THE ROYAL ARTILLERY INSTITUTION. 
231 
ON THE APPLICATION OP RIFLED CANNON TO THE OPERATION OF 
BREACHING UNSEEN DEFENCES 
BY HIGH ANGLE FIRING. 
By Colonel LEEROY, R.A., E.R.S. 
1. The present notes have reference to a question which arose on one 
of the preceding papers, when it was read a few weeks since at this 
Institution, and which was expressed in the following terms. “ What is the 
greatest amount of curve that can be given to the Armstrong projectile, still 
preserving its power of penetration, and limited to what range?” The 
question had reference to the practicability of breaching masonry concealed 
by earthwork in front of it: as for example in firing over the crest of a 
glacis against an escarp unseen; and it is evident that in replying to it we 
must take the case of some particular projectile, and assume some definite 
resistance. Eor reasons which will presently appear, the 12-pr. and 20-pr. 
guns may be at once given up, as too light for the task. I shall assume 
therefore that the battering gun is not less in calibre than a 40-pr., and 
the escarp built of good brickwork. 
2. In this form the question is. What are the smallest 40-pr. charges 
which will secure a serviceable degree of penetrating power at given distances ? 
To have a considerable descending angle we must have high angles of eleva¬ 
tion. To combine high angles of elevation with a limited range we must 
use a small charge; the smaller the charge that will do the work, the lower 
in vertical descent may we go, and the greater the choice of position for the 
battery. The famous experiments made in this garrison by order of the 
Duke of Wellington, in 1822 and 1824, furnish the first and most obvious 
standard of comparison. 
The experimental practice of 1822, it will be remembered, was at a screen, 
and chiefly intended to furnish data for an actual operation of breaching. 
I extract an account of it from a manuscript in my possession in the hand¬ 
writing of the late Sir Alexander Dickson, a name never to be mentioned by 
the Artilleryman without honour. It seems to be the draught of a report, but 
whether of a report actually rendered does not appear. Referring the reader 
to the Appendix (p. 239) for this document, it will be sufficient to say that it 
concludes by stating that the 10-in. howitzer, 8-in. howitzer, and 68-pr. 
carronade had proved themselves the most efficient pieces for this description 
of fire, and by recommending further experiments with them against an 
actual Carnot's wall. The angle of elevation was to be 15°, and the charges 
adjusted accordingly; however, as we shall see presently, it was not actually 
so great. The wall was erected in the summer of 1823. It was 21 ft. high, 
7 ft. thick at the bottom, and 6 ft. thick at the top, with a frontage of 30 ft., 
[vol. in.] o 
