190 
BURSTING OF HEAVY GUNS. 
with Woolwich gas-check, but without studs, in order to enable it to 
go home past the termination of the rifling. Over these was rammed 
home a charge of 10 lbs. 10 ozs., and a 75-lb. cast-iron shot with gas- 
check and studs. No very marked result was produced on firing. 
The gun ran up its rails fairly, and the bore was measured as 
registered in parallel space marked No. 1 round in Fig. 1. 
Round 2 .—The gun was loaded in succession with 16 lbs. of powder, 
a 100-lb. cast-iron shot, without studs but with a gas-check, 11 lbs. of 
powder, and an 85-lb. shot, with studs and gas-check, and fired. The 
measurements taken afterwards are registered in the space marked for 
No. 2 round. 
Round 3 .-—The gun was loaded successively with 18 lbs. of powder, 
100-lb. shot, 12 lbs. of powder, and an 85-lb. shot, and fired. For this, 
and with successive rounds, all shot had gas-checks and studs. The 
recoil was now very violent. A larger number of bore measure¬ 
ments were taken, as shown in the space between parallel lines, 
“No. 3 round/*’ Fig. 1. 
Round 4 .—The gun was loaded with 20 lbs. of powder, a 100-lb. 
shot, 13 lbs. of powder, and an 85-lb. shot, and fired, the expansion 
being registered in the space between parallel lines marked “No. 4.” 
(Pig. i). 
Round 5 .—The piece was loaded with 22 lbs. of powder, a 100-lb. 
shot, 14 lbs. of powder, and an 85-lb. shot, and fired. The splinter- 
proof roof fell in over and round the gun, which did not appear out¬ 
wardly to be injured, but it was impossible to obtain exact results for 
a considerable time. These results, however, which are not shown on 
the cuts herewith, were very similar to those obtained in the previous 
rounds. 
There can be no question that the gun stood admirably. I believe 
that permission was given by the War Office to fire the service 
7-in. gun with 30 lbs. of pebble powder and a 160-lb. shot. In actual 
amount the fourth round consisted of 33 lbs. of powder and 185 lbs. of 
shot, but the great strain is of course due to the distribution of the 
charges and shot. 
As concerns the local action of the pressures on the bore, taking 
the registered expansions as far as we have them, we may observe 
a little inaccuracy in measurement, but this must inevitably occur. 
For example, the bore at 7 ft. depth increases up to an extent 
of *008 in. at the third round, and drops again at the fourth. The 
bore cannot be measured in precisely the same spot each time, and 
expansion need not be perfectly concentric and symmetrical. It will 
be seen that the measures consistently show a maximum permanent 
expansion opposite the front portion of the front cartridge. 
It may require explanation how it is possible for this gun to have 
stood the tests imposed on it at all. First, then, it must be remem¬ 
bered that coil tubes entered into a cast-iron gun by the muzzle must, 
of necessity, be as thick, and therefore as strong, at the muzzle end 
as at the breech end of the bore. Such tubes being strong enough 
for the work falling on them at the breech, must have a great margin 
