220 Mr. Mallet on the Physical Conditions 



152. It is easy, then, to understand, how widely mistaken have been the 

 estimates of Mr. Nasmyth* and others, as to the comparative resistances, of 

 wrought and of cast-iron, for ordnance, in assuming the former at six times the 

 strength of the latter. 



Much more extended experimental information is yet needed, however, to 

 bring these conditions into a state to be applied with perfect assurance, in 

 calculation and practice. 



19. — Gun-Metal or Bronze as a material for Cannon. 



153. We have already considered some of the physical properties of gun- 

 metal in relation to the other materials for cannon, in treating of the effects of 

 unequal expansion by heat; but in order fully to compare the relative values of the 

 four great classes of materials, for the construction of ordnance, viz., cast-iron, 

 wrought-iron, steel, and gun-metal, it is necessary to treat more at length of the 

 physical, and especially, the chemical properties of the latter alloy. Gun-metal, 

 probably the very earliest used material for cannon, is that which has received 

 the least improvement or systematization of our knowledge as to its use, up to 

 the present hour, — the archasologist finds the rude weapons of Scandinavian, 

 Celtic, Egyptian, Greek, and Roman warfare, formed of nearly the same alloys 

 of copper and tin, and in about the same proportions, as the cannon of to-day.f 



This has resulted, not from total neglect of the subject, nor from insuperable 

 difficulties, but because a result, considered " good enough" in practice, has been 

 arrived at, in the chief gun-foundries of Europe long since, and because whatever 

 experiments have been undertaken to improve (so far as any such have been 

 published) have proceeded with little system, and in the hands of men, not 

 possessing the indispensable qualifications for success, namely, an accurate and 

 extensive acquaintance, with both chemical metallurgy, and physics, on the one 

 hand ; and with the demands of the artillerist, and the practical devices, ex- 

 periences, and skill of the founder, upon the other. 



Such an inquiry remains still to reward the labour, and well-directed know- 

 ledge, that shall be bestowed upon it, and should gun-metal always continue to 



* See Mr. Nasmytli's letter to " The Times," November, 1854. 



I See Dr. J. W. Mallet's " Chemical Enquiry into the Metallic Antiquities of the Royal 

 Irish Academy Museum." Trans. E. I. A., vol. x.xii. 



I 



