386 
PEOPOSED EUSSIAN FIELD GUN. 
70 calibres was found most suitable. The following were the results 
obtained:—■ 
Distance. 
Angle of 
elevation. 
Angle of 
incidence. 
Mean quadratic 
deviation. 
Vertical. 
Lateral. 
sagenes. 
yds. 
O / 
° / 
yds. 
yds. 
600 
1167 
1 36 
2 3 
0-93 
;1*07 
1000 
2333 
4 18 
6 12 
3-06 
3-03 
1500 
3500 
8 7 
12 26 
7-85 
6’50 
These results prove that the accuracy of the hooped steel 4-pr. is 
very closely the same as that of the bronze gun firing at an initial 
velocity of 1340 ft. per second, and that the tension of the trajectory 
is from 20 per Gent, to 40 per cent, greater than that of the 9-pr. 
service gun. 
The cause of there being no increase of accuracy, despite the increase 
of initial velocity from 1340 to'1703 ft. per second, is due probably to 
the injury suffered by the lead-coating of the projectile from the high 
velocity. It would appear that what ought to have been gained in 
accuracy through increase of velocity was lost by the perturbation of 
the motion of the projectile as it passed along the bore of the gun, due 
to the damage done to the lead-coating. 
The better to appreciate the influence of the tension of the trajectory 
and of the accuracy of fire on the probability of a hit with the heavy 
steel 4-pr. as compared with the service 4 and 9-prs., let us calculate 
the probabilities in firing at low angles, both when the distance is 
accurately known and when an error is made in estimating it. The 
result of these calculations is contained in the following table :— 
Number of Hits per cent, on a Target 6 ft. x 58 ft. 
Firing at distances 
accurately known. 
Firing at distances wrongly 
estimated 
Distance. 
by 2 per cent. 
by 5 per cent. 
Heavy 
4-pr. 
Service 
9-pr. 
Heavy 
4-pr. 
Service 
9-pr. 
Heavy 
4-pr. 
Service 
9-pr. 
sagenes. 
300 
yds. 
700 
95 
95 
92 
86 
73 
37 
400 
933 
82 
82 
1 72 
58 
33 
1 
500 
1167 
68 
67 
52 
34 
11 
1 
600 
1400 
56 
53 
36 
20 
8 
— 
700 
1633 
46 
41 
25 
13 
— 
— 
800 
1867 
38 
31 
17 
9 
— 
— 
As will be seen from this table, there is no substantial difference 
between the two guns thus compared, so long as the distances are 
