possible under the old mechanical methods. In woodcutting, as in photo-engraving, every thing that is to appear white in the design is cut away, while the black and gray lines are left in relief. It is not easy to make a comparison in regard to the relative expense of the two methods, because this greatly depends upon the character of the design from which an illustration is to be made. With the photo-plate it is of little consequence how great the detail of the drawing may be so long as this appears in plain black and white lines. In the wood-cut, however, the expense is entirely dependent upon this matter of detail, an intricate design of three inches square costing perhaps more than another of three times the size but of more open character.

Photo-lithographic and Heliotype processes both produce somewhat the effect of a photograph, and for a certain class of illustration their use may be advantageous. The objection to them, however, is that they must be printed separately and not with the text of the book, and the expense of producing them is thus considerable, while the cost of binding is increased by the necessity of pasting in separate sheets of illustrations. The use of these methods can only, as a rule, be recommended for books of limited editions.

Lithograph. In lithography the illustration is engraved and printed upon stone. For the finer description of medical plates, and for colored designs of fruits, flowers, and foliage, this method is most effective. The printing is, however, very slow and expensive work, as the sheet has to pass through the press separately for each color.

Copper and Steel Plate.—Books illustrated by means of etchings on copper present, if the work be artistically done, the most thoroughly satisfactory method of producing the tone and feeling of the artist's design. In etching the copper

plate is covered with a coating of thick, prepared varnish or wax. The surface being now smoked, the artist draws his design upon the blackened surface, after which the lines are cut through the varnish with a sharp-pointed instrument. The plate is then covered with acid, which eats away the copper where the lines are drawn through the wax, leaving the rest of the plate intact. Aside from the drawing, much here depends, in the result, upon the good judgment of the artist in the length of time he permits the acid to act; if the action is too long the plate may be entirely ruined.

The cost of making the Steel Plate is much greater than that of the etching, the design in this case being cut upon the steel with great labor and care with a tool called the graver. This is the most expensive method of making a book illustration, and is now rarely used except for portraits.

Both the etching and steel-engraving require much time to print, and are thus expensive for ordinary book-illustrating purposes. Moreover the same objection exists as to their use as with the photo-lithographic engraving—the printing having to be done by a separate process, and not with the text of the book.