THE ROYAL ARTILLERY INSTITUTION. 488 
because the studs of the shell being locked hard against the driving 
sides of the grooves, there is an air-tight joint between them; hence no 
gas can pass. Thus, on examining the grooves of a bronze gun which 
has fired a large number of rounds, you find the lands, loading side and 
bottom of the grooves, pitted by the heat burning the tin out of the 
alloy, and eroding the metal; the driving sides, on the other hand, are 
perfectly free from such pitting. 
One more source of injury to a bronze gun, consists in the effect of 
the accidental and premature explosion of a shell in the bore. Experi¬ 
ments at Shoeburyness with live common shells, having a small hole 
bored through the base, so as to form a direct communication between 
the charge in the gun and that in the shell, prove that no material 
injury is done to the gun beyond a few unimportant scratches. 
5. In the present state of our knowledge, the choice of a metal oT 
combination of metals for a field gun, appears to lie between steel, or 
steel protected by a wrought-iron coil, and bronze. Circumstances may 
have unduly prejudiced me, but I confess I think there is nothing like 
bronze for the roughing of a long campaign, nothing like it for 
simplicity of manufacture, nor for safety from bursting, nor, finally, for 
economy. It is curious to look back and to find that I am expressing 
an opinion held as far back as four and a half centuries. One Capo 
Bianco, publishing in 1598, states that there were bronzp guns in 
existence in 1418. 
Bronze, if bright from the turning-lathe, when exposed to damp air, 
soon oxidizes, and gradually attains the green brown tint so much 
admired in antique statues. After the film of oxide has penetrated .to 
a certain depth, practically the action on the metal ceases, though the 
oxide itself gets a deeper tint by time. This is the explanation of the 
perfect condition of antique bronze statues, and other objects, which 
have been found in certain soils after having been buried for centuries. 
With iron or steel, on the contrary, once oxidation has set in, it goes 
on with increased vigour, and eats away until the whole mass is finally 
oxidized. 
This is why I say bronze is better suited for the roughing of a cam¬ 
paign than steel. 
As to simplicity of manufacture, nothing can be simpler than the 
casting of the block, once you have got apparatus suited to the size of 
your gun.- 
Recollect in making a comparison as regards manufacture between 
bronze and steel guns, you must not confine yourselves to what you have 
seen done in the Royal Gun Factories, you must go to Mr. Firth*s or to 
Sir Joseph Whitworth*s factories, and watch the processes there. I 
will not detain you with an attempt to describe these processes. I will 
confine myself to the statement that the art of casting steel in large 
masses is in its infancy ; that it is necessarily expensive, from the high 
melting point of the metal; and that, in the present state of our know¬ 
ledge on the subject, it would not be advisable to attempt it in India. 
As regards economy, the value of a new bronze gun of 6 or 8 cwt. 
is to the value of an old one in the ratio of 17 to 7. In other words* 
