XVII. 



ON THE THERMO-DYNAMICS OF THE ATMOSPHERE. 

 (THIRD COMMUNICATION. ) 



By Prof. Wilhelm vox Bezold. 



In the two papers previously published on the above subject the re- 

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

 consideration experience no mixture with similar masses having other 

 temperatures and other degrees 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 

 application 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 atmospheric precipitation. 



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

 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 

 front the SitsungsbericMe der Konig. Preus. J had. der Wissenschaften zu Berlin, 1890, 

 pp. 355-390. J 



t Uoy. Soc. Edinh. Travs., 1788, Vol. i, pp. 41-86. 



t I'ierleljahrs.s. d. naturf. Gesell. Ziirich, 18<>9, XIV, pp. 60-103. 



\n Ztschft. Oeaterr. GeselL Met., 1874, Vol. IX, "pp. 292 r 29C. [Hep. Smithson., 1877, p. 



385.1 



257 



80 A 17 



