MECHANICS AND USEFUL ARTS. 69 







from 1>lork plates, the printing lines of which stand up like those of a wood- 

 cut. This is accomplished by printing the picture, with prepared ink, upon a 

 metal plate; the plate is then subjected to voltaic action, which cats away 

 the metal, excepting those parts protected by the ink. Where it is required 

 to make a reduced copy of a drawing, the process is inverted; that is, the 

 vulcanized India-rubber sheet is stretched in the frame before the impression 

 is made upon it. It must be evident that, on its being allowed to contract 

 to its original size, ifc will bear a reduced picture upon its surface, from which 

 the copies are printed. 



The application of this art to map-work is very apparent. Let us instance 

 the ordnance maps. Both enlargements and reductions of the original scale 

 on which they were drawn have been made in the ordinary way at an enor- 

 mous expense, the greater part of which might have been avoided had this 

 process been known. As it is, we have gone to work in a most expensive 

 manner. The survc} 7 for the whole of England was made on the very small 

 scale of one inch to the mile for the country, and of six inches to the mile 

 for towns, and now there is a cry for an enlarged scale of twenty-five inches 

 to the mile. In other countries, comparatively speaking, poor to England, 

 this scale has been far exceeded. For instance, even poverty-stricken Spain 

 is mapped on the enormous scale of as many as sixty-three inches to the 

 mile. 



But with this question we have nothing to do; our purpose is only to 

 show that it would be a great saving if the twenty-five inch scale had been 

 originally carried out, as with this new process all the smaller scales could 

 have been produced with perfect accuracy from this one at a very small 

 cost. , 



Indeed, the public could, if they wish, have pocket fac-simile copies of 

 that gigantic map of England and Scotland on the twenty-five inch scale, 

 which, according to Sir M. Peto, would be larger than the London Docks, 

 and would require the use of a ladder to examine even a county. The new 

 art is applicable to engravings of every kind; and, moreover, it can very 

 profitably reproduce type itself in an enlarged or reduced form. This is a 

 fact of great importance to all Bible societies; for enormous sums are spent 

 in producing this work in all imaginable sizes. But, it will be askecl, what 

 advantage does this method present over a resetting of the page in the usual 

 manner? Two very important ones speed and price. Let us suppose, for 

 instance, that we wish to make a reduction of a royal octavo University Bible 

 to a demy octavo. The price of resetting the type alone would be 800, 

 and the "reading for corrections" another 300 at the least. Now, an 

 identical copy could be produced by the process employed by the Company 

 for 1'20; there would be no charge for " reading," as the copy is a fac-simile. 

 Where there are many rules, marginal notes, and different kinds of types, 

 as in Polyglott Bibles, the advantage of reproducing by the India-rubber 

 process would be, of course, proportionately greater. 



We may mention another power possessed by the new method, which 

 will prove very valuable to publishers. It sometimes happens that when a 

 new edition of a work .is called for, some of the original blocks, or stereo- 

 typed impressions, are found to be wanting. Heretofore new drawings and 

 engravings would have to be made; but now, all this difficulty is obviated 

 by simply taking the engraved page out of the old book, and reproducing 

 the block required from it. This actually occurred with respect to the well- 

 known work "Bell on the Hand," the missing blocks of which have been 



