92. Printing from wooden blocks. A block of box wood is, in this instance, the substance out of which the pattern is formed: the design being sketched upon it, the workman cuts away with sharp tools every part except the lines to be represented in the impression. This is exactly the reverse of the process of engraving on copper, in which every line to be represented is cut away. The ink, instead of filling the cavities cut in the wood, is spread upon the surface which remains, and is thence transferred to the paper. 93. Printing from moveable types. This is the most important in its influence of all the arts of copying. It possesses a singular peculiarity, in the immense subdivision of the parts that form the pattern. After that pattern has furnished thousands of copies, the same individual elements may be arranged again and again in other forms, and thus supply multitudes of originals, from each of which thousands of their copied impressions may flow. It also possesses this advantage, that woodcuts may be used along with the letterpress, and impressions taken from both at the same operation. 94. Printing from stereotype. This mode of producing copies is very similar to the preceding. There are two modes by which stereotype plates are produced. In that most generally adopted a mould is taken in plaster from the moveable types, and in this the stereotype plate is cast. Another method has been employed in France: instead of composing the work in moveable type, it was set up in moveable copper matrices; each matrix being in fact a piece of copper of the same size as the type, and having the impression of the letter sunk into its surface instead of projecting in relief. A stereotype plate may, it is evident, be obtained at once from this arrangement of matrices. The objection to the plan is the great expense of keeping so large a collection of matrices. As the original composition does not readily admit of change, stereotype plates can only be applied with advantage to cases where an extraordinary number of copies are demanded, or where the work consists of figures, and it is of great importance to ensure accuracy. Trifling alterations may, however, be made in it from time to time; and thus mathematical tables may, by the gradual extirpation of error, at last become perfect. This mode of producing copies possesses, in common with that by moveable types, the advantage of admitting the use of woodcuts: the copy of the woodcut in the stereotype plate being equally perfect. with that of the moveable type. This union is of considerable importance, and cannot be accomplished with engravings on copper.