THE KOYAL AETILLERY INSTITUTION. 
165 
the time obtained 0"*107108, the velocity of the projectile 
distant point is 
120 
0107108 
1120-4 feet, 
% 
at the equi- 
and as the first target was at a distance of 30 ft. from the muzzle of the gun, 
1120*4 is the value of v at 90 ft. from the muzzle.* This velocity must be 
corrected to that which it would have been at the muzzle. 
30. The initial velocity of a projectile has been calculated from several 
different formulm. The one which has been used in the experiments with 
Navez's electro-ballistic apparatus at Shoeburyness is 
1+L v = { l + j) 
in which x is the distance from the muzzle of the gun to where the velocity 
is v. The value of r is constant and equals 1427 ft., and the ballistic 
coefficient c is given in the following tables for all descriptions of 
ordnance. 
This coefficient is calculated according to Didion's law of resistance, 
which, as before stated, is open to correction. However, within short 
distances it may be assumed as practically correct. 
I. 
Table giving the value of the Ballistic coefficient C for English projectiles . 
SMOOTH BORES. 
Ordnance. 
Projectile. 
Nature. 
Mean weight 
including bursting 
charge, fuze, &c. 
Mean 
diameter. 
Value 
of O 
in feet. 
Remarks. 
68-pr. 
32-pr. 
24-pr. 
18-pr. 
12-pr. 
9-pr. 
6-pr. 
10-in. \ 
68-pr. ...J 
8-in. 
32-pr. 
24-pr. ... 1 
6*-in.5 
18-pr. 
12-pr. ...} 
4f-in.) 
32-pr. 
24-pr. 
18-pr. 
12-pr. 
9-pr. 
6-pr. 
Shot 
Com. shell 
Diaphragm 
shell 
lbs. 
66-520 
31-375 
23- 500 
17-687 
12- 625 
9-370 
6-245 
92-625 
49-875 
24- 312 
17-500 
13- 125 
9-000 
60-750 
28-750 
20-875 
15-875 
10-375 
8-060 
6-125 
7-91 
6- 17 
5-60 
5- 09 
4-52 
4- 10 
3- 57 
9-84 
7 - 86 
6- 17 
5- 59 
5- 09 
4- 45 
7- 91 
6- 17 
5- 59 
6- 09 
4-45 
4-08 
3-56 
5870-0 
4569-0 
4154-3 
3784-6 
3425-7 
3090*1 
2716-4 
5303-2 
4475-5 
3540-4 
3099-1 
2808-4 
2515-0 
5382-6 
4186-6 
3696-8 
3396-8 
2898-6 
2684-2 
2241-8 
The values of C have been 
calculated from the formula 
' 1 P 
g = 32-1908 ft., 
A = 0-0005137, 
3-1415926, 
2R = diameter of shot, 
P = weight of shot. 
If projectiles differ much 
in weight from the weights 
given in the Tables, it will 
be sufficient to multiply G 
by the ratio of the weights. 
P' 
C'= C-S' 
If the diameter differs in 
the inverse ratio of the 
squares, 
R2 
c '=°iF- 
* This is not mathematically correct, but the error is so very minute that practically the computed 
velocity may be assumed to be that at the middle of the distance between the two targets. 
