THE ROYAL ARTILLERY INSTITUTION. 
189 
Now, although it would be very difficult to ascertain exactly the point on 
the shot at which the resultant R may be said to press, it is evident that in 
all cases of practical gunnery this point will be below a , and, unless the centre 
of gravity of the shot is very near the point, in front of g } the centre of 
gravity.* * * § If the shot were fired without rotation it would turn over in flight, 
R causing the point to rise as indicated in Pig. 1. by the dotted shot ;t 
but if the shot be rotating rapidly while moving forwards at a high velocity, 
the point of the shot will not rise (at least perceptibly), but will move 
laterally to the right when the rotation is right-handed , and to the left when 
it is left-handed ; "consequently, the projectile assumes an oblique position 
to the direction of the air's resistance, and is thereby in its further progress 
depressed on the side towards which the apex is turned, while the air's 
resistance acts against it as against an inclined plane, and thus produces the 
deviation." { 
The direction of the graze of an elongated shot gives some indication of 
the turning of the point to the right. The grazes of the service shot fired on 
the 9th and 18th of April, as shown in the column of remarks in Tables V. 
and VI., were inclined to the right. In the artillery experiments made in 
Prussia at the suggestion of Professor Magnus, "it was also admitted by all, 
that, as much from the motion of the projectiles as from the furrows made in 
grazing the ground, in all the rounds fired, the point of the shot at the instant 
of touching the ground had a deviation to the right."§ 
The reason for the derivation of flat-headed projectiles fired with right- 
handed rotation being to the left instead of to the right will now be explained® 
In Pig. 2, P, G , and R as before represent respectively the force of pro¬ 
jection, that of gravity, and the resultant of the air's resistance. 
Eig. 2. 
If the shot (Pig. 2) were fired without rotation R would cause the head to 
turn down , as shown by the dotted shot, and not up as with the pointed 
shot; the flat-headed projectile would however turn over in flight, only in 
the opposite direction to that in which the pointed shot would turn. But 
if the fiat-headed shot have a right-handed rotation, R would cause the point 
* No shot have been used with the centre of gravity so far forward as to admit of the resultant 
acting behind the centre of gravity at ordinary elevations. 
f The turning over of elongated shot fired without rotation, and the experiments with the 
gyroscope are explained in Section II., chapter ii. of the “ Motion of Projectiles fired from Rifled 
Arms.” 
t Magnus on the Deviation of Projectiles, Berlin, 1860. Second Edition. 
§ Magnus on Deviation of Projectiles, “ Occasional Papers ” of R.A. Institution, Vol. I., p. 443. 
