252 



NATURE 



[November 6, 1919 



passed into the domain of atomic or molecular 

 physics. We know little enough about gelatine, 

 and want to know a great deal more. Gelatine 

 has proved to be a better medium than collodion, 

 but there seems no reason to suppose that a 

 better than gelatine may not be found. We 

 seem to have realised the maximum aperture (or 



rapidity) in lenses, but there is no such absolute 

 boundary to the sensitiveness of photographic 

 plates, and here we look for continued progress. 

 One fundamental question : Why should silver 

 \ occupy such a unique position among all the 

 ; elements with regard to the sensitiveness of its 

 salts? 



REPRODUCTION OF ILLUSTRATIONS, 1869-1919. 



By Emery Walker. 



FIFTY years ago illustrations for books or 

 periodicals were printed either from en- 

 graved wood blocks, steel plates, or were litho- 

 graphs. In the earliest numbers of Nature 

 examples may be seen of the first method — in that 

 of January 20, 1870, we find a diagram of a sec- 

 tion of the tube by which it was proposed to con- 

 struct the Channel tunnel ; and in that of Feb- 

 ruary 17 an illustration of the Newall telescope at 

 Gateshead : these could scarcely be bettered now. 

 The map illustrating the main drainage of London, 

 in the issue of March 31, is an example of the 

 inadequacy of wood for such a purpose. 



Two years later Mr. Alfred Dawson patented a 

 method of engraving designed to supersede wood, 

 and though his oGject was not attained in subjects 

 requiring tone, diagrams and simple maps were 

 found at once to be better and more cheaply en- 

 graved by his process. 



Dawson's typographic etching, as he named it, 

 is produced thus : A metal plate is coated with a 

 ground of wax composition ; the drawing is made 

 upon the plate through the ground down to the 

 surface of the plate with steel points, similar to 

 those used in etching, but they are faceted to 

 different dimensions at the points. If lettering is 

 wanted, as for a map or a diagram, the letters are 

 stamped in the wax with ordinary printer's type. 

 The spaces between the lines and letters are then 

 raised upon the plate by the addition of melted 

 wax, which unites with the ground and runs up to 

 the line, and in the hands of a skilful operator 

 stops there, thus forming a mould. This is then 

 blackleaded, and upon it copper is deposited by a 

 galvanic battery. When the copper is about the 

 thickness of fairly stout brown paper it is taken 

 off the mould and the outer surface tinned and 

 "backed up " with antimonial lead. The leaden 

 surface is turned in a facing lathe and mounted 

 upon wood or metal, which brings the printing 

 surface of the block to the height of type. It is 

 then practically a piece of type and can be " set 

 up " and printed with the text of the page. 



This process was a development, with some re- 

 finements, of a method patented by Edward Pal- 

 mer about 1840, and called by him " glypho- 

 graphy " ; it was used to a limited extent for book 

 illustration. 



Dawson's typographic etching is still in use, and 



it may be interesting to note that the line blocks 



for the maps in Fortescue's "History of the 



British Army," and the greater part of those for 



NO. 2610, VOL. 104] 



the last edition of the "Encyclopedia Britannica," 

 were engraved in this way. 



In France a method called, after its inventor, 

 " Gillotage " had been in use a few years earlier 

 than this, by which blocks for the cheaper kinds 

 of newspapers were made by transferring to zinc 

 drawings made in reverse upon lithographic trans- 

 fer paper, and the " whites " bitten away with 

 dilute nitric acid. This process was introduced 

 into England after the suppression of the Com- 

 mune in 1871. The application of photography to 

 this process was the beginning of a revolution in 

 book illustration. For though wood-engraving 

 held its own for many years after this for subjects 

 in which chiaroscuro was required, it was gradu- 

 ally disused for drawings made in line, and the art 

 of pen-and-ink drawing for reproduction began. 



Artists soon got used to the new method, and 

 there was a general demand for a process which 

 would reproduce not only drawings in line, but 

 also those made in washes or body colour, and 



i would be suitable for the direct reproduction in 

 the printing press of a photograph from nature. 



I This was met simultaneously by F. E. Ives, an 



i American of great photographic distinction, and 

 by a German inventor, Meisenbach. Ives's pro- 

 cess, though beautiful results vifere obtained, was 

 too complicated for general use, and Meisenbach 's 

 process, called in English "half-tone," held the 

 field. The negative of the drawing to be repro- 

 duced was made by photographing through a 

 screen of parallel lines placed close to, but not 

 touching, the sensitive surface of the photographic 

 plate, and when the exposure was half-completed 

 the lens was covered and the screen turned round 

 so that the lines ran in the opposite direction to 

 that in which the screen was first placed, and the 

 exposure completed. 



This was in 1882. The result was rather crude 

 and deficient in variety of tone. The real ad- 

 vance was made by the invention, by Max Levy, | 

 of Philadelphia, of a new screen composed of two 

 ruled glasses placed in contact at right angles. 

 Max Levy's screens were imported largely, and 



i from this time England, which had been, in the 

 earlier stages of the invention, dependent upon 



: Vienna, and to a smaller extent upon Paris, for 

 half-tone blocks, went ahead, and now half-tone 

 work made here is not second to that of any 

 country in the world. It is used, not only in 

 books, but also for the illustration of daily 

 papers. 



I 



