The work of the engraver, like many other phases of reproductive art, is a fruitful source of mannerisms; yet even these will produce excellent results if they create innovations which will be afterwards approved and recognised as healthy, independent, and entirely original methods. [Illustration: Fig. 4.--Modern Wood Engraving. "An interpretation of tone and texture by an arrangement of lines." _Block supplied by the London Electrotype Agency Ltd., from the "Religious Tract Society."_] CHAPTER VII _PHOTO "PROCESS" ENGRAVING_--A PROGRESSIVE PROCESS--COMMERCIAL AND ARTISTIC FEATURES--"LINE" PROCESS--"HALF TONE"--ARTISTIC RESTORATION--TRI-CHROMATOGRAPHY--PHOTOGRAVURE "It is not knowledge itself which is power, but the ability to use and apply knowledge." =A Progressive Process.=--Photo process engraving is a method of graphic reproduction which comes into direct contact with art in its most popular phases. It is a distinctly progressive process which possesses immense advantages and represents an effective and by no means inartistic aspect of the graphic arts. The lavish, and in many instances extravagant, employment of process engraving for purposes of pictorial illustration is a substantial proof of its popularity and illustrative value. It may not always reach a high standard of artistic realisation, but it is almost invariably realistic and attractive in its varied forms of representation. The idea of pictorial illustration, whether as the translation of an artistic conception or an actual representation of current events, has ever been a fascinating one; and its evolution, from a photo-mechanical standpoint, has been one unbroken record of remarkable progress. To enter upon a detailed exposition of any of the many photo-mechanical processes is somewhat beyond the purpose of this short treatise, and to attempt anything but a full and comprehensive description on such lines would be both unwise and valueless. Let it suffice, then, to indicate their more salient points, their illustrative and artistic value, and the manner in which they may be most successfully applied. =Commercial and Artistic Features.=--The commercial advantages of photo-engraving may be summed up in a very few words:-- 1. The plates can be produced quickly and economically. 2. The impressions can be made at a high rate of speed, and in some of the processes without perceptible deterioration. 3. The prints will be more or less facsimiles of the original.