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MINUTES OE PllOCEEDINGS OF 
4. But the metal of the gun has more to stand than the mere friction 
of the studs of the projectile ; it has first to sustain the expansive force., 
and second , the great heat of the powder gas. 
Now, as to the first point—the expansive force—I believe there is no 
known metal or combination of metals which gives such absolute 
security from bursting as bronze. It is not that an individual steel gun, 
with or without wrought-iron coils, may not be stronger perhaps than 
an individual bronze gun of the same size; but take 1000 bronze guns, 
and you may be perfectly certain that not one will burst. It remains 
to be seen if the same is the case with steel guns, with or without 
wrought-iron coils. 
The Prussian Ordnance Committee made some interesting experiments 
on the resistance of bronze. The guns used were the 4-pr. and 6-pr. 
The former fires a shell of about 9 lbs. weight, while the gun weighs 
about 6cwt., and the latter a shell of about 15 lbs., with a weight of 
gun of 9 cwt. 
I will confine myself to the former. They turned down the gun of 
6 cwt., a small quantity at a time, until it weighed only 2 cwt., the 
thickness at the breech being reduced from 2*4" to 0*8 ", and at the 
muzzle from 1" to With this gun they made a series of experi¬ 
ments, firing a 9 lb. shell with a charge a little over 1 lb. After each 
series, the bore was examined to find out where expansion first took 
place. It was only after the thickness at the seat of the charge had 
been reduced below 1J inches that expansion took place. Further, with 
this thickness, expansion took place after a few rounds and then ceased. 
When the gun was reduced to a thickness of under a J of an inch, 
small cracks were observed through which the powder gas escaped ; 
the gun was, however, fired with safety. 
The heavier gun of 9 cwt., with a shell of 15 lbs. and a charge of 2^-lbs., 
when reduced to x Vfchs inch thickness at the muzzle, burst, throwing a 
good large piece out of the chase with violence. Thus there was ample 
indication of approaching rupture. 
Incidentally, I may mention that as the guns were reduced in weight, 
the charge of powder and weight of shell remaining the same, the guns 
were most destructive to their carriages; a circumstance which we all 
could have anticipated, but one involving a true principle of construc¬ 
tion not sufficiently borne in mind, viz. heavy gun and light carriage. 
I shall have occasion to allude to this further by and by. 
The resistance, then, of pure bronze guns, much below the ordinary 
thickness, gives ample safety from bursting ; while that of guns of the 
ordinary dimensions is so great, that it is almost if not quite impossible 
to burst them. To destroy them, the shortest plan is to heat them to 
redness, and then attack them with a sledge-hammer. Under this 
treatment they tumble to pieces in a surprising manner. 
This statement naturally leads us to the second point—how do bronze 
guns resist the great heat developed by the combustion of the powder ? 
On this point bronze is decidedly deficient; but fortunately in field 
guns the amount of powder burnt in each charge is small, and the 
scoring or erosion consequently of little importance. This scoring, 
moreover, is in nowise detrimental to the accuracy of the shooting. 
