6 Correction of Engraved plates hy Mectro-deposition. [Ja]!T, 



is poured into the trough and any air bubbles that may appear in the cuts 

 are gently removed with a clean camel-hair brush. A piece of clean sheet- 

 copper, large enough to entirely cover the parts to be filled in, and attached 

 to the copper pole of the battery by a copper band previously soldered to 

 it, is laid down above them at a distance of about half an inch, being 

 supported in position by wax pellets or pieces of wood fastened to the 

 plate with a little wax. The circuit being thus completed, the deposition 

 of copper in the cuts commences and fills them up completely in the course 

 of 18 to 24 hours. To ascertain whether the deposit is sufficient, a little 

 instrument like a fork with three prongs of equal length, is used ; the centre 

 prong being placed in the cuts the other prongs should be quite clear of the 

 plate on both sides. When the deposit is sufficiently thick, the battery is 

 disconnected, the copper solution poured back into its bottle, the wax wall 

 removed, the Brunswick black cleaned otf with turpentine, and the superfluous 

 deposit is removed exactly as in M. G-eorge's system by filing it down with a 

 bent flat file, the plate being protected meanwhile by a mask of stout paper 

 fastened down with Brunswick black. After filing to within the thickness 

 of the paper, the remaining deposit is carefully scraped off till the even surface 

 of the plate is restored. As the success of the operations entirely depends 

 on the perfect adherence of the deposited copper to the original plate, every 

 precaution must be taken to avoid the presence in the cuts of the slightest 

 trace of grease or other matter which might cause non-adherence. The 

 cutting tools must be quite clean and the cuts sliould be made with clean 

 square edges. The sooner the filling in is performed after the erasures have 

 been made the better. When the cuts are a day or two old, and in all cases 

 where any doubt as to the perfect cleanliness of their surface exists, M. 

 George recommends that the metal should be slightly bitten by means of a 

 Bunsen battery, but I have found that the acid solution of sulphate of 

 copper eflectually removes all tarnish and oxidation, if not too old. 



My practical acquaintance with the subject of electro-metallurgy and 

 the experience we have yet had in working the method are too limited to 

 enable me to state positively the advantages of the system I have adopted 

 over those practised in Europe, but it has already been applied with complete 

 success in the correction of two very valuable plates, and seems likely to 

 prove of great service when extensive corrections have to be made. It is 

 quite as simple as M. George's method and appears to possess the advan- 

 tage of securing a more regular deposit over an extensive surface of the 

 plate, the only precaution necessary being, to proportion the size of the 

 anode to the extent of the work to be performed, so that the whole of the 

 erasures are covered by it. In this respect it appears equal to the Vienna 

 method but is much more rapid and economical in operation, though it loses 

 the advantage of the protection aff'orded to the engraved plate by the 



