SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 39 1 



D. 



THE LAWS OF THE VARIATION OP TEMPERATUEE IN 

 ASCENDING CUEKENTS OF AIE, AND SOME OF THE MOST 

 IMPORTANT CONSEQUENCES DEDUCIBLE THEEEFEOM. 



Bv Dr. J. IIaxx. 



[Translated by Cleveland Abbe from Zeit. Oest. Gesell. Met., 187-1, ix, pp. 301 et seq] 



Only in the last ten years have we really begun to fully credit and 

 establish physically the great importance of the ascending movement 

 of air for a whole series of atmospheric phenomena. This, for instance, 

 can be clearly seen when we seek to collect the sentences relating to the 

 ascending currents in the carefully and comprehensively compiled Lehr- 

 buch of E. E. Schmidt, Leipsic, 1860. Notwithstanding that the cool- 

 ing of ascending air in consequence of expansion could long since have 

 been computed by means of an equation deduced by Poisson, still we 

 have made only fruitless efforts in its application to atmospheric phe- 

 nomena, and, for instance, have sought to explain the precipitation on 

 the flanks of a mountain over which a warm current is blowing mostly 

 by the contact of the rising air with the cool earth, also by the mixture 

 of the air with the higher colder strata. Evidently, it has beeu con- 

 sidered not quite certain how far the equation of Poisson is applicable 

 to the processes in the free atmosphere ; for there was no appropriate 

 example at hand by means of which to demonstrate quantitatively the 

 diminution of temperature with altitude in accordance therewith. The 

 minute study of the Fohn phenomena first led to such knowledge, and 

 showed the difference of temperature demanded by the theory between 

 the lower and upper strata of a descending current of air and the cir- 

 cumstances which enforced the recognition of the connection between 

 cause and effect.^ The theory of ascending movements of air has, how- 

 ever, experienced a very important advance through the labors of cer- 

 tain physicists (W. Thomson, Eeye, Peslin), who have deduced from the 

 principles of the mechanical theory of heat the laws of the variation of 

 temperature in ascending or descending dry or moist masses of air. 



In our Zeitschrift we have as yet presented no report on these important 

 labors, and as they have also not as yet been presented in the physical 

 or meteorological text-books, we consider it i)roper here to explain and 

 to deduce the most important propositions in the simplest manner pos- 

 sible. 



1. 



The Amount of the Diminution of Ternperature in Ascending Currenis of 

 Air in tchich no Condensation of Vapor occurs. 



Let dQ denote a very small quantity of heat imparted to or abstracted 

 from a unit weight of air j 

 c, the specific heat of air at constant pressure = 0,2375 ; 



