impression. This printed part is the raised surface, which is rarely ever more than one-sixth of the area occupied by the types, and is often less than one-twelfth. The resistance to impression of types as compared with stones or plates is, at least, in the proportion of one to six.
As relief plates or types are more quickly coated with ink, and need less impression than lithographic stones or copper plates, the typographic process is, consequently, better fitted to receive the help of labor-saving machinery. The daily performance of the typographic hand press on plain work has been, almost from its earliest employment, about fifteen hundred impressions, which is about four times greater than that of the hand lithographic press. By the use of steam and of improved machinery, this inequality is put almost beyond comparison. The typographic single-cylinder type-printing machine can print fifteen hundred impressions in an hour, and the new newspaper perfecting press can print fifteen thousand perfect sheets in an hour.
The feature which gives to typography its precedence in usefulness over all other branches of the graphic arts is not so much its superior adaptation to impression as its superior facility for combining letters. Its merit is in the mobility of its types and their construction for combination. Printing is Typography. The printing which disseminates knowledge is not the art that makes prints or pictures; it is, as Bernard has defined it, "the art that makes books." The definition is not scientifically exact, but it gives a clear idea of the great breadth of the art. In its perfect adaptation to this great object, the broad generalization of the definition in the dictionaries may be justified. The method of printing which is most useful may rightfully claim the generic name.
Xylography is the scientific word for the art of making engravings on a single block of wood, in high relief, for use on the typographic printing press. A xylographic block may be an engraving of letters only, of pictures only, or of both letters and pictures, but in all cases the engraving is fixed on
