CAUSES OF DRIFT. 237 
feet to the second. At the present time our velocities are much higher, 
that is to say the resistance of the air is much greater, and the heads 
are struck with a radius of 2-in. diameter and the whole shell is longer. 
It seems to me that all these changes tend to increase the drift; but is 
this the case? Take a gun of moderate velocity, the 4°7-in. quick- 
firing gun, with a projectile of 45 lbs., muzzle velocity 1,786°8, I find 
that at 2,284 yards, the nearest range that I can get to compare with 
Table I., the drift was 7-2 yards right only ; the error in range 30°2 and 
the error in direction 0-4. Now let us take the most modern gun that 
we have, the 12-in. B.L., Mark VIII., shot 850 lbs., muzzle velocity 
2,360 feet to the second, head 2-in. diameter. With an elevation of 2°, 
range 3,451 yards, the mean deflection is 10 yards to the right only, and 
with an elevation of 9° anda range of 10,705 yards the deflection is 
20°6 to the right. It is therefore clear that the drift has diminished, 
not increased. Is this due to there being reduced time of flight? It 
can hardly be this altogether, because the 12-in. breech-loader at 10,000 
yards had hardly more drift than the 40-pr. breech-loader at 2,890 
yards. To my mind there is no doubt that the diminished drift is due 
to the greater steadiness of the projectiles of the present day ; they 
start without wobbling and they keep steadier to the end, having 
greater velocity of rotation. This 12-in. gun is perhaps the most 
accurate shooting gun in the world. At 7,082 yards the error in range 
is only 6:3, and the error in direction 1°6 ; at 10,000 yards it is only 14 
in range and 2°75 in direction ; and when fired at a target at 2,000 yards 
the only three rounds fired at the same elevation went through the same 
hole. With reference to the position of projectiles during flight, there 
can be no doubt that projectiles moving with a high velocity strike 
point first, but with projectiles moving with a low velocity and fired 
at high angles of elevation there is some diversity of opinion. To my 
eye one of these projectiles, when coming towards you, has in the 
descending branch of the trajectory its point very much to the right, 
looking as if it would fall sideways ; but as it nears the earth the point 
approaches nearer and nearer to the trajectory, and it strikes the ground 
point first. That it does strike the ground in this way is evident, as 
otherwise the direct action fuze would not act. From recent observa- 
tions carefully made on our practice grounds it appears that up to 60° 
they come down point first, but over that they cannot be depended on 
to do so. 
MAJOR P. A. MACMAHON, F.R.S., R.A.—Sir, I have been so long away 
from practical gunnery that it is with some hesitation that I respond to 
the invitation to take part in this discussion. There are many here 
who have had greater experience in observation of fire, and others who 
have made a special study of the theory, and I shall be glad to give way 
to them in a very few moments. 
It seems to me that General Owen has made outa very good case for 
Professor Magnus. So far as I can ascertain Professor Magnus’ theory 
has never been displaced ; I cannot find anything before us which can 
possibly take its place. Professor Magnus considers that the greater 
portion of the drift arises from causes which he specifies ; doubtless 
there are other causes of drift, but granting that the causes assigned by 
Professor Magnus are in some respects the chief ones, I think that 
Professor Magnus has made, many years ago now, the principal valuable 
contribution to the theory. He seems to have established that in the 
