45§ SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5 1 



T 



ferences of log — - that is to say the difference between each two 



* 2 

 successive values. These differences are to be multiplied by the 

 corresponding values of m and the product is written in column 6. 

 For the initial condition / = 20 and p = -j6o mm we now compute 



log a - "; 



P'o 



The values of a = / (t) are to be taken from tables 5 and 6 and 

 placed in column 7 of table A. 



We distinguish between +o° C. as the final temperature of the 

 rain stage and — o° C. as the initial temperature of the snow stage 

 since the values of a are different for these two cases. 



If p = 760 and c m = i 7 mm , then p' = 743 mm . Since a = 

 137.6, therefore 



and again 



log p'o - -r = 2.6858 for t =20° 

 Po 



log p' - - = 2.6749 for t = 18 c 



This latter value is now the next initial value so that we obtain 

 the value for each successive 



a 

 log p' - ~, 



by subtracting 



m log — 



from the preceding value. But this is true only up to the temper- 

 ature o° C. or the end of the rain stage. With the temperature 

 o° C. we enter at once into the snow stage, that is to say, we com- 

 pute with the values a and m that correspond to the snow stage. 

 The final pressure of the rain stage as it is found from the equation 



40.0 

 log P' - —r = 2.5757 for + 0°C 



P 



viz: p' = 460 is the initial pressure of the snow stage. 



