The presence in greater or less proportions of other metals than copper and tin in bronze antiquities may eventually lead to the recognition of the sources from which in each country the principal supplies of metal were obtained. Professor Sullivan, in the book already cited, arrives at the following among other conclusions from the chemical facts at his command:—
1. The northern nations in ancient times used only true bronzes—those formed of copper and tin—of greater or lesser purity according to the kind of ores used.
2. Many of these bronzes contain small quantities of lead, zinc, nickel, cobalt, iron, and silver, derived from the copper from which the bronze was made.
3. Though some bronzes may have been produced directly by melting a mixture of copper and tin ores, the usual mode of making them was by treating fused crude copper with tin-stone.[1616] In later times bronze was made by mixing the two metals together.
4. The copper of the ancient bronzes seems to have been smelted in many different localities.
Some analyses of bronze antiquities found in other countries are given in the works indicated below,[1617] in addition to those mentioned on page 418.
ANALYSES OF BRONZE ANTIQUITIES.
* In this case oxygen to the extent of 3·83 was present. The bronze had become so friable as to be easily pulverised in a mortar. Mr. J. Arthur Phillips writes about it as follows:—“When a freshly-broken fragment of it is examined under a low magnifying power, it is seen to consist of a metallic net-work enclosing distinct and perfectly formed crystals of cuprite, surrounded by a greyish white substance which is chiefly bioxide of tin. In this alloy the nickel, silver, and iron are evidently accidental impurities, but the lead is no doubt an intentional ingredient.” The specific gravity after pulverization is about 7·26 only.