74 ANNUAL OF SCIENTIFIC DISCOVERY. 



the filling, and its firm, true hold in the grooves of the gun; the greased 

 canvas wipes the rifling clean, and leaves the bore in a condition to receive 

 readily the next charge, and which is also a sure protection to the bore 

 from injury in loading, and when the gun is discharged. These conditions 

 commend the guns and projectiles to the favorable consideration of the 

 government." 



THE ARMSTRONG GUN. 



The "Armstrong rifled cannon/' which has excited so much attention 

 during the past year, and which has been adopted by the British Govern- 

 ment, is constructed as follows : Each gun is made in about three-feet 

 lengths, and on much the same principle as the twisted gun barrels. Thin 

 bars of the best wrought iron, about two inches broad, are heated to a white 

 heat, and in this state twisted and welded together in spiral rolls round a 

 steel bar or core, smaller in diameter than the bore of the gun. Over this, 

 when cold, another twist of the same kind is made, with the spiral running 

 in a contrary direction, and so until three or four layers have been put on, 

 according to the calibre of the gun and the thickness required. The whole 

 is then reheated and welded together for the last time, under the steam ham- 

 mer. The edges of the three-feet lengths are next planed down so as to ad- 

 mit their joining and lapping over, and over these edges are forced on thick 

 wrought-iron rings, which, being welded down at a white heat, of course 

 contract so as to make the joint almost stronger than if made in one piece. 

 In the breech an opening is cut down into the chamber, but the breech itself 

 is separate from the gun, and is worked backwards by a powerful screw. 

 When the gun is to be loaded, the breech is worked back, and a wedge-shaped 

 piece, fitting into the opening of the gun, lifted out, but not to admit the 

 introduction of the charge, which is pushed forward M'ith a ramrod at the 

 back, working through the large screw in which the breech turns into the 

 chamber, where the rifling begins. The wedge is then replaced, the breech 

 screwed close by a single turn of the lever handle, and the gun fired. The 

 operation of loading and fmng can be performed, we believe, three times in 

 one minute. Apart from the simple but effective mechanism of the breech, 

 the great merit of this gun consists in the manner in which it is formed in 

 spirals of metal bands, which give it such an enormous increase of strength 

 that one-half the thickness of iron can be dispensed with. Thus, an ordi- 

 nary long thirty-two-pounder Aveighs 57 cwt., and requires 10 Ibs. of powder 

 to throw a ball to its utmost effective range, 3000 yards. Sir W. Armstrong's 

 thirty-two-pounder only weighs 26 cwt., and a charge of 5 Ibs. of powder 

 throws its shot 5i miles, or nearly 10,000 yards. In a thirty-two-pounder of 

 this latter kind there are no less than forty-four rifle grooves, having one 

 pitch in ten feet, or making one complete twist round the inside in a gun of 

 that length. A greater pitch would no doubt give greater impetus to the 

 shot, but the risk of "stripping" the lead was so great that it could not be 

 attempted. The shot used are iron, and cylindrical, and at first were com- 

 pletely coated over with lead ; but this plan has just been altered, and the 

 shot have now only two rings of lead | inch thick, and H inches broad, one 

 at the shoulder and one at the base of the cone. Both these rings are dove- 

 tailed, so to speak, into the iron shot, so as to leave about one-tenth of an 

 inch to fit the rifling. Thus, when the cartridge is ignited, the ball is forced 

 forward from the chamber into the narrow bore, which it fits so closely, 



