56 ANNUAL OF SCIENTIFIC DISCOVERY. 



semi-cylindrical form, and then welding them together at the edges. In this 

 way a cylinder is obtained in which the fibre of the iron is arranged longi- 

 tudinally, instead of transversely as in the other rings. This arrangement is 

 adopted because that part of the gun has to sustain the principal force of the 

 thrust upon the breech, on the discharge. It is into this portion that the 

 breech-screw made of steel fits, by means of which a movable plug of 

 steel, provided with a soft copper washer, is pressed up against the end of 

 the barrel when the gun has been loaded. The breech-screw being hollow, 

 the charge is introduced through it into the gun, on the removal of the plug. 



This gun, built up of so many pieces, accurately welded, and turned, and fit- 

 ted, with its thirty or forty grooves, its neat lever arrangement for working 

 the breech-screw, its admirable sights for giving direction, and various other 

 arrangements, contrived so as to render it a most complete and perfect 

 weapon, is undoubtedly very costly as compared with the ordinary cast-iron 

 gun. But, owing to the admirable system of manufacture, and the beautiful 

 mechanical appliances brought to bear upon the production of each part, the 

 original cost of the gun has already been very much diminished. On com- 

 paring the price of a twelve-pounder gun with that of a bronze gun of the 

 same calibre, which it has now superseded, the latter is found to be about 

 double the expense. The price of iron used for the manufacture of the 

 Armstrong gun is nineteen pounds per ton. It is the best description of 

 malleable iron, bearing a tensile strain of about seventy -four thousand pounds 

 on the square inch. The present cost of a twelve-pounder gun, weighing 

 eight hundred weight, is about ninety-three pounds. The value of gun-metal 

 is about one hundred and twenty-five pounds per ton; and the cost of a 

 twelve-pounder gun of this material, weighing nineteen hundred weight, is 

 one hundred and seventy -five pounds ten shillings. Of the latter, it may be 

 said, that when no longer serviceable it may be recast, while an old Armstrong 

 gun cannot be reconverted into a new one. But, on the other hand, the 

 average number of rounds which can be fired from the old gun before it is 

 unserviceable scarcely exceeds one thousand; while the limit to the power 

 of endurance of the Armstrong gun is not yet known. Between five and six 

 thousand rounds have been fired from one, without any vital injury to the 

 gun. 



While these important results have been obtained with guns of wrought 

 iron, built of rings, others, scarcely less valuable, have attended the applica- 

 tion of materials, varying in their nature between steel and malleable iron, to 

 the production of light guns, cast in one piece. M. Krupp, of Essen, was 

 the first to produce masses of cast steel of sufficient size for conversion into 

 cannon. A twelve-pounder gun, cast of this material, was experimented 

 upon in this country several years ago, and exhibited the most extraordinary 

 powers of endurance, having withstood the heaviest proofs without bursting. 

 Similarly good results were obtained with cast steel in France and Germany, 

 and it is now applied to the construction of the rifled field-guns in Prussia. 

 A cast material, somewhat similar in character to this steel of M. Krupp, 

 and to which the name of homogeneous iron has been given, has recently 

 received most successful application in the hands of Mr. "Whitworth, not 

 only to the production of the barrels for his rifle small arms, but also to 

 the manufacture of his beautiful rifle-cannon. The smaller cannon are cast 

 in one piece, and then forged to the required form. The heavy guns 

 eighty and hundred pounders consist, however, of cylinders of homoge- 

 neous iron, upon which hoops of fibrous iron are forced by hydraulic pres- 



