THE ROYAL ARTILLERY INSTITUTION. 
347 
scale an inclination to the left equal in angular value to -^th the angle of 
elevation, they have consequently no deflection scale; but for the same 
reason, no means of applying an accurate correction for the variable effect of 
wind. The amount of the correction is due to the fact which has been 
observed that the derivation at any distance is one-tenth of the quantity by 
w r hich the trajectory deviates from the prolongation of the axis of the piece, 
ligne de tir in French terminology, but for which we have no convenient 
term in English. 
For 600 m. it is given as 1 m. 1 For 2000 m. it is given as 25 m. 
1000 m. „ „ 6 w I 3000 m. „ „ 80 » 
6. The initial velocity of the shell is about 1066 ft. (325 m.) per second 
for the service charge of 0*55 k and the remaining velocities are nearly as 
follows:— 
Tangent 
scale. 
Eleva¬ 
tion. 
Remaining 
velocity. 
mm. 
o / 
ft. 
At 500 metres or 647 yds. 
14-0 
1 10 
032 
1000 „ „ 1094 „ 
84-5 
2 60 
817 
1600 „ „ 1640 „ 
61-2 
5 5 
722 
2000 „ „ 2187 „ 
94*2 
7 45 
650 
A comparison of these elevations with those which the Armstrong 12-pr. 
requires for the same ranges, viz. O' 37", 2° 16', 4° O', and 5° 49' or there¬ 
abouts, shews a much more highly curved trajectory, which is so far a 
disadvantage. It has in fact been ascertained by measurement that the 
highest point of the curve of the 12-pr. on a range of 1000 yds. does not 
exceed 33 ft.; that of the French projectiles for the same distance is 38 ft. 
7. The penetration of the shell of 4 Jcilos. with the service charge is 
stated to be as follows:— 
Into brick at 71 yds., a wall of 47*2 inches thick. Penetrated it. 
Into good masonry at 76 yds. 23-6 in. 
Into oak 41*2 inches thick at 437 yds. 32*7 n 
Into earth at 3500 yds.. 67.0 « 
The Armstrong 12-pr. segment shell has been fired at the same distances 
into very solid brickwork, namely, that of a Martello Tower 56 years old, 
and into a cubical mass of the soundest oak, giving respectively 21*2 in. and 
27*2 in. of mean penetration. It is however necessary that guns should 
be fired into the same object if we wish to compare penetrations exactly: 
a shot will go through a 4 ft. wall by being enabled to knock out the 
bricks behind, when it will not penetrate nearly four feet into a 7 ft. wall. 
It may, however, be conceded that the strength of the French common 
shell adapts it better to penetrate hard substances than does the construction 
of the 12-pr. segment shell: no observations have been made of the 
penetration of the 12-pr. common shell, which is not generally introduced. 
