628 Mr. J, Wilson Swan [May 20, 



kindness of Messrs. Elkington, has been prepared for me, this is 

 connected with the negative pole of a battery — and here is a plate of 

 copper, connected with the positive pole. When I immerse the mould 

 in the solution — at about two inches- from the copper plate — the 

 electrical circuit is completed, and the same electrolytic action that 

 the experiment illustrated will take place. Copper will be deposited 

 on the mould, and will be dissolved in equal quantity from the copper 

 plate, and the supply of copper in the solution will thus be kept up. 

 As it will take a little time to obtain the result I wish to show, I 

 will put this aside for ten minutes or so, and proceed to speak of 

 different applications of this principle of copper deposition. 



For the reproduction of fine works of art in metal, electrotype is 

 unapproachable. The extreme minuteness with which every touch 

 of graver or modelling-tool is copied by the deposited metal film, 

 separates electrotype by a wide space from all other modes of casting. 

 Even the Daguerreotype image is not too exquisitely fine, for electro- 

 type to copy it so perfectly, that the picture is almost as vivid in the 

 cast as in the original. 



It is this quality that has given to electrotype a role which no 

 other process can fill, and, so far, its practical utility is not greatly 

 dependent on the cost of the current. This applies to all those most 

 beautiful things here and in the Library, lent by Messrs. Elkington. 

 These could all have been produced commercially even if there 

 had been nothing better for the generation of the current than 

 Smee's battery ; a very good battery, by the way, for small operations 

 in copper deposition. It gives a very low electro-motive force, 

 and that is a defect, but in copper deposition, the half volt or 

 so is generally sufficient to produce, automatically, the required 

 current density. 



One of the uses of electrotype, not greatly affected by the cost of 

 deposition, is that of the multiplication of printing surfaces. In 

 these days of illustrated periodicals, electrotype has come more and 

 more into use for making duplicate blocks from wood engravings, 

 which would soon be worn out and useless if printed from direct. It 

 is also employed to make casts from set-up type, to be used instead 

 of ordinary stereotype casts, when long numbers of a book have to be 

 printed ; also as a means of copying engraved copper-plates. Here 

 are examples of all these uses of the electrotype process. The electro- 

 blocks are lent by Messrs. Kichardson & Co., and the copper-plates 

 by the Director General of the Ordnance Survey Office, Southampton. 



The plates illustrate the method employed at Southampton in the 

 map printing department. The original plates are not printed from, 

 except to take proofs. The published maps are all printed from 

 electrotypes. Here is an original plate — here the matrix, or first 

 electro,* with, of course, all the lines raised, which are sunk in the 

 original. The second electro is, like the original, an intaglio. Here 

 is a print from it, and here one from the original plate. Practically 

 they are indistinguishable from each other, and bear eloquent testi- 



