DYNAMIC METEOROLOGY. 385 



" The motions in the atmosphere have been further treated of by C. M. 

 Guldberg and H. Mohn. (Studies on the Motions of the Atmosphere, 

 Christiania, part i, 1876, part ii, 1880.) These authors both start with 

 the correct hydrodynamic equations. The motions are by them directly 

 recorded in differences of pressure. Furthermore, the resistance is 

 assumed to be proportional to the velocity of the wind then prevailing?. 

 It is very probable that this assumption is appropriate for the lowest 

 strata of the atmosphere. The calculations of the above-named scholars 

 will, therefore, lead also to results that agree with observations in gen- 

 eral for the movement of the air in the neighborhood of the earth's sur- 

 face, esjiecially when we carry through the computations somewhat 

 more accurately, as was done by me a short time ago. (See Wiede- 

 mann Annalen, 1882, vol. xvii, p. 128, reproduced in No. 7 of the 

 accompanying translations; compare also A. Sprung, Treatise on 

 Meteorology, pp. 142-151.) On the other hand, there can certainly 

 be no doubt that the above-given assumption as to the nature of the 

 frictional resistance is entirely inappropriate for the upper strata of 

 air. A general comprehensive theory of cyclones, in which the upper 

 and the lower currents are considered, and in which, furthermore, the 

 fundamental cause of cyclones, namely, local differences of density in 

 the atmosphere, occupies the foreground, can certainly not be attained 

 by using the above-mentioned assumption as to resistance. 



"The problem of the progressive movement of cyclones, so remarkably 

 important but at the same time so very difficult, can indeed only first 

 find a satisfactory solution when (1) the constitution of a stationary 

 cyclone is sufficiently well known (2) the curreuts in the upper strata 

 of the atmosphere are established with some degree of certainty. 



"The above mentioned investigations are presented in a clear and com- 

 prehensive form in the treatise on meteorology by A. Sprung, Ham- 

 burg, 1885. 



"Especially would I call attention to the judgment of the author as to 

 W. Ferrel (page 198 and notes on pages 200 and 202), with which I 

 entirely agree.* 



" Since that publication the motions of the atmosphere have been 

 treated by W. Siemens, introducing the fundamental propositions of the 

 conservation of energy. (Siemens, On the Conservation of Energy in 

 the Atmosphere of the Earth. Sitzungsberichte of the IJerlin Academy, 

 1886, p. 261). This author, without special analytical developments, 

 makes the existence of strong currents in the direction of the parallels 

 of latitude very probable, and ascribes to them a predominant influence 

 on even the wind systems of the temperate zones. 



* Sprang's criticism is but little more than the opinion of a regret that Ferrel has 

 not fully solved the equation of coutinuity, but as he has adopted tho special solution 

 that is offered by the mean distribution of temperature and pressure in the earth, I 

 do not see that any error has been introduced thereby. — (J. A. 



H. Mis. 142 25 



