PAPER BY PROF. BEZOLD. 



245 



designate by i\, and T,. those corresponding to the initial condition a) 

 by combining tlie equation of the adiabatic 



PaV a=PoV"' , 



■with tlie equation of elasticity 



and we thus obtain 



PaVa 



T' 



= R* 



T = (P" 



where h = 1.41.* 



But this simple method of consideration is only allowable so long as 

 the changes of condition take place within the dry stage. If this stage 

 is left then the potential temper- 

 ature belonging to a definite intial 

 point has no longer a constant 

 value, bnt it increases with the 

 quantity of precipitation that is 

 lost. A glance at the figure suf- 

 fices to show this : 



Assuming that the adiabatic of 

 the dry stage drawn through a 

 intersects the dew-point curve 

 (which for simplicity is not shown 

 in the figure) in b and that we now 

 allow the air to still further ex- 

 pand, then one has to pass from b 

 down along the adiabatic (or 

 pseutlo-adiabatic) of the rain or snow stage, that is to say along be. 



If now we seek the potential temperature for a point, c, of this line 

 (in order to simplify the figure I have drawn the line bo only just to 

 this point), in that we bring it again adiabatically to the normal pres- 

 sure, then one ought not to run back along the curve be, since on ac- 

 count of the precipitated water the conditions represented by this por- 

 tion of the line are not again attainable, but on the other hand one can 

 only attain to the line of normal pressure by following the adiabatic cd 

 corresponding to the dry stage, but a dry stage with less quantity of 

 aqueous vapor than before. 



If we indicate by iV" the point at which this occurs or at which the 

 normal pressure is thus attained, then as the measure of the potential 



* lu the previous memoir, in consequence of an oversight, k was used instead of k 

 by von Bezold, but at his request this has been changed in the present translation. 



Fig. 36. 



