OF SEVENTY-FIVE-MILE RANGE. 



■ 379 



The equations used are as follows 



(7) 



(9) 



(II) 



Ax 



(8) ^v, = -jvf{v)^^, 



gAx 



(lo) ^^ = - 



— AVr 



COS Or+l 



Vr+U 



(12) D, = 



The calculation is made as follows : An arbitrary value of x is 

 selected, the drop Ay is calculated from (7), the change in angle 

 from (10), the "set-back" from (12), and, finally, the corrected 

 value of y corresponding to the given x-Dj- is obtained. One row 

 of values is obtained for each element of the trajectory. 



Fig. 3 shows the details of the graphical method. After the 

 chords are drawn by means of a flexible ruler, the trajectory is 

 drawn through the vertices of the polygon constructed. 



In Fig. 4 are shown some of the most striking results. The 

 heavy black curve shows the surface of the earth and the change of 



