011ofthe last war.


Facts About Metals(Continued from page 540 of September issue)

PPalladium.-Metallic element. Chemical

symbol, Pd ; At. No. 46; AL Wt. 106;M.P. 1549° C. ; B.P. 2820° C. ; Sp. Gray.11.9 ; Sp. Ht. .0582 ; Coef. Exp. .00001176.

Like all the platinum metals, of whichgroup it is a member, palladium is foundin the metallic state alloyed with platinumand its allied metals. Discovered byW. H. Wollaston in 18034, and namedby him after the minor planet Pallas,which had been discovered about thesame time.

Palladium is a greyish -white metalwhich is fairly ductile and malleable. Itis softer than platinum and has a lowermelting point than the latter. Althoughscarcer than platinum, it is commerciallycheaper, because it is not in such greatdemand. Palladium is the only one ofthe platinum metals which will dissolvein a single acid, it being soluble in hotconcentrated nitric acid. Palladiumpossesses the remarkable property ofbeing able to absorb or occlude a largequantity of hydrogen gas, 1 part ofmetallic palladium at red heat being ableto absorb about 900 parts of hydrogen.Several applications have been made ofthis interesting property.

Alloyed with gold, palladium whitensthe metal, several of the " white golds "being gold -palladium alloys.

Palladium also alloys with -lead, tin,nickel, copper, antimony, and bismuth.Salts of palladium have been used inphotography in the production of " palla-diotype ' permanent prints.

Palladium Bearing Metal.-An extremelyhard alloy, sometimes used in watchesinstead of jewelled bearings. Composi-tion : palladium, 24 parts; gold, 72parts ; silver, 44 parts ; copper, 92 parts.

Palladium Leaf.-Very thin palladium foil,which is sometimes used for " silvering "purposes. Palladium leaf can be producedin thicknesses of as little as 1/200,000 ofan inch.

Partinium.-An alloy introduced in Francesome years ago for bicycle and motor-car fittings. It is light and strong.Average composition : aluminium, 88.5%copper, 7.4%; zinc, 1.7%; silicon, 1.1%;iron, 1.3%.

Pearlite.-The " pearly constituent ofsteel." It is a mixture of cementite (aniron carbide) and -pure iron, and, underthe microscope, it has an appearanceresembling mother of pearl. Annealedsteels contain a large proportion ofpearlite.

Pencil Alloy.-A metallic composition whichleaves a heavy mark when drawn acrosspaper and can therefore be used as apencil core. Since it contains mercury,it is an amalgam. Composition : lead,70 parts; bismuth, 90 parts; mercury,8 parts.

Permalloy.-Name given to a class ofnickel -iron alloys originally developed in1921 by the Western Electric Company.of America. The original " Permalloy "contained 78.5% nickel and 21.5% iron,all impurities being kept down to aminimum. After suitable heat -treatment,such alloys develop a remarkable mag-netic permeability, and much use hasbeen made of them in radio and electricalwork on this account. '

LIST OF ABBREVIATIONSThe following abbreviations are used through-

out this Dictionary:Atomic NumberAtomic WeightMelting PointBoiling PointSpecific GravitySpecific HeatCoefficient of Expansion

Therm. Cond. ... ... Thermal conductivityElec. Cond. ... ... Electrical conductivity

Pewter.-Name given to a number of lead -tin alloys which have been put to exten-sive uses since the -Middle Ages. Somepewters contain small amounts of copperand/or antimony. The so-called lead -less pewters " made nowadays are usuallyunalloyed tin.

Pholin's Alloy.-A silver -like alloy contain-ing a trace of mercury. Composition :bismuth, 19.26%; tin, 76.9%; copper,3.84%, plus mercury, a trace.

Phosphor-Bronze.-A copper -tin alloy con-taining a small percentage (about .10) ofphosphorous. It is a hard, fine-grainedyellow -coloured metal having great tough-ness and a high tensile strength.

" Low Tin Bronzes " contain from3.5% to 5% of tin, whilst " High TinBronzes " contain from 4.5% to 7% tin.For special purposes, phosphor -bronzecontaining up to 9% of tin is available.

Phosphor Tin.-This is really a tin phos-phide, containing about 21% of phos-phorous. Although it is silvery -white incolour, it is not metallic. Made by heat-ing tin with phosphorous out of contactwith air.

Pig Iron.-This is a crude form of ironwhich, after smelting from its ore, hasbeen allowed to run off into channelsand moulds and to solidify in the form ofingots or " pigs." of about 3 ft. longand 3-4 in. thick. It is of varied composi-tion, a typical grade of pig iron contain-ing, in addition to iron, about 4% ofcarbon and 2% of silicon together withsmaller amounts of sulphur, manganeseand phosphorous. Some of this carbon iscombined with the iron, some of it ismerely dissolved in the iron. If much ofthe carbon is combined, the metal has alight appearance and is known as WhitePig Iron. If the majority of the carbonis merely dissolved or " free," the metalappears grey and is known as " GreyPig Iron." Intermediate types areknown as " Mottled Pig Iron."

Pig iron is not malleable or ductile. Itcannot be worked or welded. It can onlybe used for the production of castings.Hence its well-known name-" CastIron."

Pig or cast iron forms the startingpoint for the manufacture of wroughtiron and the various steels. It has arelatively low melting point (1,200°C.).

Platinite.-A nickel -iron alloy containingfrom 42% to 50% of nickel. Its co-efficient of expansion is similar to that ofglass, on account of which it is used inthe form of wire for embedding in orpassing through glass, thus providing anabsolutely gas -tight glass -metal joint inelectric lamps, radio valves, etc. Itreplaces the much more costly platinumwhich was formerly used for this purpose.Is often employed in the copper -coatedstate, which provides a still more securebond between glass and metal.

Platinized Asbestos.-Platinum powderdeposited on asbestos, and employed insuch form on account of its chemicalactivity. Prepared by soaking goodquality asbestos fibre in a solution ofplatinum chloride and then stronglyheating it.

Platinum.-Metallic element. Chemicalsymbol, Pt.; At. No. 78; At. Wt. 195,M.P. 1,755°C. ; B.P. 2,650°C. ; Sp. Gray.,21.45; Sp. Ht., .03243; Coef. Exp..00000886.

The best-known and most usefulmember of a famous family of " noble "metals. Occurs always in the metallicstate alloyed with palladium, iridiumand allied metals. Its costliness isoccasioned not only by its naturalscarcity, but, also, by the operations of a" ring ' of producers.

The metal was first recognised as anindividual one by R. Watson in 1750.Previously, it had been known to SouthAmerican Spaniards under the name of" platina," this term being the diminu-tive of the Spanish, plata, meaning" silver." " Platina," therefore, was the"little silver." It was considered as adross in silver, and at one time wasactually thrown away by order of theSpanish Government in order to preventits being used for adulterating gold. Thescientific use of platinum dates fromcomparatively recent times. It is a whitishmetal, with a greyish tinge. It is malleableand ductile and will take a very highpolish. On account of its coefficient ofexpansion being about the same as that ofglass, platinum wires were long used forsealing in the glass of electrical devices.Substitute wires are now used for thispurpose.

Platinum is used in the jewellery,electrical and scientific -instrument tradeson account of its well-known permanentqualities. It is one of the most useful ofmetals. Its salts are used in photo-graphy in the " platinotype " process.Platinum salts are highly poisonous. Plati-num itself alloys with a large number ofmetals.

Platinum Alloy.-A thickly -fluid lead -greyMetallic mass. It is made by grindingspongy platinum with hot mercury.

Platinum Black.-A velvety black powderconsisting of finely -divided metallicplatinum which is highly chemicallyactive, particularly when freshly made.Prepared by adding a reducing agent,such as formalin, to a solution of platinumchloride.

Platinum Black will absorb as much as100 times its volume of oxygen orhydrogen.

Platinum-Bronze.-Name given to a groupof alloys containing from .5% to 10% ofplatinum. They polish well and retaintheir lustre for a long time, whilst theyand relatively inexpensive. A typicalplatinum -bronze composition is : plati-num, 0.9%; nickel, 90%; tin, 9%.

Platinum Metals. --A family of six metals.having similar properties and appearancesto platinum. These are : ruthenium,rhodium, palladium, osmium, iridium,platinum. The first three are sometimestermed the " Light Platinum Metals,"and the latter three the " Heavy Plati-num Metals " on account of their differ-ences in specific gravity.


QUERIESGA1.4

tLr ENQUIRIES

Preparing ChlorophyllCAN chlorophyll be extracted from leaves

by heating them with methylatedspirit ? Is it possible to prepare pure chloro-phyll ?-S. C. (Glamorgan).T is not a difficult matter to prepare aI

pure chlorophyll extract. Simply warmchopped fresh green leaves with methylatedspirits (or, preferably, rectified spirits) forseveral hours. Then filter the green solu-tion and evaporate it. The pure plantchlorophyll will then be obtained as agreen amorphous or non -crystalline mass.Its composition is unknown. but it isnoteworthy that it contains magnesium.

Testing for SugariS there a simple test by which the presenceI of sugar, or other carbo-hydrates (includingformaldehyde) may be shown in eitherchlorophyll or an alcoholic solution ofchlorophyll ? If so, what is it ?--A. B.Wilts.).CHLOROPHYLL is a definite chemical

compound and, as such, does notcontain any sugar or formaldehyde.

Furthermore, there are many differenttypes of sugars, so that we should have toknow with which one the chlorophyllextract was contaminated before we couldadvise you fully on the detection of sugar inchlorophyll mixtures. Assuming, how-ever, that the sugar in question wasFructose or Levulose, fairly small amountsof it could be detected by boiling the extracttt ith an equal bulk of Fehling's Solution,whereby the sugar. if present, would reducethe blue Fehling's solution to red copperoxide.

The " Electron'. MicroscopeWHAT is the principle of the "Electron

Microscope" ? Can you tell me thename of a book which explains the instru-ment and what is its highest magnification ?

-A. S. (Bristol).THE precise mode of operation of the

Zworykin " Electron Microscope " hasnot yet been fully disclosed. The Zworykininstrument, however, uses electrons insteadof light rays for magnifying purposes and themagnified objects are projected on to afluorescent screen. In principle, the elec-t rons emitted by the object under micro-scopical examination are focused by apowerful magnetic field and the focusedimage, much magnified, is shown on thefluorescent screen after the manner of atelevision image.

The highest magnification obtained byt he Electron Microscope is of the order of1,000,000 times, but it is reported thatthe instrument is capable of even greatermagnifications.

There is no published book on thi.ject so far.

Making Carbon MonoxideHOW is carbon monoxide prepared? Is

the preparation of this gas dangerousIf carried out in the open air ? What

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 reader. Send yourqueries to the Editor. PRACTICAL MECHANICS.Geo. Newnes, Ltd., Tower House. Southampton

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

chemical could be used to absorb this gasor render it harmless ?-A. D. (Manchester).

CARBON monoxide, CO, is best pre-pared by heating formic acid or a

strong solution of sodium formate withconcentrated sulphuric acid. In practice,the strong sulphuric acid should be con-tained in a flask provided with a deliverytube and heated to 11)0' C. The strongformic acid should then be dropped into thesulphuric acid, and as each drop of theformic acid enters the sulphuric acid, purecarbon monoxide will he given off.

Carbon monoxide is an excessively powerfIdpoison and, even when prepared in the openair, the experiment is not without danger.If, therefore, the preparation of this gas iscarried out, the experimenter shouldkeep well away from the table or bench.

Carbon monoxide is absorbed by asaturated solution of cuprous 'chloride inconcentrated hydrochloric acid or ofcuprous chloride in ammonia. Thesesolutions do not decompose the gas; theymerely dissolve it. Some, however, suggestthat the carbon monoxide combines withthe cuprous chloride, forming the compound--2Cua.00.211,!0. Carbon monoxide isnot appreciably soluble in water, and thuscan be collected over that liquid.

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purchasing new ones from their Ironmonger.Sold by all good Ironmongers and Stores. Catalogue from

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Good Englishis the one assetthat you musthave if youare to makeanything ofyour life.

Learn by post to express yourself clearly andforcefully and to avoid embarrassing errors. Writeto -day for free booklet.THE REGENT INSTITUTE (Dept. 321E),

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Terms: Cash with Order."CRYPTO" D.C. TO A.C. CONVERTOR, 220 D.C. to200 volts A.C. 50 -cycle 1 Phase 500 Watts, in perfectcondition, £5 10s.. carriage forward."CROMPTON" SELF -EXCITING ALTERNATOR.50/70volts 50/100 cycles, in good condition. £3 Ms.. car-riage forward.D.C. BLOWERS, 2 In. inlet and outlet, Aluminium bodyLaminated fields, ideal for dugout ventilation, will workquite well from 150 volts, a.c. 20 - each, carriage 1/6.MAINS TRANSFORMERS, 200,240 volts, 50 cy. 1 ph:output, 12 x 24 volts. 4/6 amps., 15,'- each. post 1/-.Ditto, 100 volts, 40 m/a and 4 volts, 1 amp., 3/- each,post 9d. Ditto 5 and 7,000 volts, at 10120 m/anms.. 6/6each, post 1/-. Ditto. 50 volts, 618 amps., 151- each,post 1/6.MAGNAVOX P.M. PUBLIC ADDRESS HORNSPEAKERS, handle 15 20 watts. Size of horn 40 in. by20 in. flare, 47/6, carriage paid.DOUGLAS PORTABLE LIGHTING ENGINE, 2l h.p.Twin Special Air Cooling, complete with all fittings.including petrol tanks, etc.. fully protected. Conditionas new, es 15s., carriage forward.DYNAMOS, for charging or lighting, etc. All shuntwound and fully guaranteed, 12/18 volts, 8/10 amps..2,200 r.p.m., 37'6. 30 -volt, 10 amp.. 1,750 r.p.m., 601-;100 volt, 10 amp., 4 pole, 1,500 r.p.m.. 90/-. Wig volt.15 amp.. 1,750 r.p.m.,95'-. 200 volt, 12 amp., 4 pole, 1,750r.p.m.. £510s. 25 volt, 8 amp., 1,750 r.p.m.,3216. All carriageforward.EX-G.P.O. SMALL RELAYS, 2,000 ohms with multicontacts, 5 each. Ditto, 2,000 x 3 ohms, 5/-. Ditto, 7.000ohms, two leave type, 3/6 each. Useful for remotecontrol, etc.VOLTAGE CHANGER TRANSFORMERS (AutoWound). 110 to 250.240 volt or vice versa. Guaranteed12 months. 250 watts. 25:-; 500 watts. 32;6: 1,000 watts51L-; 1,500 watts, 2 k. watts 75:-. Delivery 7 days fromdate of order.REGULATORS. STARTERS AND LARGE DIM-MER RESISTANCES. Stud Switcharm type. Pleasestate requirements.SWITCHBOARDVOLTAND AMPMETERSMOVINGCOIL AND MOVING IRON. All first class makers.Please state requirements.ELECTRIC LIGHT CHECK METERS for D.C. Mains200/250 volts, 5 and 10 amps, in new condition, 4.6 each1/- post.NEWTON" MOTOR GENERATOR, 221) volts D.C..

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"Go to ItIf you want to get right down to aspeedy and sure way of becoming ahighly efficient Morse operator, get it

the Candler wayThe Candler system of Code Training wasdevised for those who intend to enter orhave entered the commercial side of tele-graphy, the Services, or who take a realinterest in Amateur Radio work.

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1040


Highest MagnificationWHAT is the highest magnification

possible with a modern opticalmicroscope (both monocular and binocular) ?--E. R. (Reading).

THE highest practical , magnificationobtained by means of an ordinary high-

class commercial microscope is about1,500 times. With a binocular microscope,the highest practicable degree of magnifica-tion is very much less than this, seldomexceeding 400 times.

A Leaky RadiatorWHAT is the compound used to sealV. V radiator leaks ? I believe it containsleather filings. Is this correct ? -W. F.(Clapham, S.W.4).

A. MIXTURE of lithage (lead oxide) andasbestos powder, or of red lead and

putty will seal radiator leaks in a temporarymanner, and provided that the sealed partsare not strained in any way, they may, insome instances, last for a considerable time.

Sometimes solutions of iron chloride andcarbonate of soda are added to the radiatorwater, whereby brown iron carbonate isprecipitated in the water and, beinginsoluble, tends to seal up a tiny radiatorleak. All such methods, however, are, atthe best, purely temporary ones.

Liquid CementCAN you give me the recipe for making

liquid cement and a wax car -bodypolish ?-C. V. (Watford).LIQUID jointings vary enormously in

composition. A good one consists of athick solution of orange shellac in methy-lated spirits which is mixed to a thin pastewith red or white lead. Others consistof thick shellac solution and goldsize mixedin about equal proportions.

In order to make a wax car -body polish,melt an ounce of beeswax or earnauba wax(or a mixture of both) in about double itsweight of turpentine. This, when cold,will set to a solid, pastey mass.

A liquid polish of the same nature canbe made by diluting the above with fouror five times its volume of white spirit.

Another liquid polish consists of a solu-tion of ammonia in spirit, but this isexpensive and unsafe to use.

Running -In CompoundCAN I make a running -in compound by

blending graphite with mineral oils ?-W. H. (Woking).

YOUcannot possibly blend graphite

with mineral oils in order to produce arunning -in compound, for such blendingrequires the use of a " colloid mill," anextremely expensive apparatus in whichthe graphite is actually ground into the oil.Even the finest graphite which you couldbuy would not produce a running -in com-pound by an ordinary simple stirring intothe oils.

RaysI S there a method of detecting the presence

of infra -red and ultra -violet rays ?--S. T. (Plymouth).

FORthe detection of infra -red rays, your

best plan is to use a camera and an infra-red colour -filter together with an infra -redsensitive plate or film. Such materials maybe obtained from Ilford, Ltd., Ilford.

With the infra -red colour -filter in positionover the lens, the pieces of glass are photo-graphed against a background illumined by

the rays of an electric lamp, an infra -redsensitive plate or film being Used for thepurpose. If the glass passes infra -red rays,it will appear more or less transparent inthe photograph, whilst if it does not passinfra -red rays, the glass will appear darkgrey or black in the photograph.

Other methods of testing the presence ofinfra -red rays depend upon the use ofextremely delicate thermocouples or elsean instrument known as a " bolometer,"hut all such methods are far too expensiveand delicate for an amateur to apply.

In order to test for the presence of ultra-violet rays, use a solution of quininesulphate in diluted sulphuric acid. This,in the presence of ultra -violet rays, has astrong, bluish fluorescence.

Frosting- A WindowCAN you tell me the simplest method of

frosting a window ?--N. 0. (Middles-brough).

ONE of the best and simplest methodsof frosting a window consists in giving

it a thin coat of clear celluloid solutioncontaining in it a small proportion of chalkor talcum powder.

Mix together one part of acetone and.1 part of amyl (or butyl) acetate, whichliquids can be obtained from your localchemist and in these mixed liquidsdissolve, with vigorous shaking, clearcelluloid until a varnish the consistency ofpaint is obtained. Into this varnish stir asmall proportion of talcum powder orsome other similar material so as to give thevarnish a slightly opaque appearance.

Now paint this varnish on to yourwindow, using a flat brush for the purpose.Give your window about three hours to dry,and afterwards, you will find that you haveobtained an excellent frosted effect.

Oxidising EffectCAN you tell me how sheet steel, which is

blue when purchased, and tinplate canbe given an oxidised effect ? The appearanceI desire is similar to that seen on fire -screens,coal boxes, etc.-R. C. (Sussex).SHEET steel and tinplate can only

satisfactorily be given the oxidisedfinish you desire by :

(a) Varnishing over with a brown lacquer,Or

(b) Copper plating and then by immers-ing the copper -plated article in a very weaksolution of sodium or ammonium sulphide.

The articles to which you refer (fire -screens, etc.) are usually surface -colouredby simple lacquering. We think, therefore,that this will be your best plan to adopt.Go to your nearest paint store and procurea quick -drying lacquer of the shade youdesire. This may usually be thinned downwith white spirit. It is frequently advan-tageous to apply it to the metal not with abrush but with a fairly large turf of cotton -wool, thus avoiding a hard outline to theacquered area.

WATCHES : ADJUSTMENTAND REPAIR.By F. J. Camm

n up-to-date book dealing with watchmakers'tools, materials and methods of repair. Chaptersare included on the principles of the compensat-ing balance, lever escapement, the cylinder, hair -springing, cleaning, fitting new main springs,glasses, winding stems, pivoting, watch case re-pairs, with useful tables etc. From all book-sellers 6s. net, by post 6s. O., from the publisher:George Newnes, Ltd. (Hook Dept.), TowerHouse, Southampton Street, Strand, W .C.2.

THE USEFULNESSOF PELMANISM

pELMANISMis useful in all the affairs of

life. That is its outstanding recom-mendation to those who wish to make thebest of themselves in their occupations, inall their recreations, and in their socialand cultural relations.

Every line written in the Pelman Courseis directly applicable to some aspect ofhuman life and conduct. The intention ofevery word in the Course is to make clear tomen and women the means by which theycan develop their powers to the fullestextent so that they can live more happilyand be more successful-so that, on the onehand, they will make and use occasions forprofit and advantage and, on the other hand,be at ease in any company. Both conditionsare. necessary to complete self-respect anda full life.

Pelmanists are not left to make theapplications ' 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, "1 feel that this Course wasprepared, for me, and me only." Sub-stantially this is so, for the instructionanotes and letters of advice are entirelypersonal to the individual; they are forhim or her only.

H.M. FORCESAll serving members are now entitled toreceive the complete Pelman Course,with full tuition and guidance, at

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Approved by War Office

The present dominant aim for every manand woman must be to show a courageous,confident, well-equipped mental front. Thisassured, then all else will be achieved, andthe world has no more proven method thanPelmanism to attain this end. Many ofthe greatest Leaders in varying spherestestify this. You may read what they sayin the Free Book offered.

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The Pelman Course is fully explained in"The Science of Success." The Courseis simple and interesting and takes up verylittle time. You can enrol on the mostconvenient terms. The books will be sentyou, gratis and post free, on applicationto -day to

Pelman Institute,(Established over 11) years)

130 Pelman House, Bloomsbury St., LondonW.C. IReaders who can call at the Institute will be

welcomed. The Director of InstructiOn will bepleased to have a talk with them, and no fee will becharged for this advice.

PEL.11.4 N (OVERSEAS) INSTITUTES : NEWPORK : 271 North Avenue, New Rochelle. MEL-BOURNE: 306 Flinders Lane. JOH A NNESBURG: P.O.Hot -1-028. DURBAN : Natal Bank Chambers (P.O. Box

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THROUGHOUT THE LAST WAR OUR MODELS GAVECONSTANT PLEASURE AND INSTRUCTION TO BOYS & MENWe do not know-hostilities may have ceasedwhen you read this announcement-but you maybe sure that-war or no war-we shall use everyendeavour to produce models and sets of modelparts that are of use and help in these days of stress.There must be hundreds of model railway enthus-iasts who aspire to build a "live steam" locomotive,but who have not yet achieved this aim.

NOW IS YOUR CHANCESend for the booklet which interests you. "Buildinga Bassett-Lowke Gauge '0'2-6-0 steam Mogulin 30 hours " or "The Construction of a 21 in.

gauge 4-6-2 Flying Scot." 8d. each, post free -There are still SOME BARGAINS left of modelengineering and boiler fittings. Send for freeSales List No. 12. post free.For the gauge "0" owner are sets of wagons, inG.W.R. or L.N.E.R. colours at less than pre-warprices. 8s. 6d. the set of three. Postage 6d.GR. 12. Gauge "0" list. 3d. TT.I 2. Gauge "00"List. 2d.The long promised new edition of the "MODELRAILWAY HANDBOOK"-completely revised,with new illustrations-over 150 pages. On salethis month. Price 3s. 6d.

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AVAILABLE FORIMMEDIATE DELIVERY

CAPSTAN ATTACHMENTfor 3i" GRAYSON LATHE 15 GNs.Can be supplied to fit almost any lathe at

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Why not get the very best outof your Short-wave listening?

Short waves on the loudspeakerare all very well, but, somehow orother, it seems that the mostinteresting and most sought -fortransmissions are the most distant-and the faintest.This is where ERICSSON SUPER-SENSITIVE TELEPHONES come tothe, aid of the short-wave "fan".They annihilate distance . . .

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The WHY? WHAT? WHEN?and HOW ? of Aviation

THE FLYINGREFERENCE BOOK

By F. J. CAMM

CONTENTS include : Aircraft Specifications. MilitaryAircraft of the World. British Aircraft and Aero EnginesManufacturers. World Aircraft Records. Aerodromesand Airports. Aircraft Number Plates. First FlightsAcross the English Channel. International AircraftMarkings. The Royal Aeronautical Society. The RoyalAero Club. The Society of British Aircraft Constructors,Ltd. The British Gliding Association. The Air Leagueof the British Empire. The Society of Model AeronauticalEngineers. National Association. Careers in Aviation.The Rule of the Air. Airships and Balloons. Winners ofRaces and Trophies. Royal Aeronautical Society Awards.Light Aeroplane Clubs. British Gliding Clubs. ModelAero Clubs. Air Companies. Air Routes of the World.Air Route Maps. The World's Largest Aircraft. NorthAtlantic Flights. England to Australia Flights. GroundMarkings on Aerodromes. Gliding Records. V.C. 's of theAir. British Model Aircraft Records. Important Dates inAviation History. A Dictionary of Aircraft Terms. Index.This work is invaluable to everyone in the Aeronautical

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October, 1940 THE CYCLIST c-35

,--:-. - - ct

CAS_ ,I

Editor : F. J. CAMM

VOL. IXIX OCTOBER, 1940 No. 224

Comments of the MonthBy F. J. C.

Sport and AccidentsTHE minor accident to Kitching in the

North Road " 12," which robbed him ofalmost certain victory when, at 226*miles and 42 minutes to go, he was incollision with an Army lorry, has drawnattention to the immunity from accidentswhich cycling sport has enjoyed for the past60 years. There have been very few fatalaccidents, and that in which Kitching wasinvolved was fortunately not serious.Cycling sport is, indeed, extremely wellorganised. Marshals are arranged at all ofthe danger points on the course. Thecourses themselves are measured, inspectedand approved, and it is only on few occa-sions that an accident occurs. A few havebeen caused by the carelessness of ridersin keeping beads down. There are penaltiesfor riders who bring the sport into disreputein this way.

The accident does, however, confirm thewisdom of those clubs who, in cancellingfamous fixtures, did so in the belief that thepresence of Army lorries, identity -cardinspections, and other military causes ofdelay, might give rise to the very incidentwhich happened in the North Road "

As usual, this " 12 " was well organised.

Immobilising Bicycles

THERE seems to be some confusion ofthought on the part of the police regard-

ing bicycles left unattended by the road-side. The present regulations apply only tomotor -cars and mechanically -propelledvehicles. A cyclist is not compelled todeflate his tyres, to remove the pedals, tochain the wheel, nor in any way to takeprecautions against it being stolen. Inspite of this, some cyclists who have lefttheir machines by the roadside have foundthat the tyres have been deflated and thevalves removed by the police, who haveleft a notice to say that such can bereclaimed by calling at the police station.The cyclists concerned would have beenquite justified in insisting that the policereplaced the valves and inflated the tyres.

It is, of course, a wise precaution to leavethe bicycle in such a condition that it cannotbe stolen; and, indeed, if cyclists could bepersuaded to take these precautions inpeace, as well as in war, the police would nothave on their hands thousands of stolenbicycles which they have recovered, theowners of which cannot be traced. Norwould some tens of thousands of cyclistseach year be deprived of their machines bycycle thieves.

We were told that on the Continent theCerman parachute troops carried, strappedto their backs, folding bicycles, and if the

lermans contemplate a parachute invasion-of this country, it is fair to presume thatthey would not rely upon the stealing of

bicycles or motor -ears to eomplete theirplans.

We were considerably amused to hear,during a talk on bicycles -radiated by theB.B.C., the statement that a bicycle wasone of the most difficult things to immobi-lise. We were also somewhat surprised thatcycling journalists did not take the oppor-tunity to correct the talker, especially inthese days when they have so little to writeabout, It would be thought that such a, pegwould have provided material for consider-able copy and criticism. May we, therefore,correct the. talker by informing him thatthere is no vehicle more easily immobilisedthan a bicycle. The removal of the valves,the removal of the pedals, the loosening ofthe wheel nuts, the removal of the tools, theslackening of the handlebars, the use of alock and chain, the removal of the saddle-these are but a few of the methods ofrendering a bicycle immobile. We presumethat someone vets these broadcast talks.and it is hoped that in future they will onlypermit them when the speaker has .1.11111. -

thing to say.

The Death of Desgranges

THAT hardy old veteran of cycle sport,Monsieur Henri Desgranges, founder of

the Tour de France, and the famous Frenchsporting newspaper LAW°, has died at theage of seventy-six. He set up the first one -hour record in 1893, and for more than fiftyyears had been interested in the promotionof professional sport. The success whichattended his efforts is obvious from the factthat the Tour was front-page news eachyear. There is no cycle event in this countrywhich is considered of sufficient importanceby newspaper editors to occupy front page.In this country our newspapers like toconcentrate on the negative aspect. If fivecyclists are mangled by a lorry, that wouldbe front-page news. If five cyclists escapedfrom being mangled by a lorry, that wouldnot be news at all-an inversion of North-cliffe's doctrine that dog bites man is notnews, but man bites dog is.

The organisation of the Tour remains inthe hands of those whom Desgranges trained,and we have no doubt that the post-warperiod will see a revival of it, as a tribute tothe memory of its founder. Another famouscycling character who died recently wasEdouarcl Michelin, manufactmer of thefamous French tyres bearing his name, liehad a considerable amount to do with thedevelopment of the pneumatic tyre, and atone time was a racing motorist. He died atthe age of 84.

The Social Season Begins

THEsporting calendar is practically at

an end, and the social season of dinners

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

Strand, London, 4r.C.2.

Thom:: Temple Bar 435:1.

Telegrams: Nenne., Rand, London,

and lunches, prize-givings, and dancesbegins. Most clubs intend -to run theiranimal dinner as usual, but many have sub-stituted a lunch because of the difficultiesimposed by the black -out, and becausemany restaurants are refusing to providebanqueting arrangements. The dinners,and the lunches, because of.rationing, maynot be so sumptuous as in previous years.Nearly all clubs have given prize -winnersthe opportunity of selecting and receivingtheir prizes soon after the event, and sothere is bound to be a smaller number ofprize-givings this year. in our view, this isall to the good. There are few things soboring as prize-givings, which are of interestonly to the few. The attendances mustnecessarily be smaller, but the importantthing is to keep the enthusiasm alive.

A number of clubs which formerly used,the London restaurants for their annualdinner have fixed the venue this year out-side London. Others have made it a Sunday(late to fit in with the times of those workingon munitions. Let us hope that whenthe next social season arrives we shallbe -able to drink to the victory of thiscountry.

We shall be glad if clubs will send usdetails of their social fixtures earlier thanusual, in view of the fact that we aretemporarily appearing monthly. By sendingus the details well in advance we shall thusle able to accord them due mild

Steel Studs

THE C.T.C. makes a suggestion that thedangerous steel studs used to markpedestrian crossings should be pulled up

and used to swell the metal scrap -heapwhich help to make munitions. We approvethe suggestion. There is no need for steelstuds and white lines, and as the white linesfollowed the steel studs it is obvious that thelatter failed in the object for which theywere introduced. They are dangerous.They have caused numerous accidents andprevented none; 'they fail to indicatb thecrossing, especially at night. We hope,therefore, that the authorities will removethe studs together with the Belishamemorials adjacent to them. Let us, infact, remove every trace of evidence thatwe once had so incapable a Minister ofTransport as Hore-Belisha, the man whosefantastic ideas on the cause of accidents andtheir prevention resulted in road chaos andthe handing out of unwarranted privilegesto pedestrians.

Air RaidsIN spite of air raids, road sport' goes on.I Some events, indeed, have been runduring an air raid. Now that air raids,however, have become of longer duration,and extend from the evening until the fol-lowing morning, it may be more difficult toearly on. Nothing must be done which willcause the authorities to ban sport. Clubswill, therefore, be circumspect in theirdecisions concerning the running of anevent if the all -clear has not been givenwhen the race is due to start.

THE CYCLIST October, 1940c 36

Photography on ShowTHE annual Photographic Exhibition of the Notts. D.A. C.T.C. is to be held on October19th at the Scout Hall, Shakespeare Street,Nottingham. It will be in four sections : (1)Club -life, contact prints only; (2) Landscape,contact prints only; (3) Landscape, en-largements, and (4) Miscellaneous section. The latestdate for accepting entries is October 1st, and formsare obtainable from D. H. Burton, 12, Hood Street,Sherwood, Nottingham.

Bicycle PoloARRANGEMENTS have been made for the playing

of bicycle polo at Duppas Hill, Old Toms, Croydon(the turning opposite the " old " Waddon Station),every Sunday afternoon starting at 1.30 p.m. Thecharge will be ls. 6d. per player per match, this feemust be paid before the game. Players who haveadditional polo shirts are asked to bring them alongto loan to players who may be selected to play withthem so that the teams can be kept in uniform colours,making it easy for players and referees alike to followthe game. Complete sets of shirts will be available onhire at au additional charge of 3d. per player.

Officials Re-electedTHE previous officials were re-elected at the sixth

annual general meeting of the Western R.R.A.People wishing to get into touch with the Associationshould write to Mr. G. A. Widmann. " Abona," RomanWay, Stoke Bishop, Bristol, 9.

Mrs. Brierclige FailsMRS. BRIERCLIFFE who recently made an

attempt to regain the British women's 50 milesrecord, was forced to retire, owing to cramp, aftercovering nearly two-thirds of the course.

A. R. P. MessengersNOTTING HAM still requires cyclist volun-

teers for A.R.P. work. They will beneeded for messengers and must be over 16years of age. Interested cyclists should makeenquiries at the A.R.P. Headquarters, Gold-smith Street, Nottingham, or from Mr. H.F. Widdowson, 223. Radford Road, Notting-ham.

Cycling InventionsINVENTORS appear to have been very

busy of late in their efforts to improve thebicycle. Patents have recently been takenout for a cycle support, a pedal and crank -driving mechanism, change -speed hub gears,saddle supports and frames and electriclamps.

Miss Wilson has Them AllM155 1i; Wilson, Claud Butler and Sturmey-

Archer professional cyclist, now holdsevery one of the sixteen records on the books ofthe Women's Road Record Associations.Her last was collected on August 20th,when she beat the Glasgow -Edinburgh andback record with a new fastest -ever timeof 4 hrs. 33 rains. for the 88I

Miss Wilson started frOm Gyle Bridge,Edinburgh. at 5.30 a.m. and reached Glasgow

anagramsat 8.16, four minutes slower than schedule. On thereturn, she made full use of the fast finishing miles andreached Gyle Bridge at 10.3 a.m. Despite unfavourableconditions, Miss Wilson finished undistressed.

Previous fastest over the route was put up last yearby Mrs. Ann Briereliffe, West of Scotland Clarion,4-47-14, the Scottish record, although the Britishrecord was 5-3-12, also put up last year, by Miss T. M.Biggs, of London. Fastest man over the route isJ. Dickson, Edinburgh Road Club, with 4-1-17.

Miss Wilson was timed by Mr. a E. Herd, ofEdinburgh, and Charlie Davey, of Sturtney-ArcherGears, was also indhe following car.

Road Sport Support in ScotlandAFTER some weeks of poor support. road sport in

Ayrshire was revived during August. Perhaps themost sensational news from this quarter was thebreaking of the Scottish and English competition 30record by J. McKay, Douglas Water Clarion, in anAyrshire Clarion event.

This miner -cyclist clocked I hr. 12 mine. 45 secs.for the distance, an improvement of 1 mitt. 14 sec.on the previous Scots record, set up last year by WillScott, Crawick Wheeler., and of 16 secs. on G. Fleming'sEnglish record.

Scott also broke his own 30 record in the trial with atime of 1-13-7, and his club. Crawick Wheelers, set upa new Scottish 30 record with 3-44-38. Other membersof the team were Scott's brother, eighteen -year -oldDavid Scott, and J. Tudhope.

The new times are subject to the confirmation of theScottish Amateur Cycling Association.

The Black Watch are now equipped wills bicycles

NOTES OF AHIGHWAYMAN

By L. ELLIS

A Western ParadiseGLOUCESTERSHIRE is pre-eminently a touring

county. It can lay claim to the possession of atleast three recognised touring areas-a large part ofthe Northern Cotswolds, practically the whole of theSouthern Cotswolds and the Forest of Dean. It mightrightly claim a large share of the Wye Valley. Indeed,the river Wye acts as its western boundary for manymiles and tile road that follows the wild convolutionsof this lovely river is largely in Gloucestershire. Inspite of all these touring areas de -luxe some of themost interesting towns cannot be classed under anyof the headings. There are few more interesting townsin the whole of the British Isles than Tewkesbury, nomatter from what angle one regards the subject. Onthe score of history it easily holds its own. Forpicturesqueness it compares favourably with any. Foraccessibility it cannot be excelled. So far as historygoes Tewkesbury can show that it was occupied by theRomans in A.D. 44. It has figured in many famouswars and more than one decisive battle has been foughthi the vicinity. Here it was that Edmund and Canutesettled their argument. In 1471 one of the majorbattles of the Wars of the Itoses was fought at Tewkes-bury-, when Prince Edward was killed. During the CivilWar the town suffered great hardships when it con-stantly changed hands, first to the Cavaliers, then tothe Roundheads.

The Glory of TewkesburyTHE glorious abbey, some say only excelled by

West/ilia-4er in size and dignity, was originallyfounded in A.D. 715. The present building was begun

Painswick Church and a few of the Yew trees.

after the Norman Conquest and some part u -as rebuiltafter a disastrous fire in 1178. It is often said that thegreat central tower is the finest Norman tower inexistence, a statement that one finds easy to believe.Another notable feature is the west front, consistingpractically of one immense Norman arch. In the matterof old houses Tewkesbury is particularly fortunate andboth sides of the long, wide street are adorned withexcellent examples of ancient domestic architecture.More than one famous author is linked with the town.The old Bell Hotel at the Abbey end of the town bearsan inscription reading: " This house is mentioned inJohn Halifax, Gentleman,' as being the residence of

Abel Fletcher, the Tanner." The bowling green at therear also figures in Mrs. Craik's novel. The Royal HopPole Hotel is mentioned in Dickens's " PickwickPapers " as the place where Mr. Pickwick and Mr. BenAllen were so influenced by the quality of the liquordispensed that they slept for thirty miles. One of themost beautiful old houses is the " House of the GoldenKey," a lovely black and white structure, four storeyshigh and crowned with twin overhanging gables. Thisbrief catalogue merely touches the fringe of the host ofdelightful old ',lac -es waiting to be seen, and othersinclude Warwick House, Ye Olde Hatte Shoppe,Clarence House, several old inns and an old mill. Atthe other end of the town from the Abbey is King John'sBridge, overlooked by the Olde Black Beare Inn,bearing the date 1308. Quite close to this spot theWarwick -hire Avon merges with the Severn, near abridge erected by Telford in 1826.

A South Cotswold LegendFARTHER to the south-east of Gloucestershire lie

the Southern Cotswolds, a tract of lovely country butdiffering widely in character from the North Cotswolds.Here the places tend rather to be towns than sleepylittle villages, and there is a greater tendency towardsindustrialism. The district, however, is well worthexploring and the town of Painswick should not beoverlooked. Its aged church is surrounded by a remark-able collection of tombs. Of even greater interest is theruagnifielent collection of clipped yew trees. It is saidthat there are ninety-nine and that all efforts to growthe hundredth have failed. For many years the yewshave been trimmed on September 8th and the follow-ing Sunday is known locally as Clipping Sunday. Onthat day the parishioners march round the churchyardand then form a ring holding hands.

October, 1940 THE CYCLIST

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THE CYCLIST

AROUND THE WHEELWORLDBy Icarus

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The iamb,Barka

Another Pneumatic Tyre

WAS interested to read of an inventionI to provide cyclists with what virtuallyamounts to a spare wheel. Whether theinvention will ever be marketed I am unableto say, but it has been provisionally pro-tected. It is a tyre and the inner tube hasanother tube within it. This second tube ismade of thinner rubber and of slightlysmaller diameter than the main tube. Thus,it lies snugly to the rim when the maintube is inflated, and is itself uninflated.When a puncture occurs in the main tubethe flint or nail causing the puncture isremoved from the cover, and the inner tubepumped up, leaving the cyclist to repair themain tube when he reaches home. I under-stand that the tube is on the heavy sideand thus it would be of little use for acingpurposes.

There have been numerous devices forpuncture -proof tyres, but I am yet to learnthat one of them has really caught on. Inthe first place, punctures are far less fre-quent than they used to be, due to thebetter road surfaces, and in the second, fewcyclists find difficulty in quickly repairing apuncture. The inventor of this new tyrestates that he has been testing one of themfor over six months, and is encouraged tobelieve that the device is entirely satisfac-tory. As the secondary tube lies flat to therim, it is thus protected by the rim when themain tube becomes punctured, and unlessthe nail is unusually long, it is unlikely topierce it.

Another Medal for Monty Southall

FRANK SOUTHALL'S brother Monty hasbeen honoured by the award of the Medal

of the Order of the British Empire forservices overseas. It will be rememberedthat Monty was wounded whilst serving inFrance. He was a Norwood Paragon"crack," and as such accumulated a largenumber of medals among which his presenta ward will take pride of place.

Road Casualties in London1-HE MINISTER OF TRANSPORT has

I recently published the statement re-ceived from the Commissioner of Police forthe Metropolis on road accidents in thefirst half of the present year. From this itappears that road casualties totalled 15,623which compares with 26,630 in the corre-

eponding part of last year. This shows adrop of more than 40 per -cent. Cases ofserious injury numbered 1,327 against2,464 last year, a drop of 46 per -cent. Theslightly injured totalled 13,922 against23,707, a decrease of 41 per -cent. Thedecrease in road deaths has not been somarked, for they totalled 374 against 459,a drop of only 18.5 per -cent. We mustremember that private motoring, both as tonumber of vehicles on the road, and thenumber of miles covered by those whichremain, have dwindled to infinitesimal pro-portions compared with pre-war. Thefigures, therefore, are not so comforting asone might have expected, especially whenwe remember the long period of ice snowand fog, when road traffic was practically ata standstill. According to this statement,casualties at night amongst all road userstotalled 174 killed, and 4,328 injured. Forhours of daylight the figures were 200 killedand 10,921 injured. Included in the 374fatalities were 260 pedestrians. Only 78of these pedestrian fatalities occurred in thesecond quarter of the year, and of the 182deaths recorded in the first quarter, 132occurred during the hours of darkness, anincrease of 46.7 per -cent. over the corre-sponding figure for 1939. Over the sixmonths there was an increase of 21.4 per-cent. in pedestrian fatalities during thehours of darkness.

Letters to the Press

THERE is a peculiar section of the publicknown as writers -of -letters -to -the -press.

They love to see their names at the foot ofa letter, and they keep up a battery ofcorrespondence with editors, giving solutionsto all sorts of national and internationalproblems. I do not suppose that there isone sensible letter in a hundred, and itis difficult to understand why newspapereditors do not exert editorial discretion andhurl the letters into the wastepaper basket.Some of these letter writers duplicate a par-ticular letter, and shoot it off to hundreds ofnewspapers so that the same letter appearsin several newspapers simultaneously. Theyadopt, in some cases, the familiar noms desguerre, such as 'Paterfamilias," "Pro bonopublico," "Father of seven," or "OldSoldier:" 1 am certain that these peoplelive in smug little jerry-built cottagesrejoicing in the name of "Chez Nous,""Dunromin," or "Ourome."

I suppose we must class these people with

October, 1940

those who are fond of using a double-bar-relled name, or smoking a long pipe, and inthis latter class we must, of course, putauthors at the top of the list. I rememberthe efforts of the late Algernon Ashton,whose claim it was that he had more letterspublished in a greater variety of newspapersand periodicals than anyone else. Purevanity, as one would expect from a manwho, nbt being able to help being christenedwith such an unfortunate christian name.yet used it.

Vain People

(-NNE must expect Algernons to be vainpeople. Retired military officers are not,

I hope, in a similar category, but I woulddraw your attention to a letter which appearsin the Yorkshire Post from Lt. -Col. RaleighChichester -Constable, if you please. This iswhat he says : "When are we to have a taxon bicycles? One of 5s. or 7s. 6d. wouldbring in millions. Why is the user of suchin these days when money is so much neededallowed to go free ? It is a scandal thatsuch should be allowed to continue.' Mr.R. C. Constable as Lt. -Col. has, I assume,been taught arithmetic. If we assume thatthere are 12,000,000 cyclists and the taxwere imposed at 5s., it would yield exactly£3,000,000. Constable's use of the word"millions" might lead readers of the news-paper to suppose that by taxing cyclists weshould be able to abolish the income tax.I advise soldiers, retired choleric colonels,majors, captains, and others, to confinetheir attention to military subjects, andleave cycling matters in the safe hands ofnational organisations such as the C.T.C.They should also read the occasional butpointed letters to the press published abovethe signature of G. FL Stancer, the Secretaryof that organisation.

Summer -time Extended

CUMMER-TIME extends to NovemberJ 16, and so for a few more weeks weshall be able to enjoy the evening rides fora few hours-yes, in spite of the sirens,bombs and anti-aircraft fire. There isnothing so conducive to tranquility of mindas a bicycle ride. When William Willettintroduced the summer -time principle, helittle thought how useful it would be in timeof war. We have accepted the principlethat we can fix our clock according to ourneeds. Cyclists appreciate the idea morethan most. Ours has been one of the fewsports to carry on in spite of the war,increased overtime, seven-day weeks, andlack of training opportunities. There wasa full field of 100 riders in the Finsbury C.C.Open " 25 " which fell to the credit ofPape in 1 hr. 4 mins. 10 secs. The Brent-wood Road Club early in September ranfour events at the Romford FootballGround Track, in spite of the fact that awarning went during the meeting.

The R.R.A. Handbook

I HAVE received from Leonard Ellis,Secretary of the R.R.A., a four -page

leaflet listing the officers elected at the lastA.G.M. in January, and who were appointedfor the duration of the war. The leafletincludes the list of records as from December31, 1935. I have a collection of R.R.A.handbooks, and 1 hope that it will not bemore than a year before the war is over anda new handbook is published. There willnot be attacks on professional recordsduring the war.

October, 1940 THE CYCLIST c39

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c.40 THE CYCLIST October, 1940

NO bicycle can be considered sole unless it is properlybraked, not even the fixed wheel machine. True

enough, in the old days we rode brakeless bicycles andrelied on our muscular power of back pedalling, butthen there were no motor -cars on the roads and theneed for a sudden stoppage seldom arose. Now theminimum braking power should be at least one brakeon a fixed gear machine and two on a free wheel model.

Brakes are made in three types, those operating onthe rims, either by side pressure (caliper brakes) or onthe underside of the rim (pull-up brakes); hub brakes,operating an expanding shoe inside a drum fixed onthe huh; and coaster. brakes (rear wheel only), operatedby foot back pressure on the chain, which expands ametal cone inside the rear hub.

When new, all brakes are effective, even the cheapesttypes, and they would remain effective if care andattention were given to their adjustment. But in99 cases out of a 100 it isn't. The bicycle has becomesuch a common vehicle that it suffers the neglect of allcommon things, even though that neglect imposes acertain amount of risk on the rider.

The commonest form of braking is the roller -levertype rim brake, worked by roller levers runningparallel with the handlebar operating rods attached tothe pull-up stirrups of the brake. 'l'o keep the frontbrake in perfect adjustment is a simple matter, as thepull is a direct one. It is the rear brake that sofrequently suffers from neglect or careless adjustment.The angles of the rod -jointing levers must be keptcorrectly adjusted to the pull if the brake is to retainits power in retardation, and 1 am sorry to say It, butnew folk pay the slightest attention to this importantfeature of proper working, and not all dealers.

Another point is that this type of brake should havethe blocks renewed when they are about half worn downin the shoes, or when the screw adjustment of the rearbrake has been fully expanded to take the block wear.There is then no need for the lever angles of theoperating rods to be upset, and a new pair of blocksis the cheapest and easiest method of retaining brakingpower.

Take Your ChoiceON practically all sports models, the caliper brake

(the side -pressure type) is the fashion. Themechanism of this form of brake is always actuated byBowden cable, so joints and angles are eliminated andadjustment is obtained through a screwed sleeve.

In one form of caliper braking, the cantilever, theoperating cable is divided and the brake shoes do theirwork indepandently and firmly with a gentle handpressure on the actuating lever. But there are manytypes of caliper brakes on the market, and undoubtedlyone of the most popular is the side -pull caliper, withits scissor-like movement clipping the rim, and its neatattachment with one bolt through the crown fork inthe case of the front brake, and the bridge strut on theseat -stay in the ease of the rear brake. These boltsshould always be kept tightly screwed home, for onthem all the braking strain devolves.

Like all machinery, the cable brake needs sometriflin attention by way of lubrication and occasionaladjustment, and, provided it is given such simpleoverlooking, it will render you good service.

The hub brake is the latest enniei in the way ofbicycle retardation, and closely follows the practice ofmotor -cycle and motor -car braking IT was first usedas the retarding power on tandems because the heatingof the rims due to brake pressure on tandem wheelswhen long hills had to be negotiated was se excessivethat burst tyres sometimes resulted, and patches oninner tubes were often lifted under the friction heat.

So a well-known firm designed and marketed a hubbrake for tandem service, and it immediately becamepopular with users of the double seater. The mechan-ism of the hub brake is precisely similar to thatemployed on the motor -cycle brakes, and actuated byBowden cable leading from the usual type of handle-bar lever.

It is a t ,suble-free retarder, which only needsoccasional adjustment, but care should be exercised inoiling the hubs through the usual lubricator by notover -oiling and thus allowing excess oil to percolate to

WAYSIDE THOUGHTSBy F. J. URRY

The Essence of Safety

the brake draws and so seriously reducing brakinge fficieocy.

EvolutionNATURALLY, when the tandem hub brake was so

successful, numerous accessory makers turnedtheir attention to the design of a lighter and smallerpattern for service on singles, and the result to -day iswe have a selection in hub brakes to meet all require-ments. The hub brake is neat and most efficient, butit is heavier than the rim brake and more costly, so isusually found on the better models of roadster bicycles.

The hub brake can be bought and fitted se a separate

One form ofBowden Caliper

brake

unit; it can also be obtained in conjunction with two -speed and three -speed gears.

There is now only one type of make left to mention,the coaster hub, once so popular in this country, andstill retaining its popularity in U.S.A. and on theContinent. Indeed, most of the Continental bicyclesare so equipped, and before the war many of the hubswere supplied by British manufacturers.

As already explained, the coaster is, in its brakingeffect, a metal -to -metal friction clutch never quite

A famous brokeThe Resilion

"Anchor"

clutching. The expansion of the braking cone Isactuated by applying leverage via the chain inthe manner of back-pedalling action. The brakecomes on smoothly when tir necessity of themoment only calls for reduction of speed, but asudden back-pedalling movement may skid the

The Perry hubbrake

rear wheel, so for quick stopping a front rim brakeshould always be used in conjunction with the coaster.

Two- and three -speed gears can-or could-b:obtained with the coaster brake incorporated in theirmanufacture. The great virtue of the coaster is thefact that it is practically foolproof and everlasting.

Be Certain and SafeI one last word on the question of braking. It

has been Said that the man who knowingly uses acar with defective braketi is a potential murderer, 111111should be treated accordingly. I agree; but I alsoagree that the cyclist who rides a defectively brakedbicycle knowingly is a potential suicide and may heworse. There is no excuse for such conduct, for cyclebrakes are simple in construction, easy to adjust, andeven if complete replacement is necessary, they are notcostly.

My outlook on cycling is to be comfortable andsecure. The first I obtain through saddle and gears;the second by the fitment of good brakes and care ofthem during their working life. The result is a con-fidence in cycling that adds a considerable measure toits enjoyment-how much It is difficult to estimate,yet the sense of ease and security is always there whenthe machine is running sweetly and silently and youknow you can Inimediatety check its speed by a fingerpressure on the brake lever. That condition is worthaiffeof trouble to attain and retain, both easilypossible.

1 have said a lot about brakes because of their safetyimportance in the scheme of cycling. Now I want tomention another matter which is far too often a ques-tion of pride over-riding good judgment.

You have seen people struggling up hill, literallystruggling, just because they were too pig-headed toget off and walk and by so doing change the exerciseand actually obtain a rest. Why do we do it? Mainlybecause we imagine the onlooker thinks we cannotride that hill. As a matter of fact, the onlooker, as ageneral rule, has no interest whatever In our perform-.ance, and even if he has, why in heaven's name shouldwe make an uncomfortable effort to mollify or dis-appoint him?

Believe me, I was once just as determined to rideevery activity as the next youth, and probably theviolent exercise did me no harm, but now I am riding abicycle for joy, and when the work of propulsion cancelsout the joy, I take the next best method of continuingthe journey until the road gradient eases.

What, you may ask, about the low gear of the four -speed hub? Well, there comes a hill now and then witha gradient that defeats easy pedalling even with a verylow gear; or it may happen the wind, or your ownmood of idleness or muscular condition, resents theextra pedal pressure needed to sustain equilibrium.Then walk or rest, and you will be a happier cyclistwhen the summit is reached and you are in the saddleonce more.

Remember, a bicycle is not like a pair or rollerskates. You haven't got to take it off and carry it,and then fasten It on again; you just quietly push it tothe top of the hill, cock your leg over the saddle, andare away again without any trouble.

If you are riding with a companion, then make yourspeed to fit his comfort, or if the boot is on the otherleg, tell him quite frankly such is your comfortablegait and, if he must hurry, then the road is equallyhis property. lots of people have been wearied ofcycling because the urge of companions has speededthem beyond,their comfortable capacity. Do not falla victim to such thoughtless kindness; you are thecaptain of your speed, and yours is the engine -room.

The Stormer) Archerhuh brake dismantled

October. 1940 THE CYCLIST e41

"CANTILEVERS" -THE PROOFWrite for a free copy of

an illustrated booklet.

" CANTILEVERS " costI2/- each, front or rearin nickel or enamel finish.Chromium Plated, 14/,For Tandems, I3/- each,front or rear (chrome, 15/-)

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We claim that " CANTILEVER Cycle Brakes are the finest on earth. In order togive proof positive of our assertions we instituted a series of tests to show thestopping power of " Cantilever " Brakes. A rider weighing 111 stones wasdespatched down a steep slope travelling at 16 miles per hour. At a given signala 6 lb. pressure was applied to one lever. The machine was brought to a standstillin 20 yards. Other tests carried out at the same time in the presence of several ofthe leading figures in the cycling world showed that other types of brakes required334 yards to achieve a similar result.

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c.42 THE CYCLIST October, 1940

My Point of ViewBy " WAYFARER "

Cycling will Help you to Fo-ge' the 'WarTHESE are indeed halcyon days from the cycling1 standpoint. It is true that a grim shadow hangs

over our lovely country, but there is no doubt in mymind that it is going to be dispersed-and dispersed inthe only way which will ensure to us, and to those whocome after us, a continuance of the abiding freedomand security won for us by our forbears. The geniusof our people, who hold in constant remembrance ourhigh traditions, will triumph, and we shall return toour essentially peaceful mode of life.

But, if you want to get right away, momentarily,from that grim shadow, and from all the dread possi-bilities which " total " war connotes, take your bicycleand go out into the country. Such a country it istoo ! Seek the seclusion of the lanes. Pedal serenelyalong, now taking this turn to the right, now this oneto the left : here riding through a water -splash, therefinding that you have finished up in a farmyard andmust retrace your steps; now pausing to absorb adelicate view and anon loitering in a delectable woodlandHow good-how very good-it all is, to be sureIndeed, there is nothing like it, and the gifts named,together with a hundred others, are secured at aninfinitesimal cost, for the price of running a bicycle isa fraction of one penny a mile.

When appetite reminds you that it is meal -time,look out for a typical cyclist's house of call, and therehave a good tuck -in, resuming your journey before themoment comes for the B.B.C. to remind you that" there's a war on." So continue your ride until youhave completely forgotten the war-until you aresaturated with happiness-until you realise anew howeasy it is to get away from the things that worry.And then make your way placidly homewards, withmind soothed and healed, and with a new outlook-aserene and joyous outlook-on life ; with your store ofoptimism and philosophy re-established and with athankful heart to " whatever gods there be " for thecreation of the handiest travel -instrument the worldhas ever known-the little old bicycle-the despisedand condemned bicycle, which, all the same, was oneof the really great creations of the Victorian era.

Very, Very GoodYES, they are halcyon days for us who remain loyalto the bicycle, or who, by the necessity of the times,

have " returned to the fold." (I have had 50 years ofthe game, and I seek no other, becausr,, for one thing,I always like to have the best !) The absence of sign-posts and mile -stones adds a new difficulty and a newpiquancy to cycling. One realises now what jolly oldpals these roadside features were --especially the sign-posts. However familiar the highway, one looked upto the sign -post as it slid by and read for the thousandthtime the old accustomed message. Now the sign -post,like the mile -stone, stands in its place stark anddumb; it has no word for us; it has ceased to be onspeaking terms with passers-by, and we are ignored.Incidentally, since the sudden panic about " FifthColumnists (a euphemism for " traitors ") startedrampaging, I have come across only one active sign-post, and I thought that its message was extremelysignificant from the parachutist point of view. It said,"To the Cemetery " May it be a true word for those,from within or without, who would savage our country.

Then the need for displaying one's identity card topersons with a right to see it sometimes adds a humor-ous touch to one's cycling. On a recent evening, as Iwas dragging my reluctant card from its lair, a jocularpoliceman told me. that a card he examined a fewminutes earlier contained a ten -shilling note. " Well,"I retorted, " if you can find a ten -bob note in my card,

we'll share it-and I'll have my five shillings at once ! "At the same very point, a week later, I found the policeon the job again, and I quietly came to a standstill inorder to oblige. Then the " special " on duty wavedme on, saying, " It's all right, Mr. Urry; I recogniseyou." Which was rather clever of him, because Ihappen not to be Mr. Urry, nor am I at all like him.But I was not prepared to have a bother with the" special " on those flimsy grounds, and I went on myway without displaying my card.

The Humorous SiderN another day, being in some little doubt as to my-., whereabouts, 1 made inquiry of a lady who wasindulging in the pleasant task (at which I could bevery good !) of leaning on the gate to her front gardenat a country cottage. She at once gave me theinformation I wanted, and then she was assailed by aperfectly hideous thought, which she voiced thus : " Isuppose that I. ought really to ask you to show meyour identity card." My reply was in these terms :" If you did, I would say that you had no right to seeit, and then you-quite rightly-would refuse to giveme any information. So what are you going to doabout it? " Then we both laughed, and 1 resumedmy journey.

Back to Tea PlacesLET me revert for a moment to the matter of forget-

ting the war. This process is markedly aided bysome of the rest -houses at which I call, the quantity offood supplied, and the price charged, causing you todecide that Hitler is just a bad-a very bad-dream.Believe it mr,not, it is still possible to obtain shillingteas comprised of first-class food (I have little use forany other), with cakes galore and with overflowingsugar basins, and without any sign of the rationing ofbutter and tea. Really, you begin to doubt this warbusiness. True, one of my favourite caterers hastemporarily thrown in her hand owing (so she says) tothe difficulty of obtaining supplies. The Food Officetold her bluntly (so she says) that they were going todo their best to prevent cyclists obtaining extrarations by going out for meals. I can hardly believethat this is anything like a literal record, of what theNabobs said to my friend, and my incredulity is sup-ported by the circumstance that at another tea place,a couple of miles away, the tables are groaning underthe weight of food. Possibly the approach to theNabobs of the first caterer mentioned was not quite astactful as that of the other caterer. You can get somuch by going the right way about it !

ITEMS OF NEWSThe well-known cycling enthusia5t of Nottingham,

Wilson Barratt, has received his papers and is joiningthe Navy within the next two weeks. He has recentlybeen very active in connection with the N.C.U. SpitfireFund and has been the means of raising a fairly largesum of money and obtaining much recognition for theFund in Nottingham and District. We are sure hismany friends will wish hint a speedy return to peace-time activities. .

N.C.U. Affiliated Clubs in the Surrey Centre shouldnote that with further notice, enquiries of everydescription should be addressed to The Secretary,National Cyclists Union, 35, Doughty Street, W.C.1,as the immediate acting officials in the Surrey Centrehave been called to the colours.

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

NEW CYCLESHOBBS OF BARBICAN, manufacturers of modern

frames, cycles, tandems and tricycles. Special-ists in frame design. Lists and individual quota-tions free. Personal attention to every order. -34,Barbican, London, E.C.1.GroseSpur All British Cycles, 75s. Art List 100models free.-Grose, Ludgate Circus, London.

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

catalogue free.-Idle Road, Bradford, Yorks.

ACCESSORIESGEORGE GROSE, the best house for all cycle

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

CAMPING EQUIPMENTCAMOUFLAGE your tent by brushing on

Granger's Solution Camobrown and Camogreen,which will waterproof and preserve it withoutstiffening. ls. 9d., 3s., 5s. 6d.; 1 gallon, 10s. 6d.,treats 240 square feet of 6 oz. canvas. From Scoutand Guide shops, camping outfitters. Halfords andstores.

INSURANCEASK your dealer for one of our Insurance Certifi-

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

TYRES

1VTYRECleranebet makes,10,000

33(% off standard prices. Carriagepaid. Price List on application.-Davies, TyreFactory, Wednesbury.

WIRELESSCRYSTAL SETS KITS, complete, 5/11d., post

free.-W. J. Buckle, 63 Avenue Approach, BurySt. Edmunds.

A Grand New Sudden Story !

SUDDENTAKES THE TRAIL.

A pulse -stirring red-blooded "Western,"telling of " Sudden," the lone cowboy.7/6 net of all Booksellers, or 8/- by postfrom George Newnes, Ltd. (Book Dept.),Tower House, Southampton Street,London, W.C.2. Ask for it at libraries.

THE CYCLOMETERMANUFACTURERS

Standard Model - 2'11 eachDe Luxe Model - 3 6 eachTo Fit 24", 26" or 28' Wheels.

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BRITISHMADE

William Kept His End Up !The merits and demerits of this or that riding position werejust as hotly disputed in 1066 as they are to -day. William,for instance, maintaining that every true knight of the road

should adopt a " recumbent posture."

111111 sTHE Coquet -oil. OF

TRANSMISSION TROUBLES

Though, to -day, no two cyclistsmay agree on the subject,there's one point on whichALL riders are unanimous-aWILLIAMS Chainwheel givesthe best results with ANYriding position.

EDWARD WILLIAMS - FOUNDRY LANE - BIRMINGHAM

BUY, EXCHANGE OR SELLAdvertisements 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 2i % 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.

LITERATURE

160 PAGES ILLUSTRATED REVISED WORK-SHOP HINTS and Calculations in Calvert's Mechanics'Handbook, 8d., post free.-Sherratt & Hughes,St. Ann Press. Park Road. Timperlev, Ches.

A HANDY BOOK FOR RADIO ENGINEERS."The Radio Engineer's Vest -Pocket Book," by F. J.Camm, contains in easily consultable form nearlyevery fact, figures and formula which service engineers,students, circuit -designers, radio -operators, trans-mitters, constructors and manufacturers require.Fully indexed. Ot all booksellers, 3/6 net or by post3/9d. from George Newnes, Ltd. (Book Dept.), TowerHouse, Southampton Street, Strand, London, W.C.2.

"DIESEL VEHICLES: Operation, Maintenanceand Repair," edited by F. J. Camm, is an importantbook for the rapidly -growing army of diesel roadvehicle users. Of all booksellers, 5/- net, or by post5/6d. from George Newnes, Ltd. (Book Dept.), TowerHouse, Southampton Street, Strand, London, W.C.2.

" Baker's" Sold2rine. For allelectrical work and whereverpaste flux is preferred. Popularsizes include: 2 oz. tins 6d.; 4 oz.tins 8d. Also supplied in bulk.Obtainable from allwholesalers 1,

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OUR ADVICE BUREAU

COUPONThis coupon is available until Oct. 31st., 1940,and must be attached to all letters containingqueries, together with 3 penny stamps. A stamped

addressed envelope must also be enclosed.PRACTICAL MECHANIC:, our. 1940.

MUSICAL INSTRUMENTS

BAND GUIDE. Hints on the Bugle, Drum, Flute,Staff Parade formation, etc. Free, post paid.-Potter's (Manufacturers), West Street, London, W.C.Z.

TOOLS

GRAYSON'S Glass -boring Outfits and Tub(Cutters avoid risk.-Below.

DRILLS, Taps, Dies,. Files, Chisels and PunchesBest quality at keenest prices.-Grayson & Company300 Campo Lane, Sheffield.

BRAND NEW POWER TOOLS of quality10 -inch handsaws, 54s.; Jigsaws, 22s. 6d.; Bench

Ils.; Circular Saws from 25s.; 3 -inch S.0toolroom Lathes, front £4 5s. New 1 -inch chromiumplated Micrometers, 12s. 6d.; Electric Drills, 37s. 6dGrinders.-John P. Steel, Bingley.

MYFORD LATHES have no equal. Real precisionlob. Lists tree, delivery anywhere. Terms still avail-able. Your lathe taken in part exchange. Nuttall's,20, Albert Street, Mansfield.

Machine Vices, 21" Jaws, 1" Deep, opens 34."; completesets of parts, only require drilling and tapping,3/9 set. Burke.

400 Genuine Carborundum Wheels. Ii" Wide, 1" Hole,5" Diam., 1/0; 5a" to 6', 2 ni" to 7", 3/6. Burke.

2,000 Small High-speed Twist Drills, .020" to .065", 2/ -per doz. Burke.

31- any Lot. SEVEN LOTS £1

Doz. Ass. Whit. & B.A. Taps, to Dian'. .ILH.

20 Ass. Ditto, Lett -hand, to f'f" Dian'.

1" Sq. Toolholder with Four H.S. Tools.

Eight Assorted H.S. Tools tor Above.

" to f" Silver Steel. 13 pieces, 13" long, Precision -ground to size.

r to r Silver Steel, 4 lbs., 2" to 4" Long.

4" to I I" Silver Steel, 6 lbs., II" to 3" Long.

4" to L" super High-speed Steel, Precision -ground,6' Ass., 2" to 3" Loin.

500 Ass. Brass and Steel -plated Screws, etc.; B.A.Fine Threads, to 1".

100 Bright Hex. Bolts with Nuts, to 1" Liam., to 3"Long. Surprising Value.

12 Ass. Fine Thread Taps, j" to 1" Diam.

Three Doz. Tungsten Hack -saw Blades, any size. 9":10"; 12".

18 Grinding Wheels. r to 1" Diam., suitable forFlexible Shalt use.

Three H.S. Ton or Reamer Fluting Cutters, if"i" lisle. Worth 6 - each.

15 ass. Files, 4 to Handy variety.

12 ass. Toolmakers' Needle Files. Indispensable.

12 ass. Carborundum and Fine Emery Wheels, r to1" Thick, 2" to 4" Diam.. all i" Hole.

3 lbs. Best Blue Twill Emery Cloth Strips, r to 2"Wide; ass. Superthw to Coarse.

11 orders Carr. Paid except abroad.

J BURKE, 41, SUNNYVALE ROAD, SHEFFIELD.

(Dept. 58),

MISCELLANEOUS

BUILD YOUR OWN WIND CHARGER andmake free electricity. Drawings and instructions, 2s. 6d.-Pearse, Middle Taphouse, Liskeard, Cornwall.

TELESCOPES, MICROSCOPES, Scientificinstruments, etc. Send for lists. Sale or Exchange.-C. V. Bolton, F.S.M.C., 49a Leigh Road, Leigh, Lancs.

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A GOOD PIANIST ISALWAYS WELCOMEThere is a way to become a really FINEPIANIST and SIGHT HEADER. I will MastYOU quickly and enjoyably BY POST, fromordinary musk (no freakish methods) enablingyou to read and play at sight any standardrunsicai composition so that you shall give

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in. Whitworth.

POWERFUL12 volt A.C. D.C.

MOTORSat a very keen priceCommutator type,Overall measure-ments (excludingshaft) 2% x x2% in. Wei .Mt 2 lb.

Shunt wound, but can easilyaltered to series, then

40

Vhoilntse.

operates on 30-

Bordon Tube TypePost 7d.

PRESSUREGAUGES

Calibrated to 101b.per square inch butcan be calibrated toapproximatelydouble this pres-sure.Amazing 2t.,, Post5d.

value.

6/6

\ BLACK &DECKERVALVE TESTER

High -SpeedELECTRIC

HAND -DRILLSA high-grade tool with exceptionally fastpenetrative power. Takes up to t/4 -in.drill. Gamages' price is substantiallylower than that asked for similar drillselsewhere. Complete with good _length offlex. For 200/240 volt - -

A.C. or D.C.Please state voltage when

ordering.

BOXES OF TWELVEASSORTED FILES

'The best and cheapest way to buy Files. Bri -

quality. Sizes 6-12 in. 12 for 5/6I tish made and excel len -+

Also sizes 4 to 8 in.,12 for 3/3. Post 7d. Post 9d.

SUPER DOUBLE -SIDED WORK BENCHES

To -day's Value £10Carriage Forward outside our delivery area.

at POUNDS below to -day's valueThese are exceptionally strong and very rigid. Fittedwith two " Record " 7 in. vices (one either side) 2 in.thick, solid English beech top. Smooth clean finish. Extraheavy deal underparts. Fitted two bench stops, two largetool racks (one at each end). All parts exceptionally heavyand bolted together. Bolt heads are sunk and pelletted.A bargain not to be missed.

4 ft. 6 ins. long2 ft. 6 ins. high E61 I 7162 ft. 3 ins. wide

GAMAGES, HOLBORN, LONDON, E.C.1 'Phone your order: HOLborn 8484 City Branch : 107 Cheapside, E.0 2

'14

Published about the 30th of each month by GEORGE NEWNES, LIMITED, Tower House, Southampton Street, Strand, London, W.C.2, and Printedin England by THE SUN ENGRAVING CO., LTD., London and Watford, Herts. Sole Agents for Australia and New Zealand-Gordon & Gotch, Ltd. Sole Agentsfor South Africa-Central News Agency, Ltd. Subscription Rates : Inland and Abroad, 9s. 66/. per annum. Canada, 9s. per annum. Registered at the G.P.O.

for transmission by Canadian Magazine Post.

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ANTI AIRCRAFT AND BREN GUNS - WorldRadioHistory.Com · 2020. 4. 18. · THE FLUXITE GUN is always ready to put Fluzite on the sol-dering job instantly. A little pressure places the