PAPER BY PROF. BEZOLP. 251 



This again is most simply done by the introduction of the idea of 

 the potential temperature. We can, namely, bring together all of the 

 considerations just expounded into the following theorems: 



(1) If the potential temperature above and below is the same i. e., con- 

 stant throughout the whole layer of air under consideration, then the ver- 

 tical temperature gradient has the well-known value n = v. 



(2) If the potential temperature in the upper stratum is higher than in 

 the lower stratum {and this is in general the case), then is the temperature 

 gradient smaller, and smaller in proportion as for a given difference in 

 altitude, the difference of the potential temperatures is larger. 



If we indicate the potential temperature of tbe upper stratum by T s 

 and that of the lower stratum by T u then for T 8 >T; we shall always 

 have »0 and in fact the differences T a —Ti and r— n always increase 

 simultaneously. 



A decided cooling in the lowest stratum alwajs causes a diminution 

 of T; and with it also a diminution of n, whereby even a change in the 

 sign of n may occur within moderate altitudes. In the latter case, the 

 temperature below is lower than in somewhat higher layers, and in 

 that case we have the so called inversiou of temperature. If the cool- 

 ing is not sufficiently strong to bring about an actual inversion of the 

 temperature, still it causes a diminution of the gradient. Such decided 

 cooling always takes place in the lowest stratum at the time of increased 

 radiation, therefore especially in the region of the anti-cyclone, i. e., 

 uuder a clear sky, in winter, and in the night time. Therefore in the 

 winter and in the night-time the vertical temperature gradient must be 

 smaller than during the summer and day-time, even if inversion in the 

 distribution of temperature does not occur. This result agrees perfectly 

 with observations, as is especially proven by the many facts that 

 Harm and others have collected from the Alpine regions. 



On the other hand the investigation here carried out teaches that the 

 inversion of temperature and the diminution of vertical gradient con- 

 nected therewith are to be treated not as phenomena peculiar only 

 to the mountain regions, but that we are to expect them also above the 

 plains, and even above the ocean, at least insofar as the more violent 

 movements of the air do not interfere therewith. 



We are therefore obliged to agree with Woeikoff* when he from a 

 few data draws the conclusion that this inversion is also to be expected 

 in the region of the great winter anti-cyclone of eastern Siberia. 



On the other hand I can not agree with him when he deduces from 

 this the consequence that Messrs. Wild and Hann should have consid- 

 ered this circumstance in drawing their isotherms, and I consider the 

 standpoint taken by them as perfectly justified. t 



* Woeikoff", Klimate der Erde, German edition, 1887, Bd. n, p. 322; Mcteorolo- 

 gische Zeitschrift, 1884, Bd. I, p. 443. 



t Hanu, Atlas der Met., 1887, p. 5. Wild, Repert., 1888, Bd. xi, Nr. 14. 



