436 
ORGANISATION AND EMPLOYMENT OF SIEGE ARTILLERY. 
With each of the above units will be associated six 7-pr. R.M.L. guns 
of 200 lbs., on wrought-iron beds, carried in additional ammunition 
wagons and store wagons ; 300 24-pr. Hales' rockets with six troughs. 
Breaching. 
Breaching 
by canne¬ 
lure 
cutting. 
Until recently, the mode of forming a breach was to cut through by 
direct fire, that portion of the masonry required to be overthrown, and 
then either the weight of the superincumbent mass caused its fall into 
the ditch, or a few shots fired at low velocities, to shake and not 
penetrate, brought down the separated wall and rampart it supported. 
The method adopted was to cut the escarp first in a horizontal, and 
then in a vertical, direction. 
In general, the height of the horizontal cut was J that of the wall 
from the bottom, the length being regulated by the width of the passage 
required. 
The vertical cuttings were made from either end of the horizontal 
one upwards, and if the masonry was very cohesive, intermediate cuts 
were made as deemed necessary. The wall was divided into gun por¬ 
tions, and each piece completed its allotment. 
This plan necessitated an accurate knowledge of the profile of the 
works, the power of observing the striking of the shots, and great 
accuracy of fire—conditions which, in the days of S.B. ordnance, 
rendered it necessary to construct breaching batteries close to the 
fortress attacked. 
In 1870, some of the bastions at Strasbourg were breached in this 
way, at ranges of 790 and 875 yds., the greater accuracy of rifled guns 
enabling the cutting to be made at such distances. In old fortresses 
the revetments may still be thus destroyed, but in new works the 
cordon of the escarp is placed so far below the covering mass that a 
cutting, } the height up from the bottom, cannot be made by direct fire. 
Construe- In future therefore, breaches will have to be made by indirect or 
modern for- cury ed fire, unless it is possible to diminish the required angle of descent 
by cutting away the covering mass first. In some modern works, the 
profile is such as to necessitate an angle of descent, about 26°, in 
order to reach the middle of the escarp.* 
The necessity of using curved fire increases the difficulty of forming 
horizontal and vertical cuttings, for, not only is the fire less accurate 
(owing to the low velocity and longer time of flight), but the target 
becomes smaller as the angle of descent increases. 
Breachingby Breaching by curved fire, was successfully employed at the siege of 
m ^curved Strasbourg ; the right face of Lunette 53 was breached from a distance of 
about 870 yds., by oblique fire (55°), the angle of descent being 7° 45". 
After an expenditure of some 1000 rounds, from the 15c.m. gun, 
throwing a shell of 611bs., a passage was made 108 ft. long at top, 
and 90 ft. at level of standing masonry, the wall being 4J ft. thick at top, 
Necessary 
data for 
breaching 
by canne¬ 
lures. 
Example of 
cannelure 
breaching. 
necessitates 
curved 
fire for 
breaching. 
Greater 
difficulties 
of breach¬ 
ing with 
“ curved 
fire. 3 * 
or • 
fire 
* On account of the greater effect produced by elongated shells on bursting, half the height of the 
wall is now generally considered sufficiently low for the horizontal cutting. 
