THE ROYAL ARTILLERY INSTITUTION. 
233 
effect on the wall, being about one seventh (0*146) of the whole; out of the 
remaining 2945 rounds, 1000 took effect on the counterguard, and 608 on 
the rampart behind the wall; the breaching effect is entirely due to the 491 
rounds which struck the wall itself. Many shots were noted to pass a little 
to the right or left which would have struck a defence of less limited front¬ 
age, and have contributed to the result. 
One hundred rounds per piece, 1400 in all, made a practicable breach 
14ft. wide; 50 more rounds per piece, 2100 in all, made the breach com¬ 
plete in every respect. The rubbish was then cleared away both before and 
behind, when 85 rounds per howitzer, and 100 per carronade (1910 rounds) 
completed the demolition of the part which remained. 
5. Such then having been the effect produced by shot weighing 66*2 lbs., 
and shells weighing respectively 90 lbs. and 48*5 lbs., fired with low velocities, 
let us proceed to compare their effective powers with those of our existing 
rifled cannon projectiles. It is necessary for this purpose to ascertain their 
initial velocities, which has been done by Lieut. W. H. Noble, E.A., with 
Navez electro-ballistic apparatus, as follows :—- 
Table I. 
Nature. 
Length of 
bore and 
chamber. 
Calibre. 
Shot or 
shell. 
Charge. 
Initial 
velocity V. 
in. 
in. 
lbs. 
lbs. oz. 
ft. 
68-pr. carronade 
61-7 
8-05 
66-2 
1 O 
323 
10-in. howitzer... 
67-2 
10-00 
90*0 
1 3 
306 
8-in. howitzer... 
45*7 
8-00 
48-6 
0 11 
288 
The next table contains the value of Wv 3 for each of the above projectiles, 
and the velocity which will give the same value for the 40-pr., 70-pr., 7-in. 
howitzer or 110-pr. gun, and 7-in. mortar shells. Here v is the remaining 
velocity on impact. 
Table II. 
Nature. 
Smooth bores. 
Equivalent velocity for rifled 
common shells. 
W 
V 
Wv* 
a 
40-pr. 
70-pr. 
7-in. 
mortar. 
7-in. how¬ 
itzer or 
110-pr. gun 
lbs. 
ft. 
tons. 
ft. 
ft. 
ft. 
ft. 
68-pr. carronade. 
66-2 
284 
73-8 
362 
278 
246 
226 
10-in. howitzer... 
90-0 
253 
80-0 
377 
289 
256 
236 
8-in. howitzer... 
48-5 
245 
40-6 
269 
190 
182 
168 
6. We see at once that very moderate velocities will give 40-pr. common 
shells and still lower velocities give 70-pr. or 110-pr. common shells, breach¬ 
ing powers which measured by equality of Wv 2 shall be on a par with those 
