246 VELOCITY OF EFFLUX OF AIR. 



COB. 1. If the pressures p l and p z are nearly equal to 

 each other, we can put 



which in (7) gives 



- (8) 



When T is very small (8) becomes 



v = 1299 4(l + at) . (9) 



COB. 2. Taking </ = 32, we have from (1) 



v = 8\ /^ilog^i. ' (10) 



V W ^2 



When the pressures differ but little from each other, we 

 may obtain approximate formulae as follows : From (10), 

 we have 



Mogi. (11) 



W J9-, 



By development we have 



Neglecting all powers of ^1 above the first, and sub- 



Pi 

 stituting in (11), we have 



