230 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5T 



The mean value of the thermometric gradient (see fig. 20) is 

 approximately: 



J = %P^ (4) 



2 r n 



and consequently 



W = 5.56 Hi °— li*. J (5) 



We have then in the examples following equation (6) of section 31 



W : J = 2 B. 



Third example. Let the isotherms be straight parallel lines. 

 Let us consider a cyclone and distinguish the interior region where 

 we have U = U i r and the exterior region where we have U r = m. 

 Substituting these values in equation (3) we shall find for the inte- 

 rior region 



r cos Up -f- <// — r) = = c 



1 0.0324 U x J 



which represents (see fig. 45) a straight line a b at the distance c 

 from the origin, and the angle between the axis X and the per- 

 pendicular c is (<p — y). 



fig. 45 



For the exterior region we shall find 

 0.0324 m J 



cos Up + (p - y) 



