THE DRIFT OF SERVICE PROJECTILES. 
465 
eventually get its point underneath, the trajectory. That is what actually 
happens and*'that is what would happen according to this theory, 
because with high elevations of 60° or 70° there is comparatively little 
curvature during the first third of the trajectory, say, and in the last 
third most of the curvature must be in the middle third or top of the 
trajectory. I think I am right in saying that in a high velocity gun 
the change of direction of the trajectory increases with the range and 
at the end of the range it is more than at the middle or the beginning. 
But with a low velocity gun, with high elevation, 60° or 70°, most 
of the curvature must be up at the top, so that the projectile 
when it gets up near the top will begin to feel the curvature of 
the trajectory. Up to this point it may keep its nose approxi¬ 
mately in the line of flight—forming its spiral, of course; after that it 
will have to try and get down to the trajectory and may not be 
able to succeed—it certainly will not as long as that curvature is 
changing as rapidly as it does. Some short time after passing the top 
will be the critical point; if it passes that point, from there to the 
bottom is pretty nearly straight and it could make up what lee-way it 
it has lost without the curvature bending much further away from it. 
What I hold then is that with a very high elevation the point must be 
on the right unless it has a very great deal of spin up to some way 
after the top of the trajectory and it is not till then that it can begin 
to catch up the trajectory again. 
It has been said that projectiles starting with very high eleva¬ 
tion, if they fall base first, drift a long way to the left, but I 
think in all these cases*the spin has lost command of the shot and it is 
not until it has turned broadside that it does show left drift. I do not 
attempt to explain this, but I think that anything after the shot has 
turned broadsidefis not of very much account. At the same time it 
may be on the same principle as in flying a kite with an insufficient 
tail, it sometimes makes a short dart to one side, stops, and then goes 
back wide on the other. I do not know whether that may explain it 
in any way, at any rate I do not consider it myself of much practical 
account. 
As regards the amount of divergence of the point of course it is 
very small, but I myself consider that the difference between the two 
divergences of the point to the right and to the left is sufficient to 
account for a good deal of drift. In left-handed rifling, of course, 
since the precession is in the same direction as the spin, the precession 
would be left-handed, instead of right-handed and the drift would be 
left-handed. Flat-headed shot I do not wish to touch upon, as the 
action of the air on its front end is not agreed upon. 
That, gentlemen, is all I have to say. I hope I have explained 
myself; but it is a most difficult subject to put into words (loud 
applause). 
