a 



involved in the Construction of Artillery. 231 



gravity, or of change of affinity with temperature, &c., but in the competency 

 of copper and tin to form two sets of alloys, whose respective combining 

 ratios are such as to render secondary combination in the alloys themselves 

 impossible. It might be presumed that the addition in small proportion of a 

 third metal, capable of combining with both alloys, would unite them, and 

 improve the physical properties of the whole. This does not, however, seem 

 to be indicated by the very numerous, though most desultory and unsystematic, 

 trials of ternary alloys, made at various periods and places, numbers of which 

 may be found recorded in the works of Herve and of Meyer. The whole 

 subject of bronze gun-casting and of the gun-metal is, as it were, yet to be 

 investigated ; and success can only attend this when, for the first time, it shall bo 

 commenced and pursued in a truly philosophical spirit, and with the full aids 

 of Chemistry and Physics combined. 



170. It is probable, therefore, that Nos. 1, 2, and 4, and many other gun- 

 metals besides, consist when cast of the normal metal (Cu,? + Sn), with one or 

 more subordinate alloys, exuded or not, and with or without a proportion of 

 separated copper ; in other alloys of different proportion, a similar segregation 

 may occur, with separation of a portion of tin. But that there is no advantage 

 gained necessarily, by mere complexity of constitution, is pretty obvious from 

 the normal and simple alloy being found in practice the best ; the only quali- 

 fication being, that in French arsenals it is considered, that for small and light 

 guns below nine-pounders, 100 copper -t- 8 tin is better, the alloy 100 copper -^ 11 

 tin being used for all above. 



171. Where the atomic constitution is complex, and especially where the 

 tin is in excess, the affinity of the alloy seems to reach its extreme of inco- 

 herence. Thus Berthier found that an alloy which had been found decisively 

 defective in quality for guns, and which was submitted to him for analysis 

 (Ann. des Mines, t. vii., 3'° ser.) had the composition — 



Copper, 83-8 



Tin, 15-7 



Lead, 0'5 



Neglecting the lead, as no doubt accidental, though most prejudicial to 

 the qualities of the alloy, the composition of this metal approaches to 9'66 



2 II 2 



