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 of them, while presenting many differences in detail, presents certain broad characteristics in common which distinguish them from the raw material of other crafts. Whether they are found native in the metallic state as is usual in the case of gold, or combined with many other minerals in the form of ore as is more common with other metals, fire is the primal agency by which they are made available for our needs. The first stage in their manipulation is to melt and cast them into ingots of a size convenient to the purpose intended. Secondly, all these metals when pure, and many alloys, are in varying degree malleable and ductile, are, in fact, if sufficient force be applied, plastic. Hence arises the first broad division in the treatment of metals. The fluid metal may, by the use of suitable moulds, be cast at once to the 69