158 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5 1 



The hypothesis that the pressure diminishes with the distance 

 from the center requires that 



v < 



cos a 



In nature the wind about barometric maxima always has a slight 

 velocity and the pressure diminishes with distance from the center, 

 However, we can apply the formulae only to the exterior parts of 

 the whirlwind, because in the interior part the currents are not 

 horizontal, but have a vertical descending velocity which influences 

 the horizontal movement. 



Applications 



Whirlwind about a barometric maximum (see fig. u). 

 Let the latitude = 45°, 



k = 0.00012, 

 M 



- 0.0009281 (t = 0°, b = 760 tni »), v = 4 m , r = 5 C 

 P 



we find 



3.406 3.879 

 a =40° 35'. 9; G = - - - —j- 



r 1.94 r. 



b - h = 7.841 log - - 0.0776 + — 1~; ? = 113 log.- 



r Q r r 



§14. Currents of air in the interior part of an atmospheric whirl 



In § 12 and § 13 we have considered currents of air flowing at a 

 constant elevation approaching the center of the isobars or moving 

 away from it. In nature the elevation of the currents does not re- 

 main invariable; in atmospheric whirls around a barometric mini- 

 mum the currents have an ascending movement that increases 

 toward the center, and in whirls about a barometric maximum the 

 currents have a descending movement that diminishes with the 

 distance from the center. We shall treat the general problem in 

 the second part of these studies, but at present we will consider a 



