42 ANNUAL OF SCIENTIFIC DISCOVERY. 



and the iron becomes soft. Repeated melting, then quick cooling, and hori- 

 zontal casting, greatly improve cannon, and all articles made of cast iron. 



HOVT THE ARMSTRONG GUN IS MANUFACTURED. 



A visitor to the works, who has never seen an Armstrong gnn, must, as 

 he witnesses the successive stages of its manufacture, be sorely puzzled to 

 conceive what it will look like when completed; and scarcely less is the 

 surprise of any one who has seen the finished piece, at the strange shapes 

 which its component parts assume during the various processes. Let us 

 begin at the beginning, and observe the various steps, from first to last, in 

 the creation of the most perfect piece of ordnance the world has ever seen. 



Imagine a very long, thin bar of the finest iron, some two inches square, 

 and one hundred and twenty feet in length that is the basis of a twenty- 

 five-pounder. For convenience in the manufacture, this bore is divided 

 into three pieces, about forty feet in length. A hundred-pounder requires 

 three pieces, each of ninety feet in length. The manufacture commences 

 in the forging shop, a vast, dingy shed, where there is an incessant din of 

 hammers and roaring of mighty furnaces, where blocks and bars of iron 

 lie scattered in seeming confusion on every side here almost transparent 

 at white-heat, there glowing red-hot; in one corner sending out showers 

 of sparks under the discipline of a huge steam-hammer, in another hissing 

 and sputtering under a stream ; where stalwart, grimmy men, with uprollcd 

 shirt-sleeves, visors, and leather aprons, are seen looming through the 

 smoke, or, in the full glare of the fires, tossing about red-hot bars with the 

 indifference of salamanders, and making the anvils ring with thirty-Cyclops 

 power. 



"We fix our eyes on a long narrow furnace, in which lie a number of the 

 iron bars we spoke of. Suddenly the door is opened, and a fierce lurid gleam 

 of light is cast through the shop. One of the men seizes the end of a bar 

 in a pair of pincers, drags it forth, and makes it fast to a roller which stands 

 immediately before the furnace, and the diameter of which is equal to the 

 rough-made tube of a twenty-five-pounder when first rolled. The roller is 

 put in motion the bar is slowly and closely wound around it, just as one 

 might wind a piece of thread round a reel. The roller being turned on one 

 end, the spiral tube Xo. one coil it is termed is knocked off, restored to 

 white-heat in another furnace, for it has cooled somewhat in the rolling, 

 and then flattened down and welded under one of the steam-hammers, till 

 only about half as long as it was. For a twenty -five-pounder, the length of 

 the coil after this process is two and a half feet; and three such coils are 

 welded together to form the tube. 



Before that operation is performed, however, each coil is bored in the 

 inside, and pared on the outside, to within a very little of its proper diame- 

 ter, so that the slightest flaw in the welding, if any exist, may be detected. 

 Having passed this test, a couple of coils, brought to a proper heat by being 

 placed end to end in a jet of flame from a blast-furnace, are welded by 

 violent blows from a huge iron battering-ram. A third coil is added to the 

 other two in the same manner, and the tube is complete. Over this a second 

 tube, which has been prepared just in the same way, is passed while red-hot, 

 and, shrinking as it cools, becomes tightly fastened. This is termed " shrink- 

 ing on." Over this again is placed a short, massive ring of forged iron, to 

 which the trunnions or handles of the gun arc attached. 



