Part 2

Self-recording barometers and thermometers were more vulnerable to the influence of friction than were wind instruments, but fortunately pressure and temperature were also less subject to sudden fluctuation, and so self-registration was less necessary. Nevertheless, two events occurred in the 1840's which led to the development of self-registering instruments. One event was the development of the geomagnetic observatory, which used the magnetometer, an instrument as delicate as the barometer and thermometer, and (as it then seemed), as subject to fluctuation as the wind vane. The other event was the development of photography, making possible a recording method free of friction. In 1845 Francis Ronalds at Kew Observatory and Charles Brooke at Greenwich undertook to develop apparatus to register the magnetometer, electrometer, thermometer, and barometer by photography.[18] This was six years after Daguerre's discovery of the photographic process. The magnetometers of both investigators were put into use in 1847, and the barometers and thermometers shortly after. They were based on the deflection--by a mirror in the case of the magnetometer and electrometer and by the mercury in the barometer and thermometer--of a beam of light directed against a photographic plate. Brooke exhibited his instruments at the Great Exhibition of 1850, and they subsequently became items of commerce and standard appurtenances of the major observatory until nearly the end of the century (fig. 6). Their advantages in accuracy were finally insufficient to offset the inconvenience to which a photographic instrument was subject.

Before 1850 the British observatories at Kew and Greenwich (the latter an astronomical observatory with auxiliary meteorological activity) had self-registering apparatus in use for most of the elements observed.

Self-Registering Systems

In 1870 the Signal Corps, U.S. Army, took on the burden of official meteorology in the United States as the result of a joint resolution of the Congress and in accordance with Joseph Henry's dictum that the Smithsonian Institution should not become the permanent agency for such scientific work once its permanency had been decided upon. Smithsonian meteorology had not involved self-recording instruments, and neither did that of the Signal Corps at the outset "because of the expense of the apparatus, and because nothing of that kind was at that time manufactured in this country."[19]

But almost immediately after 1870 the Signal Corps undertook an evidently well-financed program for the introduction of self-registration. "Complete outfits" were purchased, representing Wild's system, the Kew system as made by Beckley, Hipp's system (fig. 8), Secci's meteorograph (figs. 9, 10), Draper's system, and Hough's printing barograph and thermograph. Of these only the Kew system, the photographic system already mentioned, could have been obtained before 1867.

Like Kew, Daniel Draper's observatory in Central Park, New York City, was established primarily for meteorological observation.[20] Draper was one of the sons of the prominent scientist J. W. Draper. Hipp was an instrument-maker of Neuchâtel who specialized in precision clocks.[21] The others after whom these "systems" were named were directors of astronomical observatories, which were, at this time, the most active centers of meteorological observation. Wild was at the Bern Observatory,[22] Secci at the Papal Observatory, Rome,[23] and George Hough at the Dudley Observatory, Albany, New York.[24] While the Signal Corps seems to have acquired all of the principal "systems," some interesting instruments were developed at still other observatories, notably by Kreil at the astronomical observatory in Prague.[25] The principal impetus for this full-scale mechanization of observation undoubtedly came from the directors of astronomical observatories.

Thus within little more than the decade of the 1860's were developed five new systems of meteorological self-registry that were sufficiently well thought of to be adopted or copied by observatories outside their places of origin. Wild and Draper tell us that it was decided when their respective observatories were established--in 1860 and 1868--that all instruments should be self-registering. Each was obliged to design his own, being dissatisfied with the photographic registers commercially available. The development of these systems would therefore appear to have been due, in part, to the general spread of a conviction that satisfactory instruments were attainable.

This confidence was warranted, for the decade of the 1850's had seen the appearance of major innovations in the basic instruments--thermometer, barometer, and wind velocity indicator--that made available instruments more adaptable to self-registration. It also saw the development of a new method of electrical registration derived from the telegraph. Sir Charles Wheatstone initiated this small revolution in 1843 when he reported to the British Association that he had constructed an electromagnetic meteorological register which "records the indications of the barometer, thermometer and the psychrometer [meaning wet-bulb thermometer] every half hour ... and prints the results on a sheet of paper in figures," running a week unattended. The working of this register involved the insertion of a conductor in the tubes to make a circuit, the thermometers having open tops.[26] This was ten years after the development of the electromagnetic relay and six years after Wheatstone's introduction of his own telegraph.

Wheatstone's instrument left a very ephemeral record in the meteorological literature, and appears to have been defective or out of fashion with its time, which was concerned with the introduction of photographic instruments. Wheatstone's work was rediscovered, along with that of several other much earlier inventors, by the determined observatory directors of the 1860's.

Of the five systems developed at that time, four used electromagnetic registration, only Draper adhering to a mechanical system (see fig. 11). For temperature measurement Secci and Hough used Wheatstone's electrical system with a mercurial thermometer (fig. 12), but the other four utilized a physical principle which had been proposed periodically for at least a century--the unequal thermal expansion of a bimetallic strip. This principle had been utilized by watchmakers for a quite different purpose--the temperature compensation of the watch pendulum--but its possibilities as a thermometer had been known long before the mid-19th century.[27]

For the measurement of pressure, Secci, Wild, and Draper adopted, or rediscovered, the balance barometer devised by Wren in the 17th century. In this type of instrument (see figs. 13, 15) either the tube or the reservoir of the barometer is attached to one arm of a balance, the equilibrium of which is disturbed by the movement of the mercury in the instrument.[28]

Hough's barometer was an adaptation of the electrical contact thermometer. The movement of the mercury over a certain minute distance within the tube served as a switch to energize an electrical recording system. Hipp, who was perhaps the latest of this group, first applied the aneroid barometer (fig. 8) to self-registration. The idea of the aneroid--an air-tight bellows against which the atmospheric pressure would act--had been advanced by Leibniz in the 17th century and had been the subject of a few abortive experiments in the 18th century. Not until 1848 was an instrument produced that was acceptable to users of the barometer.[29]

As a wind velocity instrument all six systems used the cup-anemometer developed by Robinson in 1846, an instrument whose chief virtue was the care which its inventor had taken to work out the relationship between its movement and the actual velocity of the wind.[30] Beckley and Draper caused it to move a pencil through gearing; the others used with it electromagnetic counters actuated by rotating contacts.

As has been indicated, the Signal Corps used all six systems, a panoply of gadgetry which must have been wondrous to behold. Its Secci meteorograph, which had attracted much attention at Paris, was estimated to have cost 15,000 francs. Abbe reported in 1894 that the instruments were long kept in the apparatus room "as a fascinating show to visitors and a stimulation to the staff in the invention of other instruments."[31]

From 1875 the question was no longer one of the introduction of self-registering instruments to major observatories but their complete mechanization and the extension of registration to substations. Having accepted self-registration, meteorologists turned their attention to the simplification of instruments. In 1904 Charles Marvin, of what is now the U.S. Weather Bureau, brought the self-registering barometer into something of a full circle by producing an instrument (fig. 14) that was nothing more than Hooke's wheel barometer directly adapted to recording.[32] But this process of simplification had been accomplished at a stroke, about 1880, with the introduction by the Parisian instrument-maker Jules Richard of a self-registering barometer and a thermometer combining the simplest form of instrument with the simplest form of registration (see fig. 16). This innovation, which fixed the form of the conventional registering instrument until the advent of the radiosonde, seems to have stemmed from a source quite outside meteorology--the technology of the steam gauge. Richard's thermometric element was the curved metal tube of elliptical cross-section that Bourdon had developed several decades earlier as a steam gauge. Pressure within such a tube causes it to straighten, and thus to move a pointer attached to one end. Bourdon had opened it to the steam source. Richard filled it with alcohol, closed it, and found that the expansion of the alcohol on heating caused a similar straightening. His barometric element was a type of aneroid, which Hipp had already used but which Richard may have also adopted from a type of steam gauge. For a recording mechanism, Richard was able to use a simple direct lever connection, as the forces involved in his instruments, being concentrated, were not greatly hampered by friction.[33] By 1900 these simple and inexpensive instruments had relegated to the scrap pile, unfortunately literally, the elegant products of the mass attack of observatory directors in the 1860's on the problem of the self-registering thermometer and barometer.[34]

Conclusions

In view of the rarity of special studies on the history of meteorological instruments, it is impossible to claim that this brief review has neglected no important instruments, and conclusions as to the lineage of the late 19th century instruments can only be tentatively drawn. The conclusion is inescapable, however, that the majority of the instruments upon which the self-registering systems of the late 19th century were based had been proposed and, in most cases, actually constructed in the 17th century. It is also evident that in the 17th century at least one attempt was made at a system as comprehensive as any accomplished in the 19th century.

To attribute the success of self-registering instruments in the late 19th century to the unquestionable improvements in the techniques of the instrument-maker is to beg the question, for it is by no means clear that the techniques of the 17th-century instrument-maker were unequal to the task. It should also be noted that the photographic and electromagnetic systems of the 19th century seem to have been something of an interlude, for some of the latest and most durable (all of Draper's and Richard's instruments and Marvin's barograph) were purely mechanical instruments, as had been those of Hooke and Wren. If we conclude that the 19th-century instruments were more accurate, we should also recall Forbes' comments upon the question of instrumental accuracy.

What, then, was the essential difference between the 17th and 19th centuries that made possible the development of the self-registering observatory? It would appear to have been a difference of degree--the maturation in the 19th century of certain features of the 17th. The most important of these features were the spread throughout the western world of the spirit that had animated the scientific societies of Florence and London, the continued popularity of the astronomical observatory as an object of the philanthropy of an affluent society, and the continued existence of the nonspecialized scientist. Under these circumstances such nonmeteorologists as Wheatstone, Henry, Hough, Wild, and Secci had the temerity to range over the whole of the not yet compartmented branches of science and technology, fully confident that they were capable of finding thereby a solution to any problem important enough to warrant their attention.

FOOTNOTES:

[1] On early meteorological instruments see A. Wolf, _A History of Science, Technology and Philosophy in the Sixteenth and Seventeenth Centuries_, New York, 1935, and E. Gerland and F. Traumüller, _Geschichte der physikalischen Experimentierkunst_, Leipzig, 1899. On the recognition of the meteorological significance of the barometer by Torricelli and its meteorological use in 1649 see K. Schneider-Carius, _Wetterkunde Wetterforschung_, Freiburg and Munich, 1955, pp. 62, 71.

[2] Bacon's book emphasizes "direct" and "indirect" experiments, and calls for the systematization of observation, but it does not mention instruments. It is reprinted in Basil Montagu's _The Works of Francis Bacon, Lord Chancellor of England,_ London, 1825, vols. 10 and 14.

[3] Wolf, _op. cit._ (footnote 1), pp. 312, 316-320. The interest of the Royal Society in the barometer seems to have been initiated by Descartes' theory that the instrument's variation was caused by the pressure of the moon.

[4] _On early meteorology in the United States see the report of Joseph Henry in Report of the Commissioner of Patents, Agriculture, for the Year 1855_, 1856, p. 357ff.; also, _Army Meteorological Register for Twelve Years, 1843-1854_, 1855, introduction.

[5] J. D. Forbes, "Report upon the Recent Progress and Present State of Meteorology," _Report of the First and Second Meetings of the British Association for the Advancement of Science, 1831 and 1832_, 1833, pp. 196-197.

[6] On the instruments used at Mannheim see Gerland and Traumüller, _op. cit._ footnote 1, p. 349ff. The Princeton physicist Arnold Guyot prepared a set of instructions for observers that was published in _Tenth Annual Report ... of the Smithsonian Institution_, 1856, p. 215ff. It appears from the _Annual Report of the British Association for the Advance of Science_ in the 1830's that the instruments used in England were nearly the same as those later adopted by the Smithsonian, although British observatories were beginning to experiment with the self-registering anemometer at that time. A typical set of the Smithsonian instruments is shown in figure 1.

[7] H. Alan Lloyd, "Horology and Meteorology," _Journal Suisse d'Horlogerie_, November-December, 1953, nos. 11, 12, p. 372, fig. 1.

[8] R. T. Gunther, _Early Science in Oxford_, vol. 6, _The Life and Work of Robert Hooke_, pt. 1, Oxford, 1930, p. 196. In 1670, Hooke's proposed clock was referred to as "such a one, as Dr. Wren had formerly contrived" (Gunther, p. 365).

[9] William Derham, _Philosophical Experiments and Observations of ... Dr. Robert Hooke_, London, 1726, pp. 41-42 (reprinted in Gunther, _op. cit._ footnote 8, vol. 7, pp. 519-520). This description, dated December 5, 1678, predates the Royal Society's request for a description (Gunther, _op. cit._ footnote 8, p. 656) by four months, but the Society no longer has any description of the clock. As to the actual completion of the clock, the president of the Society visited "Mr. Hooke's turret" to see it in January of 1678/79 but it was not reported "ready to be shown" until the following May (Gunther, pp. 506, 518).

[10] Wren's clock and its wind vane and anemometer, thermometer, barometer, and rain gauge are described by T. Sprat, _The History of the Royal Society..._, London, 1667, pp. 312-313. On the balance-barometer, see also footnote 28, below, and figure 4.

[11] Since the above was written, additional information on this clock has been published by H. E. Hoff and L. A. Geddes, "Graphic Recording before Carl Ludwig: An Historical Summary," _Archives Internationales d'Histoire des Sciences_, 1959, vol. 12, pp. 1-25. Hoff and Geddes call attention to a report on the clock by Monconys, who saw the instrument in 1663 and published a brief description and crude sketch (Balthasar Monconys, _Les Voyages de Balthasar de Monconys; Documents pour l'Histoire de la Science, avec une Introduction par M. Charles Henry_, Paris, 1887). Monconys says that the thermometer "causes a tablet to rise and fall while a pencil bears against it." The instrument shown in his sketch resembles a Galilean thermoscope.

[12] Hooke's "oat-beard hygrometer" was described in 1667, but Torricelli seems to have invented the same thing in 1646, according to E. Gerland, "Historical Sketch of Instrumental Meteorology," in "Report of the International Meteorological Congress Held at Chicago, Ill., August 21-24, 1893," O. L. Fassig, ed., _U.S. Weather Bureau Bulletin No. 11_, pt. 3, 1896, pp. 687-699.

[13] But a Dutch patent was awarded to one William Douglas in 1627 for the determination of wind pressure (G. Doorman, _Patents for Inventions in the Netherlands during the 16th, 17th and 18th Centuries_, The Hague, 1942, p. 127), and Leonardo da Vinci left a sketch of both a wind pressure meter and a hygrometer (_Codex Atlanticus_, 249 va and 8 vb).

[14] Gunther, _op. cit._ (footnote 8), pp. 433, 502.

[15] Battista della Valle, _Vallo Libro Continente Appertiniente ad Capitanii, Retenere and Fortificare una Citta..._, Venetia, 1523 (reported under the date 1524 in G. H. Baillie, _Clocks and Watches, an Historical Bibliography_, London, 1951).

[16] Dolland's instrument, called an "atmospheric recorder," is described in the _Official, Descriptive and Illustrated Catalogue to the Great Exhibition, 1851,_ London, 1851, pt. 2, pp. 414-415. As the George Dolland who joined the famous Dolland firm in 1804 would have been about 80 years of age in 1850, the George Dolland who exhibited this instrument may have been a younger relative.

[17] The Osler anemometer and most of the other self-registering instruments mentioned in this paper are described and illustrated in C. Abbe, "Treatise on Meteorological Apparatus and Methods," _Annual Report of the Chief Signal Officer for 1887_, Washington, 1888. The use of the Osler instrument at the British Association's observatory at Plymouth is mentioned in the Association's annual reports from 1838. There were a number of earlier self-registering anemometers, but no evidence of their extended use. See J. K. Laughton, "Historical Sketch of Anemometry and Anemometers," _Quarterly Journal of the Royal Meteorological Society_, 1882, vol. 8, pp. 161-188.

[18] On Ronalds' work see reports of the British Association for the Advancement of Science, from 1846 to 1850. On Brooke's work see _Philosophical Transactions of the Royal Society of London_, 1847, vol. 137, pp. 59-68.

[19] C. Abbe, "The Meteorological Work of the U.S. Signal Service, 1870 to 1871," in Fassig, _op. cit._ (footnote 12), pt. 2, 1895, p. 263.

[20] _Annual Report of the Director of the Meteorological Observatory_, Central Park, New York, 1871, p. 1ff.

[21] _Oesterreichische Gesellschaft für Meteorologie, Zeitschrift_, 1871, vol. 6, pp. 104, 117.

[22] P. H. Carl, _Repertorium für physikalische Technik_, Munich, 1867, p. 162ff.

[23] E. Lacroix, _Études sur l'Exposition de 1867_, Paris, 1867, vol. 2, p. 313ff. See also, Reports of the U.S. Commissioners to the Paris Universal Exposition, 1867, vol. 3, Washington, 1870, p. 570ff.

[24] _Annals of the Dudley Observatory_, 1871, vol. 2, p. vii ff.

[25] Karl Kreil, _Entwurf eines meteorologischen Beobachtungs-Systems für die österreichische Monarchie_, Vienna, 1850.