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MINUTES OF PROCEEDINGS OF 
from these causes affects very appreciably the flight of the projectiles / and 
as in the case of eccentric projectiles the direction of this rotation will vary 
according to the relative positions of the line joining the centre of figure and 
gravity, and the axis of the piece/ so also will the flight of the projectile vary 
from the same cause, and depend upon the angle which the line joining the 
centres of figure and gravity happens to make with the axis of the piece. 
But when an eccentric projectile is so placed in the bore that this line does 
not make an angle with the axis of the piece, but lies parallel to, or in, it, 
then no rotation will be generated, and no deflection from the natural line of 
flight be produced, except from those causes which produce rotation and deflec¬ 
tion in a concentric projectile, i.e., from windage, * 1 2 3 and an eccentric projectile 
thus situated may therefore be considered as a concentric projectile, being 
of figure. In this the impelling force passes through the centre of the ball, or nearly so, and acts in 
a direction parallel to the axis of the piece; but if the centre of gravity of the ball be out of the line 
of direction of the force of the powder, the shot will be urged to turn round its centre of gravity.” 
Treatise on Artillery, p. 158. 
1 “ A ball leaving the bore of a gun rotating on any axis, except one parallel to that of the bore, 
will deviate accordingly to the direction of the rotation.”— Motion of Projectiles, p. 26. 
“ If the anterior part of the shot turn from below to above there will be a force tending to raise 
the centre of gravity, and the range will be increased; if from above to below it will be diminished. 
Should the rotation be from left to right the shot will be thrown to the right.”— Treatise on Artillery, 
Section 1, Part I., p. 166. 
“ To our countryman Robins is due the credit of first pointing out the great change which the 
rotation of a shot would produce in the path of its flight.” — Ibid. p. 159. 
See Robin’s experiments and remarks upon this subject embodied in Ibid. p. 159-165. 
2 “ The direction of rotation will depend upon the position of the centre of figure with regard to 
that of gravity.”— Treatise on Artillery, Section 1, Part I., p. 159. 
“If a spherical eccentric projectile be placed in the gun; so that the line joining its centres of 
gravity and figure form an angle with the axis of the bore.the line representing the sum of all 
the forces resulting from the explosion of the charge, will not pass through the centre of gravity, as 
it passes through, or nearly so, the centre of figure; and the result will consequently be. a 
motion of rotation round an axis at right angles to the axis of the bore.”— RemarTcs on Diaphragm 
Shrapnel Shell, p. 18. 
“The shot.is found to deviate according to the position of the centre of gravity when the 
ball is placed in the bore of the gun.”— Motion of Projectiles, p. 26. 
3 “ The experiments in 1850 with shot purposely made eccentric and plaeed in the bore, with the 
centre of gravity in various positions.proved.that if the centre of gravity was placed in 
the centre of the piece, the eccentric lump being towards the charge, the range and deflection were 
about the same as those with concentric shells.” — Committee’s Memo, on Diaphragm Shrapnel 
Shell, p. 4. 
“ If the direction of the force be through the centre of gravity it causes a progressive motion only 
.If the body besides its progressive motion had a motion of rotation likewise, this last will not 
be changed by the action of a new force, whose direction passes through the centre of gravity.” 
Treatise on Artillery, Section 1, Part I., p. 157. 
In other words, if the force act through the centre of gravity, as it does in the case of a Spherical 
concentric projectile, and in the case of an eccentric projectile the line joining the centres of 
gravity and figure of which lies in, or parallel to, the axis of the piece, a progressive motion only, 
and no rotation, will be communicated to the projectile, —although such a projectile may have a 
motion of rotation from other causes, such as windage. Therefore, whether the projectile be con¬ 
centric or eccentric, so that it be situated with its centre of gravity in the axis of the piece, and 
with the line joining its tioo centres hi, or parallel to, that axis, it matters not,—the s/ime motion 
will be the result,, and the eccentric projectile under these circumstances becomes virtually, and for 
all practical purposes, a concentric one. 
