MECHANICS AND USEFUL ARTS. 45 



There are two great points as to which Mr. Whitworth's barrels differ from 

 Sir William Armstrong's. In the first place, they are not, as his are, provided 

 with a chamber in which the charge reposes, but are rifled throughout, from 

 breech to muzzle. The great advantage of this is, that any amount of load- 

 ing, and any length of projectile, can be employed; Avhereas, in Sir William 

 Armstrong's, the charge has to be invariably accommodated to the size of the 

 chamber. Mr. "VVhitworth says that there would not be the least difficulty 

 in firing a projectile half the length of the barrel, should occasion require it; 

 and he actually contemplates firing a two hundred pound shot out of his 

 eighty-pound gun, when it is duly furnished with the carriage which is now 

 being prepared for it. In the next place, instead of being fluted with a num- 

 ber of little sharp-edged grooves, the new barrel is a simple hexagon, with 

 its sides made perfectly smooth, so as to offer the least possible resistance to 

 a body passing over their surface, and thus obviating the dangers which 

 might otherwise result from so considerable a pitch of rifling as that which 

 Mr. Whitworth employs. The pitch of rifling in the three-pounder is one 

 inch in forty; and thus the projectile makes one and a half revolutions before 

 leaving the ban-el, and the most intense rotatory motion, and, consequently, 

 the greatest accuracy of flight, are thus obtained. Notwithstanding this violent 

 twist in the barrel, which some people have imagined must lead to frequent 

 explosions, Mr. Whitworth has contrived that there shall be extremely little 

 friction. This is managed by the projectile fitting the ban-el, and being 

 allowed to slip over its surfaces, instead of being made slightly larger than 

 the barrel, and being thus forced to cut into its edges. 



In the Armstrong gun, the projectile, in forcing its way out, drives its 

 leaden coating into the grooves of the barrel. In the Whitworth gun, the 

 projectile glides over the surfaces of the barrel, and passes out with a very 

 inconsiderable degree of resistance. The form of projectile which is found 

 to answer best, and with which the great distances have been accomplished, 

 is an oblong conical bolt, rifled so as to fit the barrel. In the three-pounder 

 it is about nine inches long, and in shape is like a little cucumber with one of 

 its round ends cut off, and six spiral slices cut longitudinally in its rind, 

 these being, of course, for the purpose of fitting the hexagonal bore. The 

 length of the projectile, however, is not an essential point, and so long as its 

 rifle exactly fits the barrel through which it is to pass, it may be longer or 

 shorter, or a perfect sphere, as convenience or fancy may suggest. When the 

 gun is to be loaded, the breech of the cannon screws off, and the bolt is 

 pushed into the barrel. At its back is placed a tin cartridge, similarly rifled, 

 and so arranged as to protrude slightly from the barrel, till the cannon's 

 breech is again screwed on; so that, when the gun is fastened up, the car- 

 tridges line that part of it at which its breech and body join, and prevent the 

 possibility of the slightest escape of air or powder through any interstice 

 that might be occasioned by an imperfect fitting of the screw. It has also 

 the advantage of confining the powder at the moment of explosion, and so 

 saving the gun's metal from the full strain of pressure to which it must 

 otherwise be exposed. 



But the cartridge has still a farther use. At the end where it touches the 

 projectile it is furnished with a little lump of lubricating matter, which is 

 disbursed by the explosion over the interior of the barrel, and cleans it for 

 the next discharge, besides effectually preventing the least windage. Two 

 hundred rounds can be fired without the barrel fouling; and the great incon- 

 venience of having to sponge out the barrel after every shot, and of being 

 obliged to carry water with the gun for this purpose, is altogether avoided. 



