MINtTTES OF PROCEEDINGS OF 
492 
in the same direction. But if yon could watch more closely, you would 
see that it is the side of the groove which is opposite to the direction of 
revolution which drives the stud round, just as the left rail, in the illus¬ 
tration I have taken, drives the train to the right, where the line of rails 
curves in that direction. We see, then, that one side of the groove 
does all the work in driving the shell round. Now, if that side 
were perpendicular to the bottom of the groove, it is true it would 
drive the shell round; but as the studs to enter the grooves must 
have some play—that is, the diameter over the studs must be less 
than the diameter over the grooves—there is no reason whatever 
why the shell should not be hard jammed towards one stud, the 
whole of the play being over the others. Instead, however, of the 
driving side being perpendicular to the bottom of the groove, if we 
make it oblique to the radius, and if we make the driven edge of the 
stud to conform to it, the rotation of the shell, or rather the force which 
causes it to rotate, will compel the studs to ascend the inclined planes 
of the driving sides of the grooves until the shell is firmly centred. If 
we could only centre the shell after loading and before firing—that is to 
say, bring all the driven sides of the studs against the inclined driving 
planes of the grooves, there would be much less damage done to the 
first foot or so of the grooves than actually takes place. For observe, 
on this system, when the shell is loaded, it is loose in the bore and 
grooves; but when the powder explodes behind it, the shell is sent 
forwards by a tremendous force impelling the studs against the driving 
sides of the grooves. This causes considerable wear for some short 
distance in front of the shell; but as there are some three or four feet of 
grooving uninjured in this way, the shooting is unimpaired for a great 
number of rounds. 
In the Austrian system,* which is in principle precisely like that I 
have described, the whole of the groove is a curved inclined plane ; and 
by way of locking them into a centrical position, the shells have warts 
or drifts at the nose which fit into a bayonet-joint on the sheet-iron 
flange of the rammer-head. As soon as the shell is set home on the 
powder, the loadsman turns the staff of the rammer to the right, and 
thus centres the projectile. 
I am by Do means satisfied that this centering before firing could not 
be managed with our muzzle-loading shells. But the endurance of the 
guns is already so great, that it seems hardly necessary to complicate 
the loading with even this trifling addition. The truth is that, thanks 
to the admirable workmanship in the Royal Arsenal, the shells are now 
made with a clearance between the sides of the studs and the grooves of 
only T Joth of an inch; thus the driven side of the stud must be brought 
in contact with the driving side of the groove almost instantaneously. 
18. Let me now give you a few details of the bronze muzzle-loading 
field 9-pr. gun adopted for India. 
The gun weighs about 8|- cwt.f Its length of bore is 68*5 inches, 
its calibre 3"; its breech preponderance is about 8 lbs. The rifling is 
* Vide Fig. 4. 
f Vide Fig. 5; 
