Pot Metal (copper and lead) is improved by the addition of tin, and the three metals will mix in almost any proportions: when the tin predominates, the alloy so much the more nearly approaches the condition of gun-metal. Zinc may be added to pot-metal in very small quantity, but when the zinc becomes a considerable amount, the copper takes up the zinc, forming a kind of brass, and leaves the lead at liberty, and which in great measure separatee in cooling. Zinc and lead are also very indisposed to mix alone, although a little arsenic assists their union by " killing " the lead, as in shot metal. Antimony also facilitates the combination of pot-metal; 7 lead, 1 antimony, and 16 copper, mix perfectly well the first fusion, and the alloy was decidedly harder than 4 lead and 16 copper; and apparently a better metal. "Lead and antimony, though in small quantity, have a remarkable effect in diminishing the elasticity and sonorousness of the copper alloys."