physicists. Those who have, since 1850, contributed most to our knowledge of the mechanics and physics of the atmosphere may be enumerated as follows: Adolph Erman, who published in 1868 a memoir on the distribution of winds and pressure over the globe; J. C. Redfield, who showed the mechanism of extended hurricanes; James P. Espy, who published several reports and a volume on the philosophy of storms, explaining in general how atmospheric moisture, by its condensation into cloud and rain, disturbs the equilibrium of the atmosphere and produces both local and general storms; William Ferrel, who published numerous papers developing the laws of the motions of the earth's atmosphere and its general and local phenomena as resulting from the rotation of the earth on its axis, the evaporation and condensation of aquaeous vapor, and the general influence of the solar heat; Lord Kelvin, who first gave the laws of thermal convective equilibrium for dry air; Peslin, who gave the laws of thermal equilibrium for moist air; Von Helmholtz, Willy Wien, Oberbeck, Guldberg and Mohn, Margules, Diro Kitao, Rayleigh, Pockels, Sprung, and F. H. Bigelow have made important contributions to the hydrodynamic problems of the atmosphere; Prof. H. Hertz, W. von Bezold, and Marcel Brillouin have contributed greatly to the perfection of our knowledge of the thermodynamic problems. The most recent contributions in this field include that of Pockels, on the Theory of the Formation of Rain in slowly ascending currents of moist air (see Wiedemann's Annalen, January, 1901); Prof. F. H. Bigelow's tables in his reports on International Cloud Work (Washington, 1900); his report on Barometry (Washington, 1902); Neuhoff's memoir on Adiabatic Changes in the Atmosphere (Berlin, 1900); Berson and Assmann's Scientific Balloon Ascensions, 3 vols., quarto (Berlin, 1900); all which respectively contain highly important investigations.
WEATHER MAP FOR MONDAY, APRIL 4, 1892, 8 A.M.
Our knowledge of meteorological conditions has been obtained for the most part by observation of the clouds or by stations on mountain tops. More recently it has been found desirable to study conditions at considerable altitudes above stations and places. In order to obtain better data for the lower atmosphere, at least partially to meet the needs of the case, Americans have developed the art of obtaining meteorographic records by sending up meteorographs on kites to heights of one or two miles; on the other hand, Europeans have given attention to the development of the balloon and especially the small sounding balloon which can carry a meteorograph to an elevation of six or eight miles above sea level, where man cannot live. The exposure of meteorological apparatus so that the records from different stations on the earth's surface and from vessels on the ocean and from kites or balloons in the atmosphere shall be comparable with each other offers many difficult problems, but the progress toward uniformity throughout the world has been appreciable during the past twenty-five years. Every first-class weather service now keeps close watch of the condition of its apparatus and the correctness of the methods in vogue at its stations. Although much remains to be done, yet the contrast between the condition of affairs in 1850 and that in 1900 is very great, and the present outlook is very encouraging.
In some cases the larger portion of the funds and forces of a weather service is spent upon observations and climatological work, but in most cases the daily forecast work takes precedence, since that promises immediate results in saving life and property. In order to carry on this work properly, numerous stations must be connected by telegraph with the central bureau, at which several simultaneous observations must be received daily from the observers, and weather charts must be promptly made out showing the
