involved in the Construction of Artillery. 



229 



ductile alloy, embracing in a state of extreme comminution throughout its mass 

 another harder and more elastic one ; and thus singularly analogizing -with the 

 constitution of the best cast-iron for gun founding ; the mottled (/ante trui(i'), 

 of -svhich -we have already treated, -^vhich consists throughout its mass, as stated, 

 of a soft, minutely graphitic iron, embraced by a disseminated, hard, -white, and 

 lamellar metal, -whose carbon is all chemically combined. Thus: — 



These in whole numbers approach nearest to — 



"We thus find that the gun-metal No. 3, consisting of 100 copper + 11 tin 

 (which, after repeated trials and long experience, was fixed by Statute in Oct., 

 1769, as the only alloy to be used for French cannon, having been found the best), 

 has in reality a very simple and almost precise atomic constitution ; for the small 

 excess per cent, in tin, as put into the furnace, namely, the difference between 

 9'910 and 9 880 per cent., will be just about eliminated in the alloy by oxidation 

 in melting, leaving the gun-metal almost precisely 17 Cu + Sn, and most probably 

 this more stable alloy is the basis of several others above and, below it in the 

 scale. 



169. The exuded alloy from the centre of the mass was found by Dussausoy 

 to have the constitution (Cug + Sn), or, as he says, an atom above or below, 

 in copper, which, on referring back to Table x., is, we find, the harder and 

 more elastic of the two, — we can then deduce the following rational formula as 



VOL. XXIII. 2 II 



