238 CAUSES OF DRIFT. 
case of an ogival-headed projectile the drift is to the right, and in the 
case of a flat-headed projectile to the left ; and it immediately suggests 
itself to the mind whether there may not be some intermediate form, 
something between the ogival head and the flat head, for which there 
will be no drift. The drift to the right or to the left appears to arise 
from the fact that the direction of the resultant resistance of the air has 
a certain property with reference to the centre of gravity of the shot. 
It meets the curved surface of the shot and the direction of the normal 
to the surface at that point passes in the one case above the centre of 
gravity and in the other case below ; and, presumably, if the shot were 
to have a hemispherical head and the centre of gravity were to coincide 
with its centre this Magnus effect would in part disappear. 
This question seems to me to be merged in the very much larger 
question of the movement of the longer axis of the projectile. Drift is 
a very small portion of that question ; there are other points which are 
very interesting to artillerists which arise from the consideration of the 
accurate movement of the longer axis of the projectile. This movement 
of the longer axis is affected in a large measure by the elevation at 
which the shot is fired. That was shown very clearly recently at Lydd 
in high angle firing with low muzzle velocities, when at an angle of 
elevation of about 65° it seemed to be uncertain whether the projectile 
was coming down point first or base first. Surely it is a matter of very 
great importance to know how the projectile is coming down. Upon 
this depends the action, say, of a nose fuse ; if it comes down base first 
then the fuse is inoperative. It seems extraordinary that the facts 
connected with the movement of the axis of the shot should be so 
much in the form of conjecture. We hear that officers observe the shot 
when the shot is large and the velocity low ; they see the shot turn 
over or come down point first or base first, as the case may be. But 
surely anything that the eye can see a photographic plate can see better, 
and it seems extraordinary, considering the resources of modern 
photography, that so much should remain a matter of conjecture and 
should be dependent upon the very uncertain observations of spectators. 
(Hear, hear.) 
General Owen remarked in his lecture with regard to the drooping of 
the point of the shot that the holes made in certain vertical targets were 
circular. 
MAJOR-GENERAL OWEN—They were not vertical targets ; they were 
slightly inclined targets. : 
Major MACMAHON—I do not think that the angle at which a pro- 
jectile penetrates or commences to penetrate the plate ought to remain 
a matter of doubt. Professor Boys has shown a conical bullet in the 
act of passing through a glass plate ; he has made the projectile take its 
own photograph by setting off a spark from a Leyden jar. Some 
experiment of a similar kind would give very accurate information in 
regard to the exact angle that the projectile made with the plate at the 
instant that it commenced penetration. I feel certain that if the matter 
were put before an experimentalist like Professor Boys he would see 
no difficulty whatever, if the gun were a fairly accurate one and there 
were suitable conditions. I think, sir, it is very satisfactory that 
General Owen has re-awakened interest in this subject which has been 
dormant for so long, and I hope now that research will go on in order 
to find out accurately the movement of the longer axis of the projectile. 
