1879. J on the * Thunderer ' Gun Explosion. 223 



body of the iron is raised to tlio full welding point, and then the door 

 being opened a pair of tongs nearly GO feet long and weighing in them- 

 selves as much as 22 tons, grasj) the coil, withdraw it from the furnace, 

 and place it on the anvil of a 40-ton steam hammer which, beating 

 on the top of the coil, welds each convolution to its neighbour, and 

 makes that which was before but a ringlet, into a tube. It will be 

 seen from the foregoing description that the fibre of the wrought bar 

 goes round about the gun. After the forging, the coils are turned in 

 a lathe and are bored to such dimension as will not quite allow of 

 their being placed when they are cold outside the steel tube, but on 

 being suitably heated they expand sufficiently to admit of the tube 

 being inserted within them, and then in cooling they shrink upon 

 the tube and embrace it firmly. Similarly the C coil is shrunk upon 

 the breech piece. 



This making of the rear end of the gun in two layers outside the 

 steel tube by shrinking the C coil upon the breech piece, is not done 

 with the mere object of reducing the weights of the 23ieces to be 

 handled, but with the further and more important object of obtaining 

 greater assistance from the metal in the gun to resist explosion. I 

 regret very much that time will not permit of our investigating this 

 interesting subject ; I will content myself by saying that if there were 

 no countervailing considerations, the gun which would give the 

 greatest strength for the weight of metal employed in it would be one 

 made up of a large number of very thin coils shrunk one upon 

 another. To put it popularly, if the outside coil, the C coil, is in a 

 state of tension owing to shrinkage, then it is on its guard and is 

 prepared to assist the breech piece and the tubes within it in resisting 

 the strain produced by the explosion ; while if the C coil were not in 

 that state of tension, the tube and the breech piece might be split 

 by the pressure before the strength of the outer coil was brought to 

 their aid. You will see from the diagram that the extreme diameter 

 of the gun is as much as 57J inches ; while its extreme length is as 

 much as 19 feet 2 inches ; its weight, as we all know, is 38 tons ; and, 

 as I have said, the bore of this gun is 12 inches, which is the bore 

 also of its fellow, the bore of the other 38-ton guns in the service 

 being as much as 12J inches. 



You are all aware that the modern projectile is not a sphere, but a 

 cylinder with a pointed end, and that these projectiles are from 2J to 

 3 diameters in length. The cannon ball is a thing of the past. 

 You are also probably aware that it would be im2)ossible to shoot 

 cylindrical projectiles of these proportions for even a short distance 

 without the risk of their turning sideways and of going anywhere but 

 where they were wanted to go, unless a rotary motion were given by 

 the rifling. You will observe in Diagram 1 the rifle grooves are 

 shown commencing at 27^ inches from the rear end of the bore and 

 reaching to the muzzle. There are nine of these grooves, each of 

 them 1^ inch wide by ^ of an inch deep. 



Diagram 3 represents that which is called a " develo2)ment " of 



