236 CAUSES OF DRIFT. 
rotating round its shorter axis.” Some fell flat cn the ground and 
others struck on their shoulders with points slightly upwards to the 
left, or in other eccentric positions, so it is evident that with this charge 
the velocity of rotation was not sufficient to keep the shells even point 
first during flight, and those with percussion fuses would consequently 
be blind. 
The muzzle velocities given to the 6-in. Howitzer shells with charges 
of cordite powder would have been about— 
12 0728. ... ae ike ... 447 feet. 
1B. op , aoe ah 465 ,, 
SPA ep obo aie cco FOB. op 
Those of the 9-in. Palliser shot and cast-steel shell, with 183 lbs. 
charge of ordinary powder, were 568 and 611 feet respectively. The 
records of the velocities for the 124 lbs. and 74 lbs. charges are uncertain, 
the velocities not being high enough to break the wires properly. 
Although the velocities must be low with the 74 lbs. charge, a number 
of shells having gas checks, fired at 20°, 30°, 40°, 50° and 60°, had all 
right deflections; in this case the velocity of rotation being low the 
resistance tending to upset the shot would be comparatively slight. 
The left drift of certain shells at very high angles (those of 6-in. 
Howitzer and a few of the 9-in.) is probably caused by the resultant of 
the air’s resistance acting below the centre of gravity of the shell in 
these cases ; but as these shells were unsteady in the descending branch 
of the trajectory and turned over in various eccentric ways, it is clear 
that the velocity of rotation became too low to keep them point first. 
Lieut.-Colonel Bally informed me that, as a rule, if the shell falls base 
first the drift is to the left. This is a curious fact, but the falling base 
first is probably due to the circumstance that the base end of the shell 
is heavier than the head, and that it tends to drop after the velocity of 
rotation has ceased to keep the shell rotating steadily round its longer 
axis. Iam also informed that along shell will fall base first when a 
shorter Palliser shell, fired with a similar charge and at the same angle 
of elevation, will fall point first. Of course, the longer the projectile 
the higher is the velocity of rotation required to keep it point first. 
It may be seen from the tables that the drifts at these very high 
angles did not increase in the high proportion, compared with the times 
of flight, that they did at the angles from 4° 20’ to 35°, with the 8-in. 
Howitzer given me by Major-General Nicholson. 
One of my old brother officers, when holding a scientific appointment, 
wrote to me, saying : “ That the question, I have endeavoured to explain, 
is a matter of no practical interest.” I venture, however, to think that 
those, either of the military or naval services, who look upon gunnery 
as a science, and not a mere rude art to be practiced by “rule of thumb,” 
will not consider the discussion of such questions a waste of time. 
DISCUSSION. 
THE CHAIRMAN—I think it might be interesting, gentlemen, if 1 
supplement the results which the lecturer has given us by giving you 
a few of those obtained with very modern artillery up to date. I find, 
so far as I can make out with reference to Table I., that in 1861 with a 
40-pr. R.B.L. gun the shot had a radius of head of about 1}-in. diameter 
and was about 24-in. calibre long, and the muzzle velocity was about 1,180 
