Fotocopia.

The discovery by primitive man that certain kinds of stone or mineral would yield a metal on application of heat, made possible an advance in civilization relatively as important as any that has followed. Metal implements superseded the more elumsy and inadequate tools of stone , and metallurgy became an established science. Broze, an alloy of copper and tin, is obtained by smelting these metals together in proportions which may be varied according to the nature of the product required...