ON METALS FOR ORDNANCE. 101 



the oxidation of the shot, especially with undue rapidity of firing, soon change 

 the central axis ; and alludes to the grooved and abraded state of the guns 

 which have been returned, in proof of his assertion. He points out the 

 necessity of experiments to ascertain how much of the heating of the gun is 

 due to friction, and urges that, for special service at any rate, polished shot 

 accurately fitting the gun should be provided. He points out the great 

 efficiency of the guns used at the siege of Gaeta, in 1815, in which he took 

 an important part ; and considers that some guns of that date should be 

 examined and the quality of the metal of which they are composed, ascer- 

 tained. He believes that the greater heat at which metals are now fused, 

 and the more perfect fluidity attained, facilitate an undue rapidity of cry- 

 stallization, and, according to his idea, impair the cohesive strength of the 

 metal. In consequence of the vents giving way before the bore is injured, 

 he proposes the use of screw vents, ly inch in diameter, and as hard as 

 fowling-piece nipples. He considers that even the whole breech might be 

 cast separate, of a denser material than the rest of the gun ; and that tliis is 

 proved by the ancient forms of guns, by the Chinese gingals, and by the 

 revolving rifles and pistols of Colt and Adams. In conclusion he affirms 

 that four-fifths of the present expense might be saved by the use of the best 

 guns our engineers can produce. 



There is some truth in Sir Edward's remarks on the abrasion or grooving 

 of the gun. The two opposite forces of propulsion and recoil act equally on 

 the breech as on the ball, but in different directions ; and if the ball does 

 not accurately fill the bore, it has a tendency to expend part of its force on 

 the sides of the gun, and to cause rupture near the trunnions. Under such 

 circumstances, the gun is subject to several distinct strains : one on the 



T-ig. 1. 



breech in the direction of the arrow a ; another in the line of the bore in 

 the direction of the arrow b; and a third from the pressure of the ball upon 

 one of the sides as at c, causing a strain in the direction of the arrow d. 

 These forces, when in action at the same time, tend to rupture the gun at 

 the trunnions, by tension on the line of discharge a b, and by a transverse 

 strain at c, caused by the pressure of the ball in the direction of the line d. 

 In guns of great length, a perfectly true bore and an oblong or cylindrically 

 turned ball, fitted like the piston of a steam-engine, would doubtless cure 

 this defect and prove advantageous, by giving greater safety to the gun, by 

 diminishing the friction, improving the windage, and ensuring a more direct 

 line of flight to the projectile. There are difficulties in casting and fitting 

 guns on this principle, which may however be overcome by strict attention 

 to sound rules of construction. 



Extracts from a letter addressed to the Committee by Mr. James Nasmyth, 

 dated Patricroft, Sept. 19th, 1855. 

 Mr. Nasmyth, so well known as the inventor of the steam-hammer, 

 commences his letter by entering on the subject of the failure of malleable 

 iron guns. He states that those which are built of bars, welded together, are 

 sure to be destroyed sooner or later by the continued disruptive force of the 



