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XV. On the Law of the Resistance of the Air to Rifled Projectiles. 
By Charles W. Merrifield, F.R.S., Principal of the Royal School of Naval Architecture. 
Received March 1 9, — Read April 23, 1868. 
At the beginning of this month Lieut.-Colonel H. B. Halford applied to me to obtain 
for him the law of atmospheric resistance resulting from his experiments in shooting 
with Metford’s match-rifle, a small-bore with increasing pitch. I found the resistance 
to vary as the cube of the velocity. 
As the calculations and experiments were all made without any notion of the resulting 
law, and without any knowledge of the work already done by Professor Helie and Pro- 
fessor Bashforth, they afltord a remarkable confirmation of the results obtained by those 
gentlemen. This is the more worthy of notice, as their data belong to pieces of large 
calibre, and mine to small-bore bullets. 
The experimental data originally submitted to me were simply the elevations found 
necessary to give the different ranges of every 100 yards from 100 to 1100. These were 
as follows : — 
Yards range. 
Elevation. 
100 
9 30 
200 
20 — 
300 
31 30 
400 
44 — 
500 
57 30 
600 
1 12 — 
700 
1 27 30 
800 
1 44 — 
900 
2 1 30 
1000 
2 20 — 
1100 
2 39 30 
I was informed that these were the means 
derived from a g 
trials, bad shots being of course discarded. 
The laws of the motion were arrived at tentatively. I began the calculations from an 
assumed velocity of 1360 feet per second, which is seen by the shorter ranges to be very 
nearly true, of necessity. I then found that the law of the squares did not fit the results 
at all, but that the law of the cubes very nearly did so, and a slight alteration in the 
assumed velocity made them do so with exactness. 
The method used was to determine the coefficient of resistance m , in —mv 3 , which 
mdccclxviii. 3 Q 
