RECENT SCIENCE. 395 



which, fully deserves being widely known. All taken, his views 

 so well agree with the facts relative to the movements of the at- 

 mosphere, and they give such a sound method for further investi- 

 gation, that they are sure to become for some years to come the 

 leading theory of meteorology. They already have given a strong 

 impulse to theoretical research, and have created a whole litera- 

 ture in Austria and Germany.* 



Another theory of the general circulation of the atmosphere 

 which is also awakening a good deal of interest among physical 

 geographers was propounded in 1886 by Werner Siemens, and 

 further developed by him in 1890. \ Siemens did not consider 

 that air might flow down the density surfaces, as supposed by 

 Ferrel and Helmholtz, and admitted by many meteorologists, and 

 he maintained that the source of the energy required for all dis- 

 turbances of equilibrium in the atmosphere must be looked for in 

 the unequal heating of its different strata by the sun, and in the 

 unequal loss of heat through radiation in space. From these 

 considerations he inferred the existence of an ascending current 

 in the equatorial belt, an upper warm current, and a cold polar 

 current. As to the eastward and westward directions of these 

 currents, he made the very just remark that the energy of rota- 

 tion of the whole atmosphere must remain constant and un- 

 changed, even though masses of air move from one latitude to 



* Roth has already abandoned the mathematical objections he had raised against Fer- 

 rel's theory in the Wochenschrift fur Astronomie, 1888. The objections raised by Teis- 

 serene du Bort and Supan against the " density surfaces " have been answered by Prof. 

 Davis in Science, and are not shared by the most prominent meteorologists. And the 

 mathematical analysis of Prof. Waldo, Sprung (the author of the well-known Treatise of 

 Meteorology), M. Holler, and Pernter has further confirmed the accuracy of the theory. 

 So also Hildebrandsson's observations of upper clouds (Annuaire de la Societe meteoro- 

 logique de France, xxxix, 338), Teisserenc du Port's high-level isobars, and Guaran de 

 Trommelin's researches relative to coast winds. The transport of the Krakatoa dust and 

 Abercromby's observations of clouds having rendered the existence of an upper east cur- 

 rent very probable on the equator, Pernter has mathematically deduced from Ferrel's the- 

 ory the existence of such a current in a belt 4° 45' wide on both sides of the equator, and 

 he therefore has withdrawn the restrictions he had previously made in a lecture (published 

 in Nature, 1892, xlv, 593) in favor of Siemens's views. It must be added that the idea of 

 three superposed currents blowing in spirals may have been suggested to Ferrel by a com- 

 munication of James Thomson to the British Association in 1857. Such was, at least, the 

 claim raised and developed at some length by the Glasgow professor before the Royal 

 Society in a Bakerian lecture, now published in the Transactions (A. 1892, pp. 653-685). 

 Though Thomson's paper was never published, and only given in a very short abstract with- 

 out a diagram (the diagram in the Transactions is now published for the first time), the few 

 lines in which his theory was stated (British Association Reports, Dublin, 185*7, pp. 38, 39) 

 contained the idea clearly expressed. It is certainly a matter of great regret that James 

 Thomson has not returned to this subject. 



f Ueber die Erhaltung der Kraft im Luftmeere, in Sitzungsberichte der Berliner Aka- 

 demie der Wissenschaften, March, 1886, p. 261 ; Ueber das allgemeine Windsystem der 

 Erde, in same publication, 1890, ii, p. 629. 



