PAPER BY PROF. BEZ(3LD. 213 



that one always runs in danger of losing the leading thought in the 

 midst of the notation and signs. 



But in consideration of the fundamental importance that the applica- 

 tion of the mechanical theory of heat in the most comprehensive maa- 

 Der i)ossesses for the development of -meteorology, one evidently ought 

 DOt to be frightened by these extreme difficulties. This has induced me 

 to make the attempt to introduce a method into meteorology that has 

 proved so remarkably fruitful iu the ap[)lication of the mechanical 

 theory of the heat to the theory of machines : I mean the graphic 

 method that Clapeyrou* has invented in order to make the ideas first ex- 

 pressed by Sadi Carnott visible and comprehensible. Already, some 

 years ago, a step in a similar direction was taken by Hertzf in a highly 

 meritorious work on a graphic method for the determination of the 

 adiabatic changes in moist air; but the problem that Hertz had before 

 him, as also the method which he adopted, were materially different 

 from those that I have now in mind. On the one hand, Hertz confined 

 himself, as his title states, exclusively to the consideration of the adia- 

 batic changes, and on the other hand, his object was only by means of 

 a siuiple graphic process to avoid the complicated computations that 

 one has to execute in following these changes. My object, on the other 

 hand, has been to give a method of presentation that can serve as a guid- 

 ing thread iu the still more complicated formulas with which one has to 

 compute as soon as we disregard the restrictive assumption of adiabatic 

 change, and that also allows one to draw certain important conclusions 

 even from the form of the geometrical figures. To attain these objects 

 however, scarcely any mental presentation is so appropriate as that in- 

 troduced into science by Clapeyrou, of course with such extensions as 

 are required by the condition that iu meteorologi(!al problems we have 

 not as there to consider only two independent variables, but three, or 

 in special cases, even still more. 



But before I enter upon the subject itself I must touch upon another 

 point on which notwithstanding itstundameutal importance, remarkable 

 to say, still perfectly clear views do not prevail. This has respect to 

 the true reason of the cooling that occurs iu the ascent of air to higher 

 regions as well as the correspouding warming for descend] ug air. 

 While Sir William Thomson, § Keye,|| Hauu,^] Pesliu,** and with these 

 investigators probably also the greater part of all physicists and meteor- 

 ologists, correctly consider the cooliugof ascending air as a consequence 

 of the expansion occurring therein, ou the other hand, Giililberg and 



"Poggeudorff's ^«naZeft, vol. 59, pp. 446-566. 

 ^Reflexions siir la puissance motrice dufeu. Paris, 1824. 



t Me'eorologisihe. Zeit., 1834, i, pp. 421-431. [See No. xiv of this collection.] 

 $ Proc. of Manchester Soc, 1862, li, 170-176. 

 \\Die Wirbelstiirme, Hannover, 1872. 



11 Zeitschrift d. Oesterr. Ges. f. Met., 1874, Bd. ix, pp. 321, 337. 8mithson. Rep. 1877, 

 p. 397. 



* * liitU. Itelid. de V Assoc, scientif. dc France, 1868, Tome in, p. 299. 



