248 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



The absolute velocity U is found by the equations (i) and we 

 have 



U - Mr (7) 



U 



Assuming a — 45 ; -; = 1; k = 0.00006 we shall find for the 



asymptotes of the isobars 



y = 2.83 and y = - 0.478 



We easily construct the hyperbolas by the aid of the asymptotes 

 and of one point in the hyperbola. By introducing a mean value 

 of p and expressing the pressure in millimeters of mercury we shall 

 find by equation (4) 



for* = 0: f = 36.37 (b - b ) 



for y = 0: x 2 = 26.88 (b - b) 



By giving to the difference b — b the successive values i mm ; 

 2 mm. 3 mm ; etc., we shall locate the points by which we can con- 

 struct the hyperbolic isobars, as shown in fig. 54. 



To construct a trajectory of the wind we start from any point 

 whatever. 



