

HISTORY OF ELECTRO-METALLURGY. 11 



" It was then suffered to remain at rest, when in a few hours I 

 perceived that action had commenced, and that the portion of the 

 copper rendered bare by the scratches had become gradually coated 

 with pure bright deposited metal, whilst all the surrounding portions 

 were not at all acted on. I now saw my former observations rea- 

 lized; but whether the deposition so formed would retain its hold 

 on the plate, and whether it would be of sufficient solidity or strength 

 to bear working if applied to a useful purpose, became questions 

 which I now determined to solve by experiment. It also became a 

 question should I be successful in these two points whether I 

 should be able to produce lines sufficiently in relief to print from. 

 This latter appeared to depend entirely on the nature of the cement 

 or etching-ground I might use. 



" This I endeavoured to solve at once ; and, I may state, it ap- 

 peared at the time to be the main difficulty, as my impression then 

 was, that little less than one-eighth of an inch of relief would be 

 requisite to print from. 



" I now procured a piece of copper, and gave it a coating of a 

 modification of the cement I have already mentioned, and having 

 covered it to about one-eighth of an inch in thickness, I took a steel 

 point and endeavoured to draw lines in the form of net-work, that 

 should entirely penetrate the cement, and leave the surface of the 

 copper exposed. But in this I experienced much difficulty, from 

 the thickness I deemed it .necessary to use; more especially when I 

 came to draw the cross lines of the net -work. The cement being 

 soft, the lines were pushed as it were into each other, and when it 

 was made of harder texture, the intervening squares of the net- 

 work chipped off the surface of the metallic plate. However, those 

 that remained perfect I put in action as before. 



"In the progress of this experiment I discovered that the solidity 

 of the metallic deposition depended entirely on the weakness or in- 

 tensity of the electro-chemical action, which I knew I had in my 

 power to regulate at pleasure, by the thickness of the intervening 

 wall of plaster of Paris, and by the coarseness or fineness of the 

 material. I made three similar experiments, altering the texture 

 and thickness of the plaster each time, by which I ascertained that 

 if the partitions were thin and coarse, the metallic deposition pro- 

 ceeded with great rapidity, but the crystals were friable and easily 

 separated ; on the other hand, if I made them thicker, and of a little 

 finer material, the action was slower, but the metallic deposition was 

 as solid and ductile as copper formed by the usual methods, indeed, 

 when the action was exceedingly slow, I have had a metallic deposi- 

 tion apparently much harder than common sheet copper, but more 

 brittle. 



" There was one most important and, to me, discouraging circum- 



