The nations of antiquity understood and practised engraving, that is to say, the art of representing things by incised outlines on metal, stone, or any other rigid substance. Setting aside even those relics of antiquity in bone or flint which still retain traces of figures drawn with a sharp-pointed tool, there may yet be found in the Bible and in Homer accounts of several works executed by the aid of similar methods; and the characters outlined on the precious stones adorning the breastplate of the high-priest Aaron, or the scenes represented on the armour of Achilles, might be quoted amongst the most ancient examples of the art of engraving. The Egyptians, Greeks, and Etruscans have left us specimens of goldsmith's work and fragments of all kinds, which, at any rate, attest the practice of engraving in their countries. Finally, every one is aware that metal seals and dies of engraved stone were in common use amongst the Romans. Engraving, therefore, in the strict sense of the word, is no invention due to modern civilisation. But many centuries elapsed before man acquired the art of multiplying printed copies from a single original, to which art the name of engraving has been extended, so that nowadays the word signifies the operation of producing a print. Of engraving thus understood there are two important processes or methods. By the one, strokes are drawn on a flat surface, and afterwards laboriously converted by the engraver into ridges, which, when coated with ink, are printed on the paper in virtue of their projection. By the other, outlines, shadows, and half-tints are represented by incisions intended to contain the colouring matter; while those parts meant to come out white on paper are left untouched. Wood-cutting, or engraving in relief, is an example of the first method; while to the second belongs metal-work or copperplate engraving, which we now call engraving with the burin, or line engraving. In order to engrave in relief, a block, not less than an inch thick, of hard, smooth wood, such as box or pear, is used. On this block every detail of the design to be engraved is drawn with pen or pencil. Then such places as are meant to come out white in the print are cut away with a sharp tool. Thus, only those places that have been covered beforehand by the pencil or the pen remain at the level of the surface of the block; they only will be inked by the action of the roller; and when the block is subjected to the action of the press, they only will transfer the printing ink to the proof.