ARTILLERY 



241 



wrought-iron bars into cylinders and combining them in the manner described, there 

 appears to be no great difficulty in so doing, if proper apparatus bo provided for the 

 purpose. It would not, however, be advisable (except in peculiar cases) to apply the 

 principle of loading at the breech except to guns of small dimensions, because in heavy 

 ordnance the moveable parts would become too cumbrous to be conveniently handled.' 



The essential features of the Armstrong method of construction are : 



1st. The disposal of the fibre of the metal round the bore by coiling, so as to 

 resist the tangential strain, the welds running in the direction of the least strain as 

 regards their separation. 



2nd. The employment of a breoch-piece, to support the bottom of the bore, with 

 the fibre running lengthwise so as to resist longitudinal strain. 



3rd, The shrinking-on the different portions, so that the exterior of the gun takes 

 a due share of the strain. Mr. Whitworth's method of building-up is as follows : 

 ' The tube of the gun is made taper, being in tho 5|-inch-bore gun 1 inch larger in 

 diameter at the breech end than at the muzzle end ; then a series of hoops are made, 

 which are screwed together so as to form another tube, that is put on by hydraulic 

 pressure ; each layer is put on a little tighter than the succeeding one.' Evidence 

 Report on Ordnance. 



The method of Closing the bore of a built-up gun is an important question. The 

 iuner tubes of some of the large M. L. orduance lately constructed in tlie Royal Gun 

 Factories, as well as those of some of Blakely's guns, have what are termed closed 

 ends, that is, the tube is not bored through to the bottom ; the solid end of the tube 

 in sen-ice-guns is supported by a cascable screwed into the breech-piece, and in 

 some of them also by a shoulder in the breech-piece. Sir W. Armstrong, Mr. Whit- 

 worth, and Major Palliser use open tubes and close them by a plug of wrought-iron 

 or copper. The cascable in the Whitworth guns is not, like Armstrong's, cylin- 

 drical in form, but is shaped into two or more (screwed) cylinders, their respective 

 diameters increasing from bore to breech. 



93 



Breech of Armstrong's 10-5-inch gun. 



Breech of Whitworth's 7-inch gun. 



In closing the bore of a M. L. or B. L. gun, one important principle should not be 

 neglected, viz. that as the gas exerts an equal force in every direction, the thickness of 

 the metal should be as great, or nearly so, behind as over the charge. Inattention to this 

 principle, or its sacrifice to other considerations, is a source of weakness in many B. L. 

 guns. One advantage of an open end is, that the metal of the inner tube is relieved 

 to some extent from longitudinal strain. 



Tho relative cost of large ordnance made in different ways was, when the last 

 edition was published, as follows : 



Cast-iron guns ...... 21 per ton. 



Armstrong built-up ditto .... 100 (lately 87J.) 



Krupp's steel ditto . . . . . 170 



Gun-metal ditto 187 



and, excepting the variation due to the price of the metal, it continues relatively about 

 the same. 



Bronze guns are valuable for recasting. Mr. Frazer has introduced modifications, 

 by which it is said the cost of built-up ordnance will be much reduced, viz. to 40J. a ton 

 with a coiled inner tube, and to 551. a ton with a steel tube. Mr. Whitworth told 

 tho Committed on Ordnance that his 5J-inch gun weighing 4 tons, and made of homo- 

 geneous metal (soft steel) cost TOO/., which is about 1 751. per ton. The question of tho 

 relative advantages of breech- and muzzle-loading ordnance has been frequently dis- 



YOL. I. B 



