Page:De Vinne, Invention of Printing (1876).djvu/28

18 action or the impress of light makes a photograph. Under different conditions, the pressure of the breath makes hollow glassware. Moulding, coining, stamping and embossing are other methods of impression; but the men who practise these methods are not known as printers. The word printing has acquired a conventional meaning not entirely warranted by its derivation. It means much more than impression. It is commonly understood as a process in which paper and ink are employed in conjunction with impression.

Printing and typography are not strictly synonymous, as may be inferred from the definitions. Typography, although the most useful, is not the only form of printing. Printing on paper with ink is done by four methods. Each method is, practically, a separate art, distinct from its rivals in its theory, its process, and its application. These methods are:

Steel-plate or Copper-plate printing, in which the subject is printed from an etching or engraving below the surface of a plate of steel or of copper.

Lithography, in which the subject is printed from a transferred engraving on the surface of a prepared stone.

Typography, in which the subject is printed from a combination of movable metal types cast in high relief.

Xylography, in which the subject is printed from a design engraved on a block of wood in high relief.

The distinct nature of the substances in use for printing surfaces by the four methods should be enough to teach us that the methods are entirely different. But the manner in which the letters, designs or figures of each method are put on the respective printing surfaces will show the differences more noticeably. In typographic and xylographic work, the matter to be printed is cast or cut in high relief, or above the surface; in lithographic work, it is put on the smooth surface of the stone, in relief so slight that it is almost level with the surface; in steel and copper-plate, it is cut below the surface which receives the impression. The illustration on the next page shows, but in an exaggerated form, the appearance of a