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.

Figure 6.—Photographic registering mercurial barometer, typical commercial version. (From J. J. Hicks, Catalogue of ... Meteorological Instruments, London, n.d., about 1870.)

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.

Figure 7.—In 1838 the pioneer American meteorologist James H. Coffin (1806-1873) devised a self-registering wind direction indicator; in 1849 he improved it as shown here. The band, moved by clockwork, carries cards marked with the day and hour. In Coffin's earlier instrument, a part of which is now in the Smithsonian Institution, the vane carried a funnel for sand, which ran into a circular row of bottles. (From Proceedings of the American Association for the Advancement of Science, 1849, vol. 2, p. 388.)

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