224 . 
MINUTES OF PROCEEDINGS OF 
service mortar, a remarkable difference will be noticed. 5 lbs. with the 
latter is almost the exact equivalent to 60 lbs. with the former; but the 
tabular range for a 13-inch shell of about 204 lbs. weight due to 5 lbs. is 
only 1520 yds v , whereas 60 lbs. gave a mean range of 2300 yds. to two 
shells averaging in weight 2466 lbs. There is, however, no occasion to 
refer to the tables. Six 13-inch shells were actually fired for comparison, 
on the 18th December, 1857, with the following result:— 
Table VI. 
Comparative Practice with a \2>-inc7i Land Service Mortar of 36 act. 
Length of bore 2 ft. 8*5 ins. <\> = 45°. 
Rounds. 
Weight 
of shell. 
Charge. 
Observed 
range. 
t. 
Deviation. 
e 
lbs. 
oz. 
c 
p 
L. 
R. 
lbs. 
yds. 
secs. 
yds. 
yds. 
degs. 
1 
204 
5 
8 
•0247 
1846 
— 
57 
— 
57-9 
2 
206 
5 
O 
•0243 
1574 
18-0 
70 
— 
47-0 
3 
204 
5 
O 
•0245 
1610 
17-9 
10 
— 
48-9 
4 
204 
5 
0 
•0245 
1609 
_ 
— 
11 
59-9 
5 
203 
5 
0 
•0246 
1660 
18-8 
— 
40 
54-0 
6 
205 
5 
0 
•0244 
1537 
— 
2 
— 
50-0 
31. The velocity due to a 5 lb. charge is by calculation 428 ft. - * If we 
may place confidence in the mean of Professor Wheatstone's two results, 
the velocity given to a 36-inch shell of 2940 lbs. by a charge of 40 lbs. was 
408 ft.; and consequently the initial velocity of a mean shell of 2495 lbs. 
with 60 lbs. (Table IV., rounds 6 and 17), which bears the same proportion 
to it as 5 lbs. to 204 lbs., would be 547 ft. This immense excess of initial 
velocity in the larger shell for the same proportionate charge, fully accounts 
for its greater range. It is the velocity due to a charge of 8T81bs. in the 
13-inch, for which the tabular range is 2600 yds., and may doubtless be 
attributed to the following causes :— 
(a) Windage of the 36-inch shell, in relation to the sectional area of 
the bore, less than that of the 13-inch shell in the proportion of *01 to ’03. 
(b) Partial stoppage even of this reduced windage, by the use of sawdust 
in the chamber. 
(c) More complete combustion of the powder. 
(d) A smaller relative resistance from the air. 
Comparing the observed time of flight of the 13-inch shell with the time 
due to the same range in vacuo, it is greater whichever equation we employ. 
tan 0 
2 9 
secs. 
= 17-35 
C cos <fr 
= 16-02 
a) 
(2) 
* Sefe W. H. Noble, 2nd Report on Ballistics, p. 18, for the data; 
