The Scientific Publications of Henry Kater

The Scientific Publications of Henry Kater

GORDON JONES*

Henry Kater was born on 16 April 1777 and died on 26 April 1835. Biographical information about him is not lacking and we need only state briefly that as a young lieutenant of the 12th regiment he assisted Lambton in the early stages of the geodetic survey in India but was forced to return to England in 1806 because of ill-health. After a short time in the senior department of the Royal Military College, Sandhurst, he quali- fied to serve on the general staff and spent the rest of his army career in Britain, retiring (as captain) on half-pay in the reductions of 18 14. On December 15 of this same year he was elected a fellow of the Royal Society and for the rest of his life he devoted his energies to scientific pursuits. His election as treasurer of the Royal Society from 1827 to 1833 seems perhaps a doubtful honour in view of the contemporary criticisms and controversies relating to the administration of the Societyz but Kater was not the target of criticism. The numerous honours received from foreign scientific societies were evidence of his high standing in scientific circles.

Kater is best remembered for the reversible pendulum which bears his name but he did write on other subjects. These were primarily concerned with scientific instruments and accurate measurement, notably the construction of standards of length. This will readily be seen from the list of his publications given on page 184. The roughly chronological order of the list will be followed below in commenting on the publications3.

Publications

1. Description of a very sensible hygrometer. (1 807) and

2. Description of an improved hygrometer. (1 807)

History of Science Department, University of Aarhus, Denmark

Cenlovrw 1965: vol. 11: no. 3: pp. 152-189

The Scientific Publications of Henry Kater 153

These first two papers, written when Kater was 30 years old, describe his use of a type of grass (Andropogon Contortum), which he found in India, to indicate the hygrometric state of the atmosphere.

In the first model the twisted beard of the grass seed, in changing conditions of humidity, turns a small wheel about a horizontal axis and a string passing over the wheel raises or lowers a weight on a vertical scale. In the improved model the torque is applied to a pointer on a circular scale and the number of revolutions of the pointer is indicated by a weighted loop of wire which moves along a screw thread on the horizontal axis of rotation of the pointer. The automatic counting of the revolutions is very important since between the extremes of humidity the pointer can revolve eleven or twelve times. This, Kater points out, is considerably more sensitive than other hygrometers of the time.

His interest in the hygrometer is not casual but is intended to connect with the geodetical work in progress:

“. . . it appears very probable, that this instrument has more to do with the phenomena of refraction, than either the barometer or thermo- meter. . . perhaps some law might be discovered, which might enable us to ascertain the quantity of the effect of moisture on refraction. It was with this view the hygrometer. . . was constructed.. .” The two papers appeared soon after one another in Asiatic Researches

for 1807 and the second was reprinted in the same year in Philosophical Magazine‘ with an introductory note that the “improved model” was being produced commercially in London. Two years later the paper appeared again, taken from Asiatic Researches, in Nicholson’s Journal5.

3 . Description of a new compensation pendulum. (1 808)

The third of Kater’s early papers again attacks a practical problem connected with his work, the temperature compensation of pendulums. After pointing out the disadvantages of the “grid-iron’’ and “mercurial” pendulums when fine adjustment is required he describes “a pendulum, which should unite simplicity and cheapness with the capability of being easily and accurately adjusted.”

This instrument is made from a rod of wood (deal), treated so as to overcome the effects of moisture and suspended from a steel clock-spring. Compensation can be effected by adjusting either the centre of suspension or the centre of oscillation. In both cases a tube of zinc enclos-

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154 Gordon lones

ing a portion of the pendulum rod is employed. The lower end of this tube is fixed either to the support or to the lower end of the pendulum. In the first case, expansion of the zinc draws the clock-spring up through the fixed “cock” of the clock, so adjusting the centre of suspension. In the second, expansion of the zinc raises the weight of the pendulum, so adjusting the centre of oscillation. If the length of the zinc tube is chosen correctly the distance between these two points is constant.

In both cases fine screws are incorporated to adjust the relative placing of the zinc tube and the pendulum. Herein lies Kater’s claim to “easy and accurate adjustment”. As with the hygrometer, the details and method of construction are cleary stated and the relative merits of the two variations are briefly considered. A final note indicates that Kater has not had the opportunity of testing accurately the constancy of the pendulum so compensated.

4. On the light of the Cassegrainian telescope, compared with that of the Gregorian. (1 8 13)

“The Cassegrainian telescope from its invention to the present time, has generally been considered to be merely the Gregorian disguised, and to possess no other advantages over it than the capability of being made shorter with the same magnifying power. This opinion, joined to the inconvenience of its inverting the object, has caused it to be thrown aside, perhaps too hastily, and without a sufficient examination of its properties.” Kater, in these opening words of his first paper in Philosophical Trans-

actions, sums up the position concerning these two types of reflecting telescopes, as he finds it. On testing a Cassegrainian instrument in comparison with a similarly constructed Gregorian of nearly equal ma@- fying power he has found that the former gives a strikingly brighter image. This lead to a quantitative investigation by varying the aperture of the Cassegrainian and judging when the images of an illuminated card appeared equally bright through both telescopes. Kater adds that “of this, the eye judges most accurately.” The results are decidedly in favour of the Cassegrainian.

The essential difference in the constructions is noted by Kater to, be that the Cassegrainian causes the second reflection to occur before the rays reflected from the large mirror have come to a focus. Thus he is


lead to the conjecture that “if light be supposed to consist of particles of matter, is it not possible that these particles, crossing in the same point, may interfere with each other? or , when thus forced within a certain distance of each other, may not a power of repulsion exist, that would occasion many of them to be dissipated?”

The paper is dated Ipswich, 12 April 1 8 13.

5 . Further experiments on the light of the Cassegrainian telescope compared with that of the Gregorian. (1814)

Kater follows up the previous paper with more confirmatory results, dated Ipswich, 1 6 July 1 8 13. A postscript is added giving two quotations from Brewster’s Philosophical Znstruments indicating that he has found better definition before focussing of light than after, a somewhat ana- logous effect. On page 234 we find the beginning of an appendix dated London 20

April 18 14 which records experiments with a single mirror “to decide, in a direct manner, whether any rays are Iost in crossing each other at the place where an image is formed.” A long series of varying experiments is described whose results all more or less confirm the originals, even though eight different observers were used. Spherical aberration is not mentioned although Ramsden has pointed out6 in 1779 that the Cassegrainian telescope could better correct for aberration than the Gregorian.

6. Facts and remarks, upon the interruption which the situation of the maintaining weight produces in the rate of a clock, when near the pendulum. (1 8 13)

This letter to Nicholson is dated Ipswich 6 December 1812, and is signed “.HK.”

In Nicholson’s Journal of October 1812 Thomas Reid has recorded an effect observed in a clock pendulum, “that of the arc of vibration becoming less when the weight is near the ball of the pendulum.” Reid has attributed this to attraction between the weight and the ball of the pendulum but Kater points out that attraction would seem to have an effect which cancels out in a complete oscillation. More likely is the explanation given by “the late Dr. Hornsby. . . who. . . attributed it to the in-

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creased resistance of the air, from its free motion being impeded by the weight of the clock.” Kater might also have mentioned that much the same effect was noted by Newton’ in his discussion of a pendulum moving in a resisting medium:

“. . . I found.. . that the resistance in the water was augmented. . . In searching after the cause I thought. . . that the vessel by its narrow- ness obstructed the motion of the water as it yielded to the oscillating globe.”

It is interesting to note that Kater here speaks of “motion of the air.” In his later pendulum experiments he assumes that besides buoyancy the only effect of an atmosphere on a moving pendulum is frictional, causing a reducing amplitude, but otherwise having no effect on the period of oscillation. He had thought to investigate the inertial effect of the dis- placed air he would have found otherwise. Again we have from Newton?

“But the time of the oscillations, both short and long, seems to be prolonged in some measure by the motion of the medium . . . it resists the pendulums in their descent more, and in their ascent less, than in propor- tion to the velocity; and these two causes concurring prolong the time.” Although this effect was generally considered in Kater’s time to be neg- ligibly small it was later pointed out by B d y 9 that literature on the topic had, in fact, been available since 1786 when du Buat had included in his Principes d‘Hydruulique a section with experimental results on Mesure de la portion de fluide qui accompagne un corps en mouvement duns un fluide indbfini.

7 . An improved method of dividing astronomical circles and other instruments. (1 8 14)

The exact subdivision of a circular arc was one of the trickiest problems which faced an early instrument-maker. The use of instruments (like the beam compass) in contact with the metal surface required great skill because of the danger of deforming reference points. This had led to the use of optical methods, one of which is described by Troughton in Philosophical Transactions for 1 809lO.

The circle was first engraved and the approximate positions of the scale divisions marked by dots against the appropriate number. These dots were then examined by viewing two dots at the ends of a diameter by fixed microscopes and then again after turning the circle through 180.O. The error of each dot was calculated and the accurate position marked.


Kater’s paper, dated London, January 1814, is one of the suggested improvements to Troughton’s method. Instead of marking erroneous dots on the scale, Kater uses small devices which themselves carry movable dots and can be clamped to the edge of the circle in different positions. The “adjustable dots” are examined by microscope almost as in Trough- ton’s method and adjusted so as to divide the circle into the required number of parts. Only then are the dots marked on the scale itself. The design of the apparatus and the method of using it are Kater’s own but he notes that “in the essential principle on which this method is founded, I find that I have been anticipated by the Duc de Chaulnes; but some parts of the apparatus which he has described are so complicated, and others so incapable of the necessary adjustments, that his method of dividing never has been, nor ever can be introduced into practice, and indeed was intended by its author merely to form a model, which was to be employed as part of a dividing engine“”.

In the construction of the mural circle of the Armagh Observatory the divisions were applied %y a method scarcely differing from that proposed by Captain Kater”I2.

8. An account of experiments for determining the length of the pendulum vibrating seconds in the latitude of London. (1 8 18)

This, Kater’s best known paper, is the first of a trio of papers which appeared in Philosophical Transactions in the period 18 18-1 8 19. These form a record of the work undertaken by Kater in connection with the intended definition of the national standard of length in terms of a natural constant. In the paper of 18 19 Kater writes of the formation of the “Pendulum Committee”.

‘‘. . . an Address was presented to His Royal Highness the Prince Re- gent, in pursuance of a resolution of the House of Commons of the 15th of March 18 16, to the following effect.

“Resolved, that an humble address be presented to His Royal High- ness the Prince Regent, that he will be graciously pleased to give directions for ascertaining the length of the pendulum vibrating seconds of time in the latitude of London, as compared with the standard measure in the possession of this house, and for determining the variations in length of the said pendulum, at the principal stations of the Trigonometrical Survey extended through Great Britain; and also for comparing the said standard measures, with the ten mil-

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lionth part of the quadrant of the meridian, now used as the basis of linear measure on (a part of) the continent of Europe.” In consequence of His Royal Highness’s compliance with the prayer

of this Address, an application was made by His Majesty’s Ministers to the Right Honourable Sir Joseph Banks, requesting that the Royal So- ciety would be pleased to afford all the assistance in their power for the accomplishment of the objects therein mentioned; and a Committee was appointed for that purpose, of which I was named a member.”

Thus Kater, to whom the practical execution of these directions was entrusted, had three distinct tasks, each of which received its appropriate report. The work reported forms links in two long chains of investigation; the study of the pendulum and its use in determining the acceleration due to gravity and the figure of the earth”, and the standardisation of weights and measures14.

At the opening of this first paper, dated London, July 1817, Kater refers briefly to the difficulty involved in measuring the length of a simple pendulum and how he intends to overcome this by using a pendulum with two parallel knife-edges, one at the centre of suspension and the other at the centre of oscillation. When the pendulum can be swung on either of these without altering the periodic time the distance between them, measured in a straight line through the centre of gravity, is, from HuygenslS, the length of the equivalent mathematical pendulum. Kater had, in fact, been anticipated in his idea of determining the length of the seconds pendulum by using Huygens theorem16 but he appears to have thought of the idea independently and was undoubtedly the first to put it into practice.

After a fairly detailed description of the pendulum, supplemented by diagrams, Kater describes a long series of experiments at the home of Thomas Browne in Portland Place during June and July of 1817. In these the pendulum is swung from both knife-edges and the distriiu- tion of its weight adjusted so that the periodic time for each is the same. The distance between the knife-edges is measured optically with micrometer apparatus and having applied corrections for temperature, buoyancy of the atmosphere, height above sea-level, amplitude of arc, and having checked that the support is firm and the knife-edges in good condition, Kater assumes that he has the accurate length of a pendulum and its accurate periodic time. From this he calculates the length of the pendulum vibrating seconds at sea-level, in a vacuum, at 62” Fahenheit, and quotes the latitude at which the experiments were carried out. The result


is complicated, however, since in measuring the length of the pendulum it has to be compared with the standard in the possession of the House of Commons. This probably meant Bird’s Parliamentary Standard of 1758, or possibly the copy of it from 1760. These, examined by Sir George Shuckburgh in 179817, were both in the possession of the House, but neither of them was the legal standard. Moreover, Kater states that “the standard yard made by Bird in 1758, for the House of Commons . . . is little adapted for measurements where great precision is necessary.” He does, however, give a value for the length of the pendulum in terms of this standard, determined by the mean of a number of bisections of the large dots. For the main scale he prefers that made by Troughton for Sir George Shuckburgh. This is the one compared directly with the pendulum. A third value is given in terms of General Roy’s scale which “formed the basis of the Trigonometrical Survey of the kingdom.”

For this work Kater was awarded the Royal Society’s Copley Medal for 18 17. The results were, however, to have a very short life since the corrections were soon queriedl8. The major error was pointed out by Bessel in 182619. He found that in the correction for the presence of an atmosphere the dynamic as well as the static effect of the surrounding air must be taken into account. Thus, Kater’s correction was too small and, since the “dynamic” correction was dependent on the shape of the pendulum, the pendulum was not truly reversible.

An appendix is added to the paper. It contains a letter from Young to Kater giving comments on, among other things, Laplace’s demonstration that even if the knife-edges are not sharp, but considered as cylin- ders, the length of the equivalent mathematical pendulum is st i l l the distance between the extremities of the knife-edges to a high degree of accuracy.

9. On the length of the French mLtre estimated in parts of the English standard. (1 8 1 8)

The apparatus Kater uses in this comparison is the same as that used in the pendulum experiments - a bar carrying adjustable micrometer microscopes - and is similar to that described by Sir George Sh~ckburgh’~. The metres used were first compared with a standard metre by Arago in Paris and then sent to Kater in London. One is an end-standard, the other a line-standard.

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The line-standard is compared with little difficulty with the same divisions of Sir George Shuckburgh’s scale as were used to find the length of the pendulum. The end-standard presents considerable difficulties, but is successfully compared using a method Kater found useful in measuring the distance between the knife-edges of the pendulum. Precise rectangular blocks of brass are made and lines are engraved on them, parallel with, and close to the edges. The distance between these lines is measured when the blocks are in contact and when they are separated by the end-standard. In both cases temperature is measured and corrected for. The paper is dated London, November 18 17.

10. An account of experiments for determining the variation in the length of the pendulum vibrating seconds, at the principal stations of the Trigonometrical Survey of Great Britain. (1 8 19)

The last of the trio of reports, almost 200 pages long, constitutes Part 3 of the Philosophical Transactions of 1819. It is dated London, June 1819 and describes the experiments carried out at the seven stations of the Trigonometrical Survey known as Unst, Portsoy, k i t h Fort, Clifton, Arbury Hill, London and Shanklin Farm. Since the measurements are only to be relative the pendulum is an “invariable” type, having only one knife-edge. This type of pendulum was to become widely used in the many voyages of exploration embarked upon in succeeding years.

The procedure of the experiments is very similar to that described in the previous paper on pendulum experiments in London but much more information is added about the positioning and fixing of the pendulum support at the various stations. In addition, there is much on the astronomical observations used to check the pendulum clock with which the accurate time period was measured. The results are again given as the number of vibrations in a mean solar day and corrected for temperature, amplitude of arc, buoyancy and height above sea-level. The latitude of each station is carefully measured, particularly where Colonel Mudge’s results were anomo1ousZo, but little deviation is found.

The final discussion is of the ellipticity of the earth, calculated from the experimental results. This emphasises the dual nature of the experiments. Although it is not stated in the directions there was an intention to measure, in effect, the absolute value of the acceleration due to gravity in London and relative values throughout Great Britain to be compared

The Scientific Publications o f Henry Kater 161

with French observations2’ and from which it was hoped to gain information on the earth’s form. Kater uses Clairault’s expression to calculate the ellipticity for every pair of stations, giving the results in a table on page 423. In discussing the results, which are widely scattered, he says:

“It must be evident that nothing very decisive respecting the general ellipticity of the meridian can be deduced from the present experiments. For this purpose it is requisite that the extreme stations should comprise an arc of sufficient length to render the effect of irregular local attraction insensible; and this effect might be diminished, if not wholly prevented by selecting stations of similar geological character, and which should differ as little as possible in elevation above the sea.”

Kater sees the liminations of the method but another remark of his indicates that he can also see the possibilities:

“. , . in passing through a country composed of materials of various densities the pendulum may be expected to indicate such variations with considerable precision.”

Both pendulum papers were widely quoted in contemporary periodi- calszz.

11. Instructions for the adjustments and use of the instruments intended for the Northern expeditions. (1 8 18)

The voyages of exploration to the Arctic proposed by the Admiralty in 1817 provided an opportunity to extend pendulum observations. These and other scientific measurements were planned by the same committee (the Pendulum Committee) as was appointed to effect the measurement of the seconds pendulum.

All the instructions are contained in 38 pages, of which Kate>r wrote the first 28, giving “directions for the use of the instruments executed under his superintendence”. The observations required from the pendulum experiments are similar to those which Kater himself made with a similar pendulum in the British Isles during the same periodu. In addition to the discussion of the pendulum experiments and the astronomical and time-keeping instruments connected with them Kater also describes the instruments for magnetic observations. The magnetic inclination is to be found from the dipping needle and the magnetic intensity is obtained from the time of vibration of the same. “Capt. Kater‘s Azimuth Com- pass” receives a brief description and some instructions for its use. Sabine,

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who was to carry out the observations on the voyage in search of the North-West passage, quotes the description in his reportz4 and notes the extremely disturbing effect of the ship’s iron on the corn passe^^^. Perhaps this is the reason why Kater remarks that “of all instruments known, the common azimuth compass is perhaps the most defective”. Kater’s compass figures again in his obituary notice’:

“. . . This instrument is the more valuable from being fitted with a sight, on which slides . . . the segment of a glass cylinder . . . by means of which a fine line of light is thrown on the index, and may be seen at the same time as the graduations on the card. This ingenious and simple application appears to have been known to Halley, and is indeed described by the celebrated Godfrey of Philadelphia; yet it has been suffered to be forgotten for more than a hundred years.”

The last instrument discussed by Kater is the constant displacement hydrometer used to determine the specific gravity of sea-water in different latitudes and at different depths.

Three sections of the instructions remain. Wollaston writes on the dip micrometer, dip sector and macrometer; H.D. (Humphrey Davy) writes on the use of electrical instruments and the possible existence of electric poles on the earth, on taking up sea-water from a given depth and on the expected atmospheric phenomena; instructions are given for the use of Sir Henry Englefield‘s barometer.

12. An account of the comparison of various British standards of linear measure. (1 821)

Although Kater finished his pendulum experiments in 18 19 he was still involved in the discussions on weights and measures because the House of Commons ordered yet another inquiry into the still very uncertain subject. This uncertainty may be seen in the recommandations of the three reports issued by the Commission of Inquiry on 24 June 1819, 13 July 1820, and 31 March 1821. Apart from the changes in the value of the length of the seconds pendulum made following the criticisms of the corrections originally employed18 there was the difficulty of choos- ing which of the various standards of length and mass were most suitable as basic standards.

The first of the reports mentioned above recommended General Roy’s standard for the legal determination of the standard yard since it was used in the measurement of the base of the Trigonometrical Survey in


178426. But in this paper Kater records discrepancies he has found in the various scales used to lay down and to remeasure the base, even though their agreement was reported to be good. He proceeds to examine the best standards of the time and his results, given on page 91, cause the recommendation of the Commission to change.

‘The standard used in the Trigonometrical Survey being thus unex- pectedly found to differ so considerably from every other standard of authority, the Commissioners of Weights and Measures proposed in their Second Report, that Bird‘s Parliamentary standard of 1760 should be considered as the foundation of all legal weights and measures.”

The advantage in this choice was stated to be that the standard could be “considered as perfectly identical” with that of Sir George Shuck- burgh which had been compared directly with the metre and the seconds pendulum; but Baily had much to say on the wisdom of this choice2’ because the chosen standard was a copy of the one Kater has described as “little adapted for measurements where great precision is necessary.”

The paper ends with a reassessment of Lambton’s values for the ellipticity of the earth**, correcting both the Indian and Engllsh measurements in terms of the new standard.

13. An account of the remeasurement of the cube, cylinder, and sphere, used by the late Sir George Shuckburgh Evelyn in his enquiries respecting a standard of weights and measures. (1 821)

In the event of the destruction of the standard of length, it could - it was believed at this time - be reconstructed by reference to Kater’s value for the length of the seconds pendulum. Having thus defined a length, it was possible to define a volume and the mass of distilled water occupy- ing this volume at a given temperature would constitute a reconstructed standard of mass. It was desirable, therefore, that the anticipated Act of Parliament should state the mass of a cubic inch of distilled water. Experiments towards determining this had been performed by Sir George Shuckburgh” by weighing accurately-made brass figures in air and in water. Kater accepts the results of the weighings but proceeds to check the linear dimensions of the solids, obtaining a final result which differs slightly from that of Sir George Shuckburgh. Observational results are given but for details of the calculation we are referred to the appendix of the third report of the Commission.

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14. Third Report of the Commissioners appointed to consider the sub-

This is given in Catalogue of Scientific Papers in the list of Kater’s papers but it is, in fact, signed by the five Commissioners; George Clerk, Davis Gilbert, W. H. Wollaston, Thomas Young, and Henry Kater.

An introductory paragraph notes that the Commissioners have now completed their examination of the standards of weights and measures; their results concerning the standard of length are contained in previous reports and the results concerning the standard of weight (i.e. mass) are given in an appendix. The recommendations follow. Briefly, these are that Bird‘s standard yard of 1760 and Harris’s Troy pound of 1758 are to be the legal standards, replaceable with reference to Kater’s values for the length of the seconds pendulum and the mass of a cubic inch of distilled water. (Both these standards had been constructed with the intention of making them the legal standards, but it was not until 1824 that this was achieved.) The gallon is to be the same for ale and corn, and is defined so that a gallon of “common water” weighs 10 Avoir- dupois pounds “in ordinary circumstances”.

The desirability of legal enforcement and publicity is stressed and the further services of the Commissioners are offered, if required.

All of the recommendations were made law in the Act (5th. Geo N. c. 74.) of 1824. At this, Parliament also requested the construction of new copies of the standards and these were provided by Kater.

ject of weights and measures. (1 82 1)

15. On the best kind of steel and form for a compass needle. (1821)

This paper was read as the Royal Society’s Bakerian Lecture for 182 1. It begins:

“On the return of the first expedition which sailed for the discovery of a north-west passage, it appeared that from the near approach to the magnetic pole, and the consequent diminution of the directive force, the compasses on board had become nearly useless. Some of the azimuth compasses employed on that occasion were of my own invention; I was therefore anxious that the next expedition. . . should be furnished with instruments of this description, combining as much power and sensibility as possible.”

After these opening words Kater describes experiments to find “the kind of steel, and form of needle best calculated to receive the greatest


directive energy with the least weight.” The “directive energy” og “directive force” is the couple exerted on the needle by the earth’s magnetic field and is measured by means of a Coulomb torsion balance.

In the complete absence of any theory it is interesting to read of the various tests and factors which Kater thought to include. Previous work by Biot and Coulomb is mentioned but no references are given. Several results of their investigations, though sometimes doubtful, are confirmed by Kater without thorough testing. In the main, however, the stated in- ferences from Katers’ results can be said to give a resonable practical guide for the manufacture of compass needles but the contribution to scientific theory is small. The results of Kater’s investigations were used in the construction of new compasses for later expeditions.

16. Notice respecting a volcanic appearance in the moon. (1821) This paper bears the date 8 February 1821 and was read before the

Royal Society on the same day. It records recent observations by Kater and some friends on an almost new moon. A bright spot was observed on the otherwise dark surface. This spot, of variable brightness, was situated in the region called Aristarchus and is undoubtedly the same as that described in Phil. Trans. 1787 by Sir W. Herschel, who attributed the luminosity to volcanic activity. An early alternative explanation was that sunlight reflected from the earth was picked up by Aristarchus, the brightest region of the moon’s visible surface. A more recent theory is that protons discharged from the sun cause luminescence in localised regions of the moon’s surface, notably around Aristarchus*g.

17. On the construction of a balance. (1 822) This is a very brief note which may best be presented by quoting the

opening lines. “I observe in the last number of the Quarterly Journal.. . the de-

scription of a balance from a drawing of Mr. Children. I should not have troubled you merely to claim this as my own arrangement, but to notice an error in the description where the beam is said to be “of platinum”; it should have been “of bell metal” which combines the essential deside- ratum lightness with the degree of strength.

This beam had its origin in a wish to render the hydrostatic balance less expensive without diminishing its accuracy and sensibility, and it has in every respect answered my expectations.”

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The balance referred to is described in Quarterly Journal 2 (1821) 280, with a note that it is available commercially. In his chapter on balances and pendulums in A Treatise on Mechanics (1830) Kater describes this design again and adds that it was used “in adjusting the national standard pound.

18. An account of experiments made with an invariable pendulum at New South Wales by Major-General Sir Thomas Brisbane. (1 823)

In the years following Kater’s pendulum experiments many similar experiments were performed in different parts of the world by British expeditions. The type of pendulum used was that which Kater had designed for observations at the principal stations of the Trigonometrical Survey, as reported in 18 19. The training of observers and the preservation of the pendulums was the duty of the Board of Longitude, of which Kater was one of the resident committee from the Board’s reconstitution in 18 18 to its dissolution in 1828.

This paper is one of the many reports of such observations. The cal- culations from observations made by Sir Thomas, Rumker, and Dunlop have been performed by Kater and are given along with a brief record of the experiments in London (at Browne’s house, as usual) and at Sir Thomas’s observatory, Panamatta. Values of the ellipticity of the earth are given for two series of experiments. The paper is dated London, June 1823 and was communicated as a letter from Kater, being read on 19 June. A short postscript corrects an error in calculation in the pendulum paper of 18 19.

The experiments were also recorded by Riimker in Astronomische Nachrichtenso.

19. The description of a floating collimator. (1825) and

20. A description of a vertical floating collimator; and an account of its application to astronomical observations with a circle and with a zenith telescope. (1 828)

Kater’s intention in these two papers is to develop a convenient and accurate means of determining the vertical or horizontal position for a meridian circle or similar instrument. He lists the three ways used to

The Scientific Publications of Henry Kater 1 67

find the altitude of a star, corrected for error of scale-zero. Two of these, using the plumbline or level, require the instrument to be turned half round in azimuth. The third, viewing the star directly and by reflection in mercury, does not impose the same strain on the instrument but nevertheless the two observations cannot be made simultaneously. In the first paper, read 13 January 1825, Kater proposes a “horizontal floating collimator”. The idea is inspired by remarks by BesseP’, dated July 1824. The relevant passage is quoted in translation.

The collimator is to be mounted horizontally on a stand which floats in mercury. The line of collimation thus defines a constant, almost horizontal, direction in space. This constancy has been tested extensively during December 1824. The line of collimation of the telescope is aligned with the constant direction, with the collimator first north, then south of the instrument. This is achieved by illuminating the cross-wires of the collimator; the parallel beam of light produced by the collimator, on passing through the telescope, gives an image of the cross-wires at the cross-wires of the telescope. Half the difference of the readings on the scale for the two positions gives the zero-error of the scale. Having determined this before observing begins, the altitude of a star can be measured without disturbing the telescope during the observation.

The possiblewe of a vertical form is mentioned in the first paper and taken up in the second, where its construction is described in detail. Here the collimator floats in a near-vertical position, either above or below the instrument. The exact vertical is also found by taking two readings but it is now only necessary to turn the float half round in azimuth. Kater ends with the words:

“If I have succeded in the object of this paper, I shall have demon- strated that the vertical floating collimator is an instrument capable of determining the zenith point with a precision hitherto unknown; that by its aid a meridional observation of an altitude or of a zenith distance may be completed, not only the same evening, but within the space of a very few minutes, and that too, without the necessity of turning the circle in azimuth. These are advantages which no other method of observing affords. . .”

From contemporary literature it appears that Kater’s collimators were widely known and welcomed, although their application seems not to have been widespread. The invention gained for him the Royal Astrono- mical Society’s Gold Medal for 1 83232.

168 Gordon Jones

The simplification of Kater’s method, by replacing the vertical floating collimator with a horizontal reflecting surface so that the telescope cross- wire coincides with its own image seems to be due to Bohnenberger. In an article dated 8 December 182533 he describes how a liquid surface alone can supplant Kater’s instrument, of which he had read in Annuls of Philosophy for February 1825 (page 143). Bohnenberger’s article also discusses the origin of the basic idea of the collimator.

21. Observations on Pallus. (1 826)

In a communication dated 30 April 1825 Kater notes that he has found the position of Pallas not to be that indicated by calculation. He gives observations made on Pallas as a result of this discovery, briefly describing his instruments and method.

22. An account of the construction and adjustment of the new stund- ards of weights and measures of the United Kingdom of Great Bri- tain and Ireland. (1 826)

Besides details of the secondary standards constructed under Kater’s direction, this paper contains references to his pendulum experiments of 1818-19. The paper opens with a discussion of the accuracy of their results which, Kater claims, is well supported by Biot’s experiments recorded in Base du Systtme Me‘ t r iq~e~~ , and not diminished by doubts about his method of observing coincidences. The paper also carries a postscript dated London, 31 December 1825. This records his receipt of Bohnenberger’s AstronomieI6 to which Schumacher has called his attention. Kater quotes a translation of the passage in which Bohnenberger has proposed the use of a reversible pendulum. He concludes:

“Although it does not appear that this idea was ever put in practice, it is evident. . . that the first proposal to determine the length of the seconds pendulum by means of the convertible pendulum belongs to Professor Bohnenberger, and I take the earliest opportunity of acknowl- edging his claims, in order that the credit of the first suggestion may rest where it is so justly due.”

The major portion of the paper describes the preparation of a complete series of secondary standards of weights and measures, beginning with a summary and brief explanation of the recommendations of the


Weights and Measures Commission. In compliance with a request from the Treasury, Kater has agreed “to superintend the construction, and to adjust the standards to be deposited at the Exchequer, Guildhall, Dub- lin and Edinburgh.”

Bate and his engineer Keir are mentioned as performing the main work on the standards of mass and volume. Robinson produced the various balances required and Dolland is responsible for the standards of linear measure. These are of two types. The first is to be used to regulate commercial standards; steel projections on a brass bar mark the length of the Imperial Standard Yard. The second type is intended as a replica of the Imperial Standard; the distance is marked by dots on gold studs, and so that the distance might be transferred exactly, the dots are made adjustable. This is accomplished by making the studs capable of rotation and marking the dots off-centre. With this fine adjustment Kater hopes to produce exact copies of the Imperial Standard Yard but instead he detects a source of considerable error. An almost imperceptible bending of the bar can cause one surface of the bar to be compressed and the opposite one to be extended to such an extent as to make non- sense of the measured length. The difficulty is overcome by cutting away part of the thickness of the bar at each end so that the gold studs now lie on a surface mid-way between that extended and that compressed.

A list is included, giving all the standards and the places where they are to be deposited. Npw, specimens of many of these standards can be seen in the Metrology Collection of the Science Museum, London.

The work of preparing the standards was finished in time for the paper to bear the date November 1825, and in the final paragraph Kater sums up the position in the subject of weights and measures as he sees it. The impression is of great satisfaction. But Kater was not to know that his pendulum experiments would be discredited in the following year” and that fire in the House of Commons would destroy the Im- perial Standards in 1834.

23. An account of trigonometrical operations in the years 1821, 1822 and 1823 for determining the difference of longitude between the Royal Observatories of Paris and Greenwich. ( I 828)

After completing his work on weights and measures in 1821, Kater was appointed with C01by~~ to cooperate in a remeasurement of the dif-

13 CENTAURUS. VOL. X I

170 Gordon Jones

ference of longitude between Paris and G r e e n ~ i c h ~ ~ . Their counterparts from the French side were Arago2I and Matthieu, and the work took place in the years between the final report on weights and measures and its becoming law in 1824, at which Kater was appointed to supervise the construction of new standards. The paper was read on 31 January and 7 February 1828 and the original results deposited with the Royal Society.

The report refers briefly to the previous measurement and then tells how the observers carried out their work in this case, connecting the stations on each side of the Channel by means of powerful lights, designed by Fresne13’, and using Ramsden’s 36 inch theodolite, The method of computing the triangles is that due to Legendre and the method of determining the latitude and longitude is due to 0riar1.i~~. After the main results comes an appendix giving a discussion of the tests made on the instruments, the precautions taken and the possible errors.

24. On a luminous zone observed in the heavens on the 29th of Sep- tember 1828.

The aurora, seen at Stevenage, was described briefly by Kater in The Times of 4 October 1828. This is a description of the same event with a view to the better preservation of the record. The description was reprinted in German in Annalen der P h y ~ i k ~ ~ and a description appears in French in Astronomische Na~hrichten~~ over the name of Moll, who was with Kater at the time of observation. It figures again in Arago’s collection of many such obser~ations~~.

25. On the error in standards of linear measure, arising from the thickness of the bar on which they are traced. (1 830)

Following his discovery of the errors which can occur in line-standards as a result of flexure of the bar on which the lines are marked (Phil. Trans. 1826) Kater here records a series of experimznts to investigate the matter further. Fine wire of known diameter is placed under the centre or under the ends of various standards and the variation in the distance between the defining lines is noticed. The conclusions from his previous experiments are reinforced and a quantitative assessment obtained. Kater tackles the problem of finding a plane surface by testing with a streched piano wire and decides that the best surface is a marble slab.


His results show that all previous comparisons of line-standards must be doubted and that only standards which have their lines marked on a neutral plane can be trusted not to vary in length from this cause. This principle was incorporated in the construction of the present Imperial Standard Yard in 1845. Kater points out though that this method cannot be applied to standards requiring subdivisions. The standards constructed under Kater’s direction for the Governments of Russia (1832) and Hanover (1828) are thus of a different pattern. The inch divisions are carried on an extremely thin plate which lies in a groove in a larger bar and is fixed to the larger bar by a single screw at its centre.

The paper was read 17 June 1830.

26. An account of the construction and verification of a copy of the Imperial Standard Yard made for the Royal Society. (1831)

This is a very short paper, read on 19 May 183 1. The standard described was constructed by Dolland and follows the pattern given in PhilosophicaE Transactions for 1830, for standards bearing subdivisions. The supporting bar and the scale of divisions are both of brass, the latter being 0,07 inches thick. The scale is divided into inches by fine dots upon gold discs let into the brass and carxies an extra inch which is subdivided into tenths. The Imperial Standard was laid on the same slab of marble as had been thoroughly tested previously and proved sufficiently plane. The optical comparison was performed with the same apparatus as used in most of Kater’s work, being derived from that of Sir George Shuckburgh and described in Philosophical Transactions for 1821.

Sheepshanks later referred to these comparisons of the Imperial Stand- ard and the scale of the Royal Society as Kater’s “most complete work in linear measurement”“.

c

27. An account of the construction and verification of certain standards of linear measure for the Russian Government. (1832)

The only copy of this tract known to me is that held in the library of the Royal Society, to whom it was presented by Kater himself. I t describes the preparation of:

’

A Yard, equal to the English Imperial Standard Yard, A Foot, equal to one English foot, An Arshine, equal to twenty-eight English inches,

13.

172 Gordon Jones

A Saghe, equai to seven English feet, and A measure of Two Sagknes, equal to fourteen Enghsh feet. These were constructed by Dolland according to Kater’s pattern for

standards bearing subdivisions, these divisions being denoted by “well- defined circular dots, made upon small discs of gold let into the iron plate.” The use of iron, specified by the Russian Government, produced several difficulties. To protect the standards against rust they were warm ed and rubbed in oil. Moreover, Kater adds:

“I thought it advisable to adopt the electrogalvanic principle employed by the late Sir Humphrey Davy, for protecting the copper sheeting of ships, and I caused the cases containing the standards to be lined with zinc - whether this will prove efficient or not, it is for time to determine.”

Ill-health interrupted the work of comparison and the standards (except for the sagknes) were removed from the city to Tunbridge Wells in early April 1832 so that Kater could continue his work there. The verification of the sagbes was achieved in May, completing the series of final values given on page 27. The account is dated London, May 1832.

The original measurements for the comparisons are included in a manuscript notebook of Kater’s in the library of the Royal Society. This contains notes on a wide range of topics - mostly scientific. It is noted by biographers that in recognition of his services Kater received the Or- der of St. Anne and a diamond snuff-box.

28. A Treatise on Mechanics. (1830)

The Cabinet Cyclopcedia, conducted by Dionysius Lardner, contains 133 volumes, “written in a popular and generally intelligible style.” This is the fifth volume to be published and like maqy of the series it was reprinted in America and translated into French, German and 1talia.11~~. Whether this popularity was due to Kater’s well-known nams in the field or to Lardner’s business sense and contacts is a matter of opinion. Kater’s contribution was, however, quite a small part of the whole; in fact, the last of 21 chapters. Nevertheless, he speaks with authority on the subject of Balances and Pendulums.

The chapter occupies pages 278-340 of the book and begins with a discussion of the beam balance and its sensitivety. A description is given of a balance by Troughton which includes the many important fea- tures of a well-designed balance, and of the balance mentioned previously (page 165). This was the type of balance constructed by Robinson


and used by Kater in preparing five copies of the Imperial Stand- ard (Troy) Pound (page 169).

Two other balances are described in the section. The first, “perhaps the most sensible that has yet been made, constructed for verifying the national standard bushel”, is designed to weigh large weights. The description is taken directly from Philosophical Transactions of 1826. The second, “a very sensible balance used by the late Dr. Black, is for weighing very small weights and the description is taken from Annals of Philo- sophy for 1825. Practical hints are given for the care and preparation of weights and for the use of the balance before going on to discuss the various forms of commercial weighing machine. Several kinds of steel- yard and spring instruments are described and shown in diagrams, and their respective virtues considered.

On page 307 Kater ends his comments on instruments for the measurement of mass and begins those on instruments for the measurement of time. However, space does not allow a full discussion and the treatment is thus limited to the pendulum. Since a general introduction appears in the earlier chapters Kater concentrates on compensation pendulums. A brief historical introduction is followed by practical details for the construction and calculation involved in producing a pendulum, compensated for changes of temperature, from two solids of differing expansion coefficients. Quite a number of examples of this type are given, including Kater’s own compensation pendulum (page 153) which has now been tested and found to be very satisfactory. It is followed by Reid‘s compensation pendulum which resembles Kater’s greatly, except that the rod is of steel instead of wood and there is no form of adjustment. The resemblance was pointed out in Nicholson’s Journal in 18 12 by “A Cor- respondent”“‘.

The calculation for the mercurial pendulum is considered and examples of this type of compensation follow. The chapter is concluded with brief comments on the effect of an atmosphere in reducing the amplitude of vibration and in reducing the effect of gravity by buoyancy; and with notes on the practical care and adjustment of pendulum clocks.

29. On an appearance of divisions in the exterior ring of Saturn. (I83I)

In the chapter Elusive subdivisions in the rings of his book, The Plan- et Saturn, Alexander refers to this paper as “an important original source”4s.

Gordon Jones 174

Since Saturn provides a good test for the quality of a telescope, Kater often had cause to observe the satellites and ring system. On one occasion, 17 December 1825, he was struck by the appearance of the southern face.

‘‘. . . I fancied that I saw the outer ring separated by numerous dark divisions extremely close, one stronger than the rest dividing the ring about equally.”

Kater’s diagram shows three divisions in the outer ring. Two friends, requested to view the planet on the same occasion, confirm that some division is visible but observed details differ. The reading of the paper was delayed until May 1830 in the hope that further observations might give more evidence but bad health and poor weather conditions prevented this. Some observations were possible but the markings were not seen. On the remarkably fine evening of 22 January 1828 Kater wrote “. . . no divisions seen in the outer ring. I am, therefore, the more persuaded that they are not permanent.”

Other observers are mentioned as having seen the divisions but nothing had been published on the topic4s. It was not until 1837 that Encke, using a more powerful telescope, observed a dark division in the northern face of the outer ring and measured its position. In his paper in Astro- nomische Nachrichte4’ he is quick to point out that Kater has used the words, “I fancied, and since then the markings on both faces have been known as Encke’s division, assuming that they are part of the same gap.

The paper appears again in note form in the Royal Astronomical So- ciety’s Monthly Noticesa.

30. On a method of determining the longitude with considerable accuracy by means of lunar eclipses. (1 833)

This paper appears only in note form in the ROYG~ Astronomical So- ciety’s Monthly Notices for 12. April 1833 because the appropriate Memoir was taken up by the report of a scientific voyage which was conducted by Captain Foster to swing pendulums on the equator and in the southern hemisphere, and which led to his death. The paper describes a method of finding the longitude of a place by determining the exact time of the passage of the earth‘s shadow across the middle of the moon and then comparing this time with the time of the middle of the eclipse for the longitude of Greenwich.


The method proposed is not simply to note the time at the beginning and end of the eclipse but to measure the illuminated portion of the moon’s surface as a function of time. Specimen results are given from observations of the lunar eclipse of 2 August 1832.

Captain Beaufort has suggested that the method lends itself readily to use at sea with a sextant and Kater visualises an accuracy “much within one minute of the truth, which is far within the limits of the errors assigned by different writers to observations made in the usual manner.” The method is not new, however, since Kater refers to Lalande’s Astro- n o d e (1764) where the same idea is proposed, but this appears to be the first time it has been put into practice.

3 1. On the certainty and safety with which the operation of the extraction of a cataract from the human eye may be performed. With remarks by Captain Kater . . . on certain spots discoverable in the human eye. (1834)

This pamphlet, sold to raise funds for the Royal Westminster Opthal- mic Hospital, contains 47 pages. Kater’s remarks form the last three pages only and are printed directly as a letter from him to Guthrie, dated 15 April 1834, a time when Kater’s eyesight had become so poor as to prevent the continuance of his normal scientific activity.

The notes concern the “. . . mode. . . of detecting spots which may exist in the crystalline lens, or in the vitreous humour of the eye.” The spots are not to be confused with the particles of mucus on the cornea, for they are not visible under normal circumstances but ‘‘. . . may, however, prove a most serious evil to the scientific observer, as their shadow is perceptible on looking through a telescope of high power.” This, we may assume, is how Kater first became aware of them in 1825. The discovery was not unanticipated since Wollaston, at least, already knew of their existence and in consequence Kater had not previously published anything on the topic.

The detection of a spot may be achieved by holding a strongly diverg- ing lens close to the eye and viewing a distant flame. The presence of the spot is shown by its shadow cast on the retina; the shadow should of course remain stationary when the lens is rotated. Using coverging lenses of different powers in a similar way, the approximate position of the spot can also be found.

Gordon Jones 176

Related Materid

In addition to the publications already mentioned, two others are of interest. Both are referred to in Catalogue of Scientific Papers. The first reference is:

Kater, - - - . Sur la grosseur des molicules du sang. Annal. de Chimie, X, 18 19, pp. 204-207. This is a note derived from Sir Everard Home’s Croonian Lecture of

18 1 749. It contains principally the method used by Kater to measure the diameter of blood corpuscules. By simultaneously viewing a fine scale through a microscope with one eye, and a ruler divided into inches and tenths with the other eye unaided, a value is obtained for the magnifica- tion of the microscope. A specimen of blood, when substituted for the fine scale can thus be examined superposed on the scale of the ruler and the diameter of the corpuscules is easily obtained. The value (about one five-thousandth of an inch) compares well with previous measurements by Wollaston and Young.

The contribution is unsigned but we can assume that it was written by one of the editors, Arago and Gay-Lussac.

The second reference is: Kater, Edward. Description of an escapement for an astronomical clock, invented by the late Capt. Henry Kater. Phil. Trans. 1840, pp. 335-340. Edward Kater was Henry Kater’s son but as yet this is the only men-

tion of him I have come across. The escapement he describes in this paper was the result of many years consideration by his father, and is taken from notes left after his death, many of them dictated to Edward who is thus able to describe Kater’s escapement “nearly in his own words”.

Kater’s objections to the types of escapement in use are given. Gra- ham’s dead-beat escapement requires that the impulse given to the pendulum come directly from the teeth of the scape-wheel. Mudge’s gravity escapement requires the pendulum to unlock the scape wheel, meeting a resistance in so doing which is dependent on the driving force trans- mitted through the train. To have an impulse, the constancy of which is dependent on the constancy of driving force is, in Kater’s view, a “fatal defect”. In addition, Mudge’s escapement is liable to trip if the weight is increased.


In Kater’s construction, then, “the great object was to discover a mode of communicating equal impulses to the pendulum through some principle perfect in itself, and not dependent for its success on superior execution”. The remontoire escapements available do not meet this condition since they too allow the pendulum to unlock a detent from the scape- wheel. To remove dependence on good workmanship the form of Kater’s escapement is described in which “the pendulum of the escapement. . . merely raises a weight and is impelled by that weight through an increased space in its descent; it neither unlocks a detent, nor has anything to do with the train; and as the weight raised and the spaces described are constant quantities, this escapement is in the strict meaning of the term one of equal impulse.’’

To achieve this the pallets and detents are separated. The pallets are connected to gravity arms as in Mudge’s escapement and are partly raised by the scape-wheel previous to their further raising by the pendulum and subsequent dropping through a well-defined distance, during which the impulse is given to the pendulum. The detents are placed on an anchor whose function is to regulate the scape-wheel. The unlocking of a detent from the scape-wheel is caused by the impact on the opposite arm of the anchor from the falling gravity arm.

In such a refined system one might expect easy derangement and trip- ping but we read

“To calculate with accuracy the time the arm is detained is perhaps impossible, but a sufficient approximation to this may, and has been made, to demonstrate that it cannot overtake the pendulum during the unlocking of the scape wheel, which is all that is necessary.”

This undoubtedly refers to Young’s “Demonstration that the arm of Captain Kater’s escapement cannot overtake the pendulum” which appears on page 31 of Kater’s manuscript notebook in the Royal Society library.

The construction, adjustment and action of the escapement are described in detail. It has been used with a mercurial pendulum but has not been tested exhaustively. Later use of the escapement appears to have been neghgible but a search of specialized literature may reveal some- thing?

The paper was received 26 March, and read 30 April 1840.

178 Gordon Jones

Published Letters.

Four letters written by Kater have come to my notice. Two of these are directly connected with his scientific work; the other two, written to orsted, are of a more personal nature.

In Astronomische NachrichterP we find a letter which is dated 7 June 1825 and which is a reply to Schumacher, the editor, who has pointed out Bohnenberger’s proposals for a reversible pendulum in 18 1 116. Kater expresses surprise that the news of it has never reached England or France. He promises to send Schumacher a floating collimator and the paper (Phil. Tram. 1825) describing its uses2.

The construction of new standards, and in particular the new definition of the gallon, caused great interest in commercial circles during the years around 1824. Comment appeared in trade journals and in one, the Mechanics Magazine, a letter from Kater to the Commissioners of Weights and Measures is reprinted in fulls3. The letter is dated 12 Janu- ary 1825 and gives a report on the progress of the construction of the new standards and explains the delay in producing the bushel measures4.

The two letters to grsted are included in the collection of his correspondence published by Hardings. The introductory paragraphs read:

“The first meeting of the English physicist Henry Kater and H. C. grsted took place in England in the summer of 1823. Kater determined the intensity of terrestrial magnetism in London with Hansteen’s apparatus, which arsted brought with him on the journey. These determina- tions were used by Hansteen in an article on the magnetic intensity in northern Europes6.

The following letters give an idea of Kater’s sickly condition of which Berzelius had spoken in rather coarse terms in his diary”s7.

This seem rather unfair to Benelius, who was merely relating a story heard when he dined with the Royal Society Dining Club on 6 August 1818. The story is used as an example of the conversation, which “in such learned company as this, could of course be nothing but highly edifymg.” The irony of his words becomes all too apparent when we read of a trick played on Kater by one of his friends, taking advantage of his tendency to hypochondria.

The first letter is dated 12 August 1823. It contains Kater’s apologies for being unable, through reasons of ill-health, to see Ibrsted again before he left London. The indisposition has also prevented any repetition of the magnetic experiments. Greetings sent include those of Mrs. Kater.

The Scientific Publications o f Henry Kater 179

The second, dated 17 February 1826, records Kater’s thanks for the Diploma of the Royal Society of Sciences of Copenhagen and an apology for the lateness (about a fortnight) of acknowledgement - again the result of poor health. Special mention is made of a paper read at the Royal Society which has impressed Kate?* and the letter ends with greetings, this time including both Kater’s wife and daughter (who was then 15 years old and was to die the following year). A postscript indicates the inclusion of two copies of Kater’s paper from Phil. Trans. 1826 on the new standards of weights and measures. One of these is for the Royal Society of Copenhagen and the other for Qrsted personally.

Conclusion

In the preceding pages I have tried, through collecting together and out- lining the content of Kater’s published works, to give an indication of his activities and contribution to scientific development. The list of publications is probably very nearly complete and may be taken as a basis for some evaluation of Kater the scientist and, to some extent, of Kater the man.

The publications seem to separate themselves into three overlapping groups. Many of the papers deal with mechanical inventions, usually di- rected towards the solution of some definite problem. Others are reports of official undertakings such as the pendulum experiments, the construction of standards or the trigonometrical surveying. The third group con- sists mainly of miscellaneous observations on astronomical phenomena and scientific instruments. This latter group might be regarded as a natural supplement to the other two, serving to emphasise Kater’s interest in and capacity for nicety of observation. It is the smallest group and the most varied in its content; but even so, the variation is confined to the rather narrow and closely-knit field in which Kater restricted himself. The major content of his published work is thus divided roughly equally between reports written after carrying out work of an official nature and papers demonstrating his capacity for invention.

That Kater possessed this capacity is evident. Given a practical difficulty he could very often develop the mechanical means of overcoming it. His ideas were not always original but since he usually quotes his sources of inspiration we can assume that most of them were arrived at independently. A major advantage seems to have been his ability to put ideas into practice; the outstanding example of this is of course the re-

180 Gordon Jotics

versible pendulum. The design and testing of his productions were, however, largely dependent on practical methods. The development would be carried patiently and throughly to the limit of Kater’s practical ability but the theoretical analysis of a problem seems to have been beyond him. The mathematics which appears in his papers is almost entirely calculation from formulae derived by others and his notebook in the Royal So- ciety library shows that he was in the habit of copying out proofs and methods of calculation.

The other aspect of Kater’s work, as an energetic member of the Pen- dulum Committee and the Board of Longitude, shows us a man experi- enced and skilful in the use of instruments; someone who could, moreover, be trusted to carry through an undertaking which required great attention and considerable public expense.

If we examine the part played by Kater in the scientific development of his day we see from his publications that he produced nothing of earth-shattering importance. Indeed, it is unfair to judge him in the same light as those few whose work has transformed the scientific scene. Kater was a moderate man of modest achievement, and would probably be the last person to claim greatness for himself. His lot was, for the most part, to perform the necessary tasks for which his greater contemporaries had no time.

Kater was obviously sufficiently satisfied with this lot to continue the work. It was, of course, no mean feat to become the acknowledged ex- pert that he was, in the design and handling of instruments, at a time when London was the centre of a scientific-instrument trade which was renowned the world over. This was, after all, the ase of the mechanically- minded man. While the strongest tradition of theoretical science had been established in France and Germany, developments in Britain - unimped- ed by the presence of war - had been towards mechanisation and the Industrial Revolution. Trade was flourishing and the existence in Lon- don of some of the world‘s best craftmen was evidence of the prosperity, without which these craftsmen would have lost the patronage of their wealthy clients. That some of this prosperity came Kater’s way is fairly certain, but it would be ridiculous to suggest that Kater’s intention in his scientific work was merely to boost his standard of living. His activities involved a great deal of honest endeavour towards the improvement of scientific accuracy. What he gained from this, sufficient to overcome the distractions of indifferent health, would be the satisfaction of seeing


his instruments put to immediate and often extensive use, and the honour of giving a worthwhile service to the Governments whose commis- sions he executed. Of the instruments Kater designed, the invariable pendulum and azi-

muth compass were most successful, becoming part of the standard equipment in scientific expeditions of the time. However, during a period of such rapid development they were soon to be replaced, having served their purpose of providing stepping-stones on the long path of development.

The pendulum has of course changed its form least over the years and its cousin, the reversible pendulum, is still associated with Kater’s name. To him we owe the demonstration of the great precision.attainab1e in the determination of the absolute value of the acceleration due to gravity (g) with the reversible pendulum. Although other methods are available, and although the small but uncertain errors from the knife-edges are en- evitable, this method remains one of the most important. The measurement of the relative vaiue of g can be more accurate and offers a wide range of methods but here Kater’s influence was of lesser importance. He did, however, point out the accuracy with which the local variation in the geologicd structure could be determined using a pendulum. He never went so far as to use the pendulum as an instrument for geophysical prospecting but it would be interesting to see what influence, if any, Kater’s remarks had on the introduction of this method by prospectors. Kater’s compass appears to have been quite widely used but it is rarely mentioned in historical literature, which, if it mentions the simultaneous sighting and reading of a bearing, usually quotes the prismatic method (Schmalcalder, 1812) in preference to Kater’s method using an inclined mirror and lens system. A specimen of Kater’s type of compass is to be seen in the Conservatoire National des Arts et Mttiers, Paris.

The other instruments described in Kater’s publications received much more limited employment. The apparatus for dividing astronomical circles and the floating collimators were tested by contemporary workers and found satisfactory, but were again only tcmporary. Even While Kater was carrying out the important work of showing that the methods were possible in practice, variations and improvements of them were proposed by others in a constant flow of new ideas. The work of constructing standards demanded an ever-improving range of apparatus, which Kater often designed himself. This was apparatus which had to

182 Gordon Jones

work satisfactorily; some of it (balances, for example) is described in the literature, but its wider application is not apparent. Neither is that of Kater’s early instruments, the hygrometer and compensation pendulum, nor that of his last, the escapement.

Kater’s reputation as a man of science depends largely on his work with standards of weights and measures. Today, few remember his name except in connection with the reversible pendulum. In his own lifetime, it was the experiments with the seconds pendulum which made his name in scientific circles, and his construction of standards which kept him in the public eye. The period of Kater’s activity in this field can be taken as about 15 years (1 8 17-1 832). What did he achieve in this time?

In such a period of almost continual work with accurate measurement Kater contributed much to the practical knowledge of construction and use of materials; but more important was his attention to accuracy. His early work, in connection with the Weights and Measures Act of 1824, showed that the measurement of the length of the seconds pendulum could be made accurately using a compound pendulum. The length obtained from previous methods using simple pendulums had a much greater degree of uncertainty and this overshadowed the lack of accuracy in the corrections used. Although Kater’s value was wrong, it gave the scientific world a new start in the discussion of the corrections which were required. That Bessel’s later criticism of Kater‘s result was based on experiments with a combination of simple pendulums does not detract from the importance of Kater’s method.

It was in the early work, too, that Kater’s examination of the multi- plicity of standards once again indicated the need for reform. This had of course been recognised for many years and it was perhaps more to the credit of the Members of Parliament involved that the Weights and Measures Act became a reality and provoked widespread comment and publicity. But Kater’s contribution in this and later work was to push the accuracy of measurement as far as he was able, thus enabling unknown sources of error to be singled out and corrected. During this pen- od we find a much greater awareness of the effects of, €or example, temperature, illumination, methods of marking divisions, and flexure of the bar. It was in the latter that Kater made his most conspicuous contribution, but was it his greatest? In my opinion his greatest contribution was the rather negative one that, in spite of his practical talent, he was unable to solve all the problems which beset a constructor of standards.


By increasing the quality of comparison and construction he demonstrat- ed just how difficult the preparation of accurate standards really was and indicated that the subject was considerably more complicated than had been suspected. It is doubtful whether Kater fully realised this, but looking back over his efforts helped convince later constructors that no satisfactory result could be expected without considerable preparatory research. In consequence, the standards which, in 1855, replaced those destroyed in 1834 were the results of extensive trials and enormous expense.

Thus, apart from a few concrete examples, Kater’s contribution to scientific progress appears to have been in the active support of the scientific life. The part he played was certainly a useful and, in some ways, an essential one. Science would make very slow progress indeed if it did not have the help of an army of such dedicated workers, each contribut- ing where he is best able. That Kater’s contribution was largely in his continuous application to the elimination of practical difficulties would, I think, make him more deserving of the title of “mechanician” than of “scientist”, but his work and qualification for a place in history remain unaltered.

In spite of his playing only a minor role in the sphere of scientific achievement, Kater had a name which was well-known throughout the scientific world. This resulted from his reputation as one of the foremost authorities on scientific instruments, from his close association with the Royal Society, and from the work he did with the seconds pendulum and standards. In consequence, he counted many of the great scientists of the time among his friends and he must be regarded as a suitable figure for study in forming a complete picture of the scientific milieu of the early 19th. century. In this paper I have tried to provide a collection of Kater’s published work and to place him in a historical context. This will, I hope, be able to provide a starting-point for any further study which may be undertaken into his unpublished papers and correspondence. If such material still exists it would certainly reveal further information of Ka- ter’s life, times and contemporaries.

Gordon Jones 184

LIST OF PUBLICATIONS

1. Description of a very sensible hygrometer. Asiatic Researches 9 (1807) 24-31.

2. Description of an improved hygrometer. Asiatic Researches 9 (1807) 394-397.

3. Description of a new compensation pendulum. Nicholson’s Journal 23 (1 808) 214-220.

4. On the light of the Cassegrainian telescope, compared with that of the Gregorian. Philosophical Transactions (1 81 3) 206-2 12.

5. Further experiments on the light of the Cassegrainian teleszope, compared with that of the Gregorian. Philosophical Transactions (1 814) 23 1-247.

6. Upon the interruption which the situation of the maintaining weight produces in the rate of a clock, when near the pendulum. Nicholscn’s Journal 34 ( 1 8 13) 146-1 47.

7. An improved method of dividing astronomical circ!es and other instruments. Philosophical Transactions (1814) 419-435.

8. An account of experiments for determining the length of the pendulum vibrating seconds in the latitude of London. Philosophical Transactions (1 8 18) 33-102.

standard. Philosophical Transactions (1 8 18) 103-1 09.

10. An account of experiments for determining the variation in the length of the pendulum vibrating seconds, at the principal stations of the Trigonome- trical Survey of Great Britain. Philosophical Transactions (1 8 19) 337-508.

11. Instructions for the adjustments and use of the instruments intended for the Northern expeditions. (By H. K. and others) London, 1 8 18.

measure. Philosophical Transactions (1 821) 75-94.

13. An account of the remeasurement of the cube, cylinder, and sphere, used by the late Sir George Shuckburgh Evelyn in his enquiries respecting a standard of weights and measures. Philosophical Transactions (1821) 3 16-326.

14. Third Report of the Commissioners appointed to consider the subject of weights and measures. Quarterly Journal of Science and the Arts 11 (1821) 378-380.

15. On the best kind of steel and form for a compass needle. Philosophical Transactions (1 821) 104-1 29.

16. Notice respecting a volcanic appearance in the meon. Philosophical Transactions (1 821) 130-1 32.

9. On the length of the French m&re estimated in parts of the English

12. An account of the comparison of various British standards of linear


17. On the construction of a balance. Quarterly Journal of Science and the Arts 12 (1822) 4 0 4 1 .

18. An account of experiments made with an invariable pendulum at New South Wales by Major-General Sir Thomas Brisbane. Philosophical Transactions (1 823) 308-325.

19. The description of a floating collimator. Philosophical Transactions (1 825) 147-178.

20. A description of a vertical floating collimator; and an account of its application to astronomical observations with a circle and with a zenith telescope. Philosophical Transactions (1 828) 257-289.

21. Observations on Pallas. Astronomische Nachrichten 4 (1 826) col. 1 13-1 16.

22. An account of the construction and adjustment of the new standards of weights and measures of the United Kingdom of Great Britain and Ireland. Philosophical Transactions (1826) pt. 2. 1-52.

23. An account of trigonometrical operations in the years 1821, 1822 and 1823 for determining the difference of longitude between the Royal Ob- servatories of Paris and Greenwich. Philosophical Transactions (1 828) 153-239.

24. On the luminous zone observed in the heavens on the 29th. of September 1828. Philosophical Magazine 4 (1828) 337.

25. On the error in standards of linear measure, arising from the thickness of the bar on which they are traced. Philosophical Transactions (1 830) 359-38 1.

26. An account of the construction and verification of a copy of the Imperial Standard Yard made for the Royal Society. Philosophical Transactions (183 1) 345-347.

linear measure for the Russian Government. London, 1832.

28. A Treatise on Mechanics. (Part of the Cabinet Cyclopzdia) (by D. Lardner and H. K) London, 1830.

29. On an appearance of divisions in the exterior ring of Saturn. Royal Astronomical Society Memoirs 4 (1831) 383-390.

30. On a method of determining the longitude with considerable accuracy by means of lunar eclipses. Royal Astronomical Society Monthly Notices 2 (1831-33) 178-180.

31. On the certainty and safety with which the operation of the extraction of a cataract from the human eye may be performed. With remarks by Captain Kater.. .on certain spots discoverable in the human eye - (by G.H. Guthrie) London, 1834.

27. An account of the construction and verification of certain standards of

14 CENTAURUS. VOL. XI

186 Gordon Jones

N O T E S A N D R E F E R E N C E S 1. The best biography of Kater is in Dictionary of National Biography. This

refers the reader to other biographical notes but these add little to this mainly accurate entry.

An engraving of Kater, taken from the portrait reproduced here between page 152-153, appears in the well-known group, Dktinguished Men of Science of Great Britain living in the years 1807-8. This was accompanied by a book of biographical notes compiled by W. Walker jun. (London, 1862)

The fullest obituary notice of Kater appears in Royal Astronomical Society’s Memoirs 9 (1 836) 290.

2. South, J. Charges against the President and Councils of the Royal Society. London, 1830. Babbage, C. The Decline of Science in England. London, 1830. Granville, A. B. Science without a Head. London, 1830.

3. The Royal Society’s Catalogue of Scientific Papers provides a list of Kater’s main papers.

4. Philosophical Magazine 27 (1809) 322. 5. Nicholson’s Journal 23 (1809) 207. 6. Ramsden, J. Philosophical Transactions (1779) 427. 7. Principia. Book 2, Sec. 6, General Scholium. 8. ibid., Book 2, Prop. 27, Cor. 2. 9. Baily, F. Philosophical Transactions (1832) 399.

10. Troughton, E. ibid., (1809) 105. 11. For a historical survey of the methods of dividing circles, and for that of

the Duc de Chaulnes in particular, see Daumas’ chapter on Precision Mechanics in Vol. 4 of A History of Technology (Oxford University Press, 1958)

12. Royal Astronomical Society’s Memoirs 9 (1836) 25. 13. The literature on pendulums is vast. However, two extremely useful biblio-

graphies are available. (a) The fifth volume of Great Trigonomezrical Survey of India (Calcutta,

1879) is devoted to the pendulum observations. Among the interesting appendices, the fifth and last is J. Herschel’s A bibliographical List of Works relating to Pendulum Operations in connection with the problem of the Figure of the Earth.

(b) The fourth volume of Collection de Mtmoires relatifs a la Physique (published by La Soci6tt6 Franpise de Physique, Paris, 1889) is entitled Mkmoires sur le pendule and contains, besides the bibliography, a historical survey by C. Wolf and reprints (in French) of important papers on the seconds pendulum, including Kater’s from 18 18.

14. The subject of weights and measures in Britain also has an extremely involved history. For a general treatment, see: Davison, C. St. C., B. Land- marks in the History of Weighing and Measuring. Transactionr of Newcomen Society 31 (1958) 131-152. Skinner, F. G. The English Yard and Pound


15. 16.

17. 18.

19.. 20.

21. 22.

23. 24. 25. 26. 27. 28.

29. 30. 31. 32.

33. 34. 35.

Weight. Bulletin of British Society for History of Science I (1952) 169. Chisholm, H. W. On the Science of Weighing and Measuring. London, (1877). (See also Nature 8 (1873) for the articles which form the basis for the book.) For the particular period of Kater’s activity the major references must be: Airy, G. B. Account of the construction of the new national standard of length and of its principal copies. Philosophical Transactions (1 857) 621. Miller, W. H. On the construction of the new Imperial Standard Pound . . . Philosophical Transactions (1856) 753. Huygens, C. Horologium oscillatorium. PdS, 1673. The two publications expressing the same idea were: Prony, G. de. Mkthode pour dkterminer la longueur du pendule simple qui bat les recondes. (1800). Bohnenberger, J. Astronornie. Tubingen, 18 1 1.

quotes extensively. Shuckburgh, Evelyn, G. A. W. Philosophical Transactions (I 798) 133. By Young, T. Philosophical Transactions (1819) 70, and Troughton, E. Edinburgh Philosophical Journal I (1819) 75. Bessel, F, W. Abhandlungen der Berliner Akad. (1826) 1. Mudge, W. Philosophical Transactions (1 803) 383.

Ordnance Trigonometrical Survey of Great Britain and Ireland. ( I 858)

4 of A History of Technology (Oxford University Press, 1958) See: Arago, F. Oeuvres Complstes I1 (Mthoires Scientifiques 2) 108. The Catalogue of Scientific Papers mentions particularly Edinburgh Philo- sophical Journal 2 (1820) 319, which contains an extract from the second paper. The results are given by Sabine, E. Philosophical Transactions (1821) 163. Sabine, E. ibid, (1819) 140. Sabine, E. ibid, (1819) 112. Roy, W. ibid, (1785) 385. Baily, F. Royal Astronomical Society’s Memoirs 9 (1836) 53 and 81. Lambton, W. Philosophical Transactions (1 8 18) 486. For Lambton’s comments on Kater’s paper see Philosophical Transactions (1 823) 27. Kopal, Z. and Rackham, T. W. Nature 201 (1964) 239. Riimker, K. L. C. Astronomische Nachrichten 3 (1825) col. 261. Bessel, F. W. Astronomische Nachrichten 3 (1825) col. 209. The Presidential Address (by South) on the occasion of presentation is printed in the Society’s Memoirs 5 (1831-32) 394 and Monthly Notices 2

Bohnenberger, J. Astronomische Nachrichten 4 (1 826) col. 327. Biot, J. B. and Arago, F. Base du syst2me Mbtrique, Vo2.4, Paris, 1821. Further information on these trigonometrical operations is given by Port-

A discussion of the priorities is given by C. Wolf (see Note 13b.) who

For trigonometrical activities of the period in general, see: Clarke, A. R.

For the historical context, see Skelton’s chapter on Cartography in Vol.

(1831-33) 19.

14’

188 Gordon Jones

lcxk, J. E., Life of Major-General Colby. (1869) 36. The previous measurement was by Roy (and others) and was reporied in

Philosophical Transactions (1 790) 1 1 1. 37. For a description of the lights see: Drummond. Philosophical Transactions

(1826) pt. 3. 328. 38. Kater gives the reference: Oriani. Opusculi Astronomici, Milan, 1826. We

read also that Baron von Zach used the same formula (R.A.S. Monthly 2, 1831-33, 113.) and the reference he gives is Correspondance Astrono- mique I I (1 805) 550.

39. Annalen der Phvsik und Chemie 14 (1828) 622. 40. Astronomische Nachrichten 7 (1828) col. 49. 41. Arago, F. Oeuvres Complztes 4 (Notices Scientifiques 1) 647. 42. Philosophical Transactions (1 857) 666. 43. The copy I have used is:

( A Treatise on) Mechanics. (Cabinet Cycloprediu). London (1830) 11 by 18 cm. 9 + 342 + 21 pl.

In addition, I have met the following references, none of which I have seen. Mechanics (a new edition).

Mechanics (a new edition).

(A Treatise on) Mechanics.

(A Treatise on) Mechanics. (Cabinet o f Natural Philosophy).

TraitC de Mkcanique. (trad. par Peyrot).

Etudes ilimentaires de Mkcanique. (trad. par Peyrot)

Elkments de Mkcanique. (traduits, modifib et cornplit6s par Cournot. 2e

London (1835) 16" 9 +- 342 + pl.

London (1851) 17 cm. 9 + 342 + pl.

Philadelphia (1832) 17 cm. 8 + 287 + 21 pl.

Philadelphia (1836) 12".

Paris (1834) 8 " 232 + pl.

Paris (1836) 8" 232 + pl.

Uition.) Paris (1842) 12" 23 + 443 + pl.

Quedlinburg (1 835) 8" 16 Taf.

Stuttgart (1836) 8" 21 Taf.

Torino (1851) 12" 12 + 455 + pl.

Lehrbuch der Mechanik.

Lehrbuch der Mechanik. (aus d. Engl. von Kossman.)

Elementi di Meccanica. (18 versione italiana con note ed aggiunte di C.I.G.)

44. Nicholson's Journal 31 (1 8 12) 3 16. 45. Alexander, A. F. O'D. The Planet Saturn. London, 1962. 46. One of those mentioned is Quetelet, who reprinted Kater's observations in

his Correspondances Muthe'matiques 7 (1832) 299. 47. Encke, J. F. Astronomische Nachrichten 15 (1838) col. 18. 48. R. A . S. Monthly Notices. I (1828-31) 177. 49. The reference on page 204 of the article is given wrongly as Phi1.Trans.


50.

51. 52.

53. 54. 55.

56. 57. 58.

1817, probably because the lecture was read in November 1817. The correct reference is PhiLTrans. (1818) 172, and the particular passage considered is on pages 186-7. Kater is named in connection with escapements by Rawhgs, A.L. The Science of Clocks and Watches. London, 1948, page 102. This also includes a bibliography. Astronomische Nachrichten. 4 (1 826) COI. 225-6. Receipt of the collimator is noted: Astronomische Nachrichten. 4 (1 826) col. 311. Mechanics’ Magazine 3 No. 81 (1825) 387. Mentioned in Kater’s report in Philosophical Transactions (1 826) 10. Harding, M. C . Correspondance de H . C . Orsted. Copenhagen, 1920, pp. 422-424. Hansteen, C. Mugazin for Naturvidenskaberne. 4 (1824), 5 (1825). Sijderbaum, H. G. Jac. Berzelius’ Reseanreckningar. Stockholm, 1903, p.116. Somerville, Mrs. M. On the magnetizing power of the sun’s rays. Philoso- phical Transactions (1 826) pt.2, 132.

Documents

The Scientific Publications of Henry Kater