THE ROYAL ARTILLERY INSTITUTION. 
455 
CAUSES 
OS' THB 
DEVIATION OF PROJECTILES UNCONNECTED WITH RIFLING* 
BY 
LIEUT. W. E. RICHARDSON, R.E. 
All causes of the deviation of projectiles unconnected with rifling, are 
comprised under one or other of the three following heads :—» 
(1) Natural or physical causes ; 
(2) Causes arising from, defects of construction; 
(3) Accidental causes. 
Natural causes may again be subdivided into two classes:—- 
(a) Cosmical causes; 
( (3 ) Physical causes. 
Rotation of the Earth. 
The most important, and perhaps the most interesting of cosmical causes 
is the rotation of the earth, which has been often discussed by various authors, 
with whom I do not exactly agree in every particular. However, before I 
explain the difference in my views I will describe what occurs when a pro¬ 
jectile is fired in our hemisphere at a mark due north or south. 
Eig. 1. G is the position of a gun fired due south at a mark M. Now 
when the projectile leaves the gun G s it is impressed with a certain velocity 
west to east, which is the same by the second law of motion as that of the 
gun G. But the point M is rotating more rapidly than the point G, and 
consequently than the projectile, which will be carried to the right of M' , to 
the point P, where PM— GG'. A similar deviation to the right may also 
be proved when the shot is fired north, the deviation in each case varying as 
the range and the differential of the cosine of the latitude. South of the 
equator the same shot will deviate to the left. 
But there are an infinite number of complications attending the motion of 
a projectile when it is fired due east or west, or in a direction making an angle 
with the meridian. For if we examine Eig. 2, we see that gravity proper, 
and centrifugal force have a resultant which acts in the direction of the plumb 
* This paper originally appeared in the R.E. Professional Papers, hut has been re-written for the 
“ Proceedings.” 
[VOL. IV.] 
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