THE ROYAL ARTILLERY INSTITUTION. 
187 
and be of precisely tbe same weight. One shot should be fired with a 
velocity 1200 f.s., then one with 1150 f.s., then one 1100 f.s., so far as the 
height of the screens would allow. The same series must be gone through 
three times more. In the subsequent treatment of a complete and 
standard experiment of this kind, it is evident that instead of measuring 
the time from the instant of passage of the first screen, it will be necessary 
to measure the time in each round of four, from the instant when each 
shot had a certain velocity. 
A few hollow shot of the same external form might be fired with advan¬ 
tage. Tor low velocities it would be advisable to remove three or four of 
the middle screens. 
A good test of the truth of the law deduced from experiments with 
various initial velocities would be obtained by firing a few rounds with the 
highest initial velocity through three screens near the gun, and three at a 
distance of 4500 or 6000 feet. The chronograph would give initial and 
final velocities and the time of flight. It would be advisable to try the 
experiments on the long range when the wind was blowing directly 
with and directly against the shot, also when the wind was blowing at 
right angles to the direction of the line of fire. Also the effect of the 
height of the barometer, and of the degree of moisture, on the resistance of the 
air might best be determined by a few shots on the long range when the air 
was perfectly still. 
In the experiments just suggested, the law of initial velocity, so far as it 
depends upon the charge, would be determined with great precision. The 
results might also be treated in two ways, that is, so as to obtain both an 
average velocity at any distance from the gun, and the true law of the 
resistance of the air. 
If similar forms of shot were used in experiments of the above kind, 
with bores of 3, 5, 7, 9, 11, and 13 inches, we should be able to extend, by 
interpolation, the laws obtained from these experiments for the above 
particular cases to all possible calibres from 3 to 13 inches. It would be an 
easy matter to bring all needful experiments of the above nature to a 
satisfactory conclusion within six months. When this work was once well 
done there could be no pretence for ever re-opening the question. Take, 
for instance, the table of velocities which has been given for one particular 
calibre and form of head. What more information can be required for the 
same gun and projectile after that table has been extended both ways with 
the same exactness, to the highest and lowest practical limits ? The force 
of the charge of powder, taking account of quality and quantity, must be 
known in any practical case. Suppose that the initial velocity for a smaller 
charge, or a different powder, was 1120 f.s., and that it was required to find 
the velocity at a point 500 feet from the gun. Referring to the table, we 
find the velocity at 394 feet from the gun was 1120 f.s., and 500 feet 
farther on, or at 394 + 500 = 894 feet in the table, the velocity was 1071 
f.s. So that a shot starting with an initial velocity of 1120 f.s. would have 
a velocity 1071 f.s. after it had travelled 500 feet through the air. All this 
information is derived purely from experiment, and is therefore free from any 
question as to the value of a formula or a theory. Tor a hollow shot, of 
the same external form as the solid shot used in the experiment, the air 
would exert precisely the same resistance for a given velocity; but its effect 
