Bewick, of course, is an outstanding example of an artist who used wood engraving for illustrating natural history; the methods he pursued may be studied in the tailpiece on p. 11, which was printed from an electrotype of the original block. Wood engraving, up to quite recent times, was the method of reproducing text figures; not only for scientific books and periodicals, but also for general literature and journals. Much of this work is of outstanding excellence; for scientific work the following may be studied: Duchartre: _Elements de Botanique_. Paris, 1867. The drawings were made by Riocreux and engraved by Leblanc. Baillon: _Histoire des Plantes_, Paris, 1887. This work contains some beautiful wood engravings, reproductions of drawings by Faguet. Bentham: _Handbook of the British Flora_, London, 1865. The engravings are from drawings by W. H. Fitch. Deschanel: _Natural Philosophy_, London, 1890. The engravings, many of which are of excellent quality, are by Laplante, Rapine and others. In many cases, notably in the representation of the rays of light passing through lenses and also in the illustrations of snow crystals, the use of the white line is admirably demonstrated. Kerner: _Pflanzenleben_, Leipzig, 1888. This contains some excellent engravings by Winkler and others. Le Maout et Decaisne; _Traite general de Botanique_, Paris, 1876. This work contains splendid examples by Riocreux and Steinheil (see Fig. 8). Oliver: _First Book of Indian Botany_, London, 1869. This contains some characteristic work of W. H. Fitch. It does not appear to be generally known that excellent reproductions in colour may be obtained from wood blocks by superposed printing in a manner comparable to that followed in chromolithography although, of course, in the present instance, the blocks are in relief (Fig. 1). From the foregoing account it is obvious that the engraving even of a small illustration, except it be in mere outline, involves a considerable amount of labour; in fact, if the subject were large it was usual to cut it up into areas and distribute between several engravers, the finished blocks finally being joined together to make the block of the whole picture. Hence it is not surprising to find that when the photo-mechanical processes were perfected, the older methods of reproduction were ousted by the newer, more especially since they are much less expensive; these, therefore, may next be considered. THE HALF TONE PROCESS.--For the making of a relief block by photo-mechanical means, the main difficulty is the proper rendition of the tones intermediate between black and white; this has been solved, at any rate in part, by the discovery of the half-tone process.