PAPER BY PROF. BEZOLD. 253 



ascending whirl, masses of air are always drawn in from one side that 

 had not yet sunk to the earth's surface and had remained correspond- 

 ingly unaffected by the radiation and absorption that have their seat in 

 that stratum, and which also had had no opportunity to take up water 

 from the earth's surface. Since these masses of air coming from the 

 upper portions of the anticyclone have in general higher potential and 

 therefore also higher absolute temperature than the portions of the 

 cyclone lying at equal altitudes above sea level, therefore the mixture 

 of these will diminish the cooling of the ascending air and both there- 

 by as also by reason of the lesser quantity of water that they possess, 

 will delay the occurrence of condensation. 



Therefore in the cyclone itself the vertical temperature gradient even 

 beneath the clouds will not be so large as one would expect according 

 to the law of the adiabatic changes for the dry stadium without mix- 

 ture of foreign masses of air. Similar relations obtain, although not 

 to an equally great extent, with regard to the descending current, which 

 in its upper half is also fed by portions of the cyclone in which the con- 

 densation has not yet gone so far and has not yet attained the high 

 potential temperature of the highest stratum concerned in the whole 

 process. Therefore in reality both the ascending and the descending 

 branches of the curve deviate from the schema of Figure 36, and in both 

 of them the vertical gradient will more or less approximate the average 

 as we find it when we consider the ascent and descent as a connected 

 whole. 



These considerations are entirely in accord with observed facts. 

 Even when we deduce the vertical temperature gradient from observa- 

 tions at stations of which the upper one is not so high that it is fre- 

 quently within the clouds, we attain to temperature gradients that in 

 general are far less than that computed for the dry stage ; this result 

 is in great part only explicable as due to the above described mixture. 

 The observations of the clouds also agree perfectly with what has been 

 said, both with regard to the temperature conditions and the moisture. 



Only the central part of the cyclone is to any considerable extent fed 

 by masses of air that have flowed along the surface of the earth itself, 

 as one can easily convince himself by a simple diagram ;* whereas the 

 periphery receives more and more air from the higher strata, whereby 

 its lower boundary surface is raised but its power must be diminished. 

 In fact also the clouds at the center of the cyclone hang down the 

 lowest and are higher near the circumference, exactly as is demanded 

 by the moisture conditions and the higher potential temperature of the 

 intermixed masses of air. The friuge of clouds that we perceive 

 beneath the layer of clouds that covers the sky (especially on wooded 

 hills during the prevalence of a cyclone) and in which we can clearly 

 follow the ascent of air in inclined paths, gives in connection with the 



See, for example, Mohn, Grundzuge, 3d edition, ISS3, p. 261. 



