XVII. 



ON THE THERMO-DYNAMICS OF THE ATMOSPHERE. 



(THIKn COMMUNICATION.) 



Ev Prof. WiLHELM VON Rezold. 



In the two ]iapers ]irevionsly published on the above subject the re- 

 strictive assnmption has been always made that the masses of air under 

 consideration experience no mixture with similar masses having other 

 temperatures and other degrrees of moisture. At the same time how- 

 ever it was shown that such mixtures must frequently occur in nature 

 and that the investigations in question could possess only a restricted 

 api>lication so long as we neglect these processes. 



For this reason therefore it is now necessary to extend the previous 

 investigations in this direction. 



But investigations on this subject have also a special interest because 

 for a long time we formerly attributed too much importance to the mix- 

 ing of masses of air of unequal temperature and near the point of sat- 

 uration, whereas in more recent times we have gone to the opposite 

 extreme and attributed to it scarcely any importance at all. 



Following the example of James Hutton,t the mixture of such masses 

 of air was, until within a few decades of years, considered as the prin- 

 cipal cause of atmosjiheric precipitation. 



Wettstein was (so far as I know) the first to antagonize this viewf 

 which however even to-day is still widely accepted. 



He however fell into the opposite error in that he contended tha*:, in 

 general, precipitation never could occur by mixing. 



Here, as in so many other points of modern meteorology, Hann§ first 

 made the matter clear in that he, in the year 1874, proved that by mix- 

 ture condensation could be indeed produced, but that the former method 

 of computing the quantity of precipitation was affected by an error in 

 principle after correcting for which the values obtained are so small 



* Read before the Academy of Sciences at Berlin, October 17, 1889. [Translated 

 from the Sifzungsherichie der Kbnig. Preus. Alcad. der TVissensohaften zu Berlin, 1890, 

 pp. 355-390.1 



t Eoy. Soc. Edinh. Travn., 1788, Vol. i, pp. 41-8(5. 

 t Vierteljahrss. d. naturf. Gesell. Ziirich, 1869, xiv, pp. 60-103. 



§ Ztschft. Oesterr. Gesell. Met., 1874, Vol. ix, pp. 292-29C. [liep. Smithson., 1877, p. 

 385.J 



257 

 80 A 17 



