10 HISTORY OE ELECTRO-METALLURGY. 



ments briefly, not because they are directly connected with what I 

 shall have to lay before the society, but because, by a portion of their 

 results, I was induced to come to the conclusions I have done in the 

 following paper. I was desirous that no action should take place on 

 the wires by which the electrodes were held together; and to 

 attain this object I varnished them with sealing-wax varnish : but, 

 in one instance, I dropt a portion on the copper electrode that was 

 attached. I thought nothing of this circumstance at the moment, 

 but put the experiment in action. 



" This operation was conducted in a glass vessel ; I had conse- 

 quently an opportunity of occasionally examining its progress from 

 the exterior. After the lapse of a few days, metallic crystals had 

 covered the copper electrode, with the exception of that portion which 

 had been spotted with the drops of varnish. I at once saw that I had 

 it in my power to guide the metallic deposition in any shape or form 

 I chose, by a corresponding application of varnish or other non- 

 metallic substance. 



" I had been aware of what every one who uses a sustaining gal- 

 vanic battery with sulphate of copper in solution must know, that 

 the copper plates acquire a coating of copper from the action of 

 the battery ; but I had never thought of applying it to a useful pur- 

 pose, except to multiply the plates of a species of battery, which I did 

 in 1836. My present attempt was with a piece of thin copper plate, 

 having about four inches of superfices, with an equal sized piece of 

 zinc, connected as before by a piece of copper wire. I gave the 

 copper a coating of soft cement, consisting of bees' wax, resin, and 

 a red earth. It was compounded in the manner recommended by 

 Dr. Faraday, in his work on Chemical Manipulation, but with a 

 larger proportion of wax. The plate received its coating while hot. 

 When it was cold, I scratched the initials of my name rudely on the 

 plate, taking special care that the cement was quite removed from the 

 scratches, that the copper might be thoroughly exposed. This was 

 put in action in a cylindrical glass vessel, about half filled with a 

 saturated solution of sulphate of copper. I then took a common gas 

 glass, similar to that used to envelope an argand burner, and filled 

 one end of it with plaster of Paris, to the depth of three-quarters of 

 an inch. Into this I put water, adding a few crystals of sulphate of 

 soda to excite action, the plaster of Paris acting as a partition to 

 separate the fluids, but, at the same time, being sufficiently porous 

 to allow the eloctro-chemical action to permeate its substance. 



" I now bent the wire in such a manner that the zinc end of the 

 arrangement should be in the saline solution, while the copper end, 

 when in its place, should be in the cupreous solution. The gas glass, 

 with the wire, was then placed in the vessel containing the sulphate 

 of copper. 



