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WEBSTER— BALLISTICS OF A GUN 



range, amounting to about a mile, that it would cause (neglecting 

 the conversions of the verticals). 



The method of choosing was frankly one of guessing. At first, 

 an angle of departure of 45° was assumed with an initial velocity 

 of 1,300 meters/sec. This gave Curve i. The angle of departure 

 was then increased to 52°, which gave Curve 2, with a range of 120 

 kilometers. In order to show the enormous effect of the resistance 



1 e.= 4S° ff= cSi^ifM 

 z e.--5z' ft= CJty)fW 



f e.-45' R-o 



3 Surface of Earih 

 X 



Fig. 4. 



100 Kilometers 



of the air. No. 4 is drawn showing the parabolic or vacuum trajec- 

 tory, with a range of 174.4, and, finally, No. 3, on the assumption 

 that the air has the constant density found at the surface of the 

 earth. Further, the trajectory that we should have in case the den- 

 sity had the constant value, taken at a height two thirds of the 

 maximum, as suggested by Colonel Ingalls for shots nearer the sur- 

 face of the earth, was calculated. The range obtained was ap- 

 proximately 56 kilometers, quite different from the correct value of 

 Curve I. 



Note, May 2, 1919. — The foregoing paper, which was read over 

 a year ago, has, of course, lost the timeliness that it had at that mo- 

 ment. In fact, I have been advised by a high ballistic authority not 

 to publish it, as such calculations are now " a matter of routine." 



