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size from 15 inches smooth bore, down to 13-pounders, as many as 150 instances of guns bursting while being fired; while, as I have already mentioned, there were instances of spontaneous bursts, in 10 guns.
Last Tuesday evening's papers contained the report of the bursting of a gun at Genoa. I believe I am correct in saying that this was a 12¾-inch gun, having a cast-iron body reinforced with steel hoops of German manufacture; that it was firing a 760 lb. projectile with the low charge of 170 lbs. of powder, and that it blew the breach out.
With respect to the rapid wearing out of large guns. I wonder to how many of those present, or indeed, to how many of the public who interest themselves in guns, it has occurred, to consider the facts as regards the wear on large guns as compared with that on small guns. Let me show you why it is that the erosive power of the gases per unit of surface, must be so much more in a large gun, than it is in a small one. Let us take, say a 6-inch gun and a 12-inch gun, and assume that the linear dimensions of the 12-inch gun are just double, in all respects of bore, powder-chamber, and projectile, those of the 6-inch gun.
Then obviously the linear dimensions being doubled, the projectile of the 12-inch gun will be eight times as heavy as that of the 6-inch, for the weight will increase as the cube of the linear dimensions, and the powder-charge will also be eight times as heavy, and will produce eight times as much gas. But the area of the bore of the gun will increase only as the square of the doubled dimensions, and will therefore be in the 12-inch gun, only four times the area of the 6-inch; but this area of four times, has to afford passage to the gases of eight times the weight of powder, and thus the rate of erosion is inevitably increased, as the guns become larger and larger. This is an inexorable law, and one to which all guns, whether British or foreign, are equally subject. There is no help for it; but provision can be made, and is made, to render the reparation comparatively simple and inexpensive.
