440 
ORGANISATION AND EMPLOYMENT OP SIEGE ARTILLERY. 
Normal 
energy 
necessary 
to pene¬ 
trate revet¬ 
ments p 
is therefore not to be sought in the use of less ammunition, but in other 
factors; these are, time and accuracy—a reduction of time required for 
breaching will always be important and necessary. The superiority of 
single shots will be especially valuable against bombproofs, covered 
from a high angle of descent, as under some circumstances, a single 
shot might suffice to penetrate and render them untenable at an early 
stage of the attack.” 
Further it may be stated, that a certain normal energy being 
necessary for penetration, this may be obtained more readily from a 
heavy than a light projectile, because a lower striking velocity will be 
needed by the former, to do the same work; in the case of high-angle 
fire, the required angle of descent can, therefore, be more easily obtained. 
No satisfactory experiments have been made in this country to 
determine the different resisting powers presented by walls of stone, 
masonry, or faced concrete; thus there are no data for estimating the 
normal energy necessary to any particular projectile, to penetrate 
various revetments. 
At the siege of Strasbourg, the gorge wall of Lunette 44, was 
destroyed from a distance of 960 yds.; angle of descent, 11° 45'; striking 
velocity, 475 f.s.; ordinary masonry; gun, 21 c.m. mortar (8*23-in. 
calibre). 
The normal velocity of impact would be 
475 x cos 11° — 45' = 475 x -93 = 465 f.s. 
Total normal energy 
o 
WO* 
176 X 465 3 
64*4 x 2240 
ft. tons = 
Normal energy per inch of shoFs circumference 
JE' 
7 r X 8*23 
In 1824 some experiments were made in breaching by curved fire, the 
ordnance used being 10-in. and 8-in. howitzers, and 68-pr. carronades; 
the elevations ranged between 13J° and 14°; the charges between 1 and 
2 lbs. A breach, 14 ft. wide, was made after an expenditure of 1400 
rounds; the striking velocities have been calculated at 253, 254, and 
284 f.s.; the energy would thus be. 40, 20*3, and 36*9 ft. tons. We 
see therefore, that very moderate velocities would give 40-pr. shells 
2 
sufficient energy (measuring by equality of — ) to breach ordinary 
1 2r/ 
revetments. For the 40-pr., 377, 269, and 362 f.s. would be equivalent 
velocities to those above-named. 
For the 12 and 15 c.m. guns, the Germans consider 220 and 160 metres 
the lowest limit of striking velocity for breaching*. 
In the case of using projectiles of different diametres, the necessary 
normal energy “ per inch of shoFs circumference” being known, the 
normal velocity could be calculated, and the requisite striking velocity 
for any angle of descent. 
