2lO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



At this moment the column is filled with air of the density p and 

 z = I and the motion is steady. Assuming approximately p' = p 

 we shall find 



P'o == P +gp' I 



and consequently 



P'o ~ Po = g I (P' - P) ■ ■ • ' ( 3 ) 



d z 

 Introducing w = , equation (2) will by integration give 



2=/(l-COSy/l (4) 



where 



J Po ~ Po /KN 



w = \j .... [ft) 



is the maximum velocity. 



The duration of the current up to the moment when the steady 

 motion commences, may be /„ and we shall have 



= ,.„ («) 







2 w 



Denoting by x and z f the mean temperatures of the column of the 

 current and of the column of the calm atmosphere, respectively, 

 we can assume approximately 



p' 273 + r 

 ~p = 273 + ? 



Equation (5) is now written in the form 



I gKr-t') 

 y 273 4- z' 



w 



Let 



/ = 1000 m , 

 r - r' - 6°, 

 273 +t / = 290°; 



we shall find 



w = 14.2 m and the duration t = 110 sec. 



