460 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 51 



ference is only 1.5. If a hail stage occurs then, for p' = 458 and 

 £ = 14 grams we obtain 



45.2 , 40.0 



log P' -~Y= log p - ~, 



1.82 £ = 2.5486 



whence we find p' = 447 mm or an isothermal diminution of pressure 

 of n mm and the final p = 452 mm . 



With p' = 447 mm as the initial pressure of the snow stage and 

 m IV = 3.54 there results for the final temperature — 18 C. and 



11.7 , 45.2 T 



log p' - —7 = log p ~ —, - m log — = 2.4434 ' 

 p pi 



In this case we find p' = 303 and p = 304. 



The final results for the adiabat as Compared with those for the 

 pseudo-adiabat are given in the following table: 



TabU B 



The values of the pressure for the pseudo-adiabat are always 

 higher than those for the adiabat for the same temperatures. If 

 we ignore the isothermal diminution of pressure during the hail 

 stage, which only occurs in special cases, then the departure at the 

 end is only 1 millimeter and is therefore so slight that it can come 

 into consideration only in very rigorous investigations. In the 

 computation of changes of condition of ascending currents of air it is 

 practically almost indifferent whether we compute by the adiabat 

 or pseudo-adiabat formula, that is to say, whether we assume that 

 the condensed water remains suspended in the air or falls away as 

 precipitation. The only characteristic difference is the omission of 

 the isotherm of the hail stage in the pseud o-adiabatic changes of 

 condition. 



Since in the actual atmospheric processes neither one nor the 

 other boundary limit is strictly fulfilled and it is therefore almost 

 indifferent which of the two isotherms we take in the computation of 



