C 47S ] 



On the 'Electro-type? — By Charles Huffnagle, Esq. 



REFERENCES TO THE PLATE. 



1. Wooden cell. 



2. Glass cylinder. 



3. Brass binding-screw. 



4. Shelf perforated in the 

 centre. 



5. Copper plate, on which coin is 

 placed. 



6. Zinc plate on acid lfjuid. 



7. Crystals of sulphate of copper to 



keep up a saturated solution. 



My Dear Torrens, — I felt gratified, at our last meeting, to find you 

 were also much pleased with the fac-simile of my coin of ' Alexander ' by 

 the Voltatype, and I cheerfully promised at your desire an account of the 

 process, for which, and also for the successful result of the experiment, 

 I am indebted to my talented friend Professor O'Shaughnessy. I believe 

 detailed accounts have already appeared in print, but this mode of copy- 

 ing coins and medals is so exceedingly simple — the result so surprising 

 and satisfactory, and it is so fully in the power of every body disposed to 

 devote the slightest attention to it — that we cannot make it too widely 

 known. 



1st. You must provide yourself with a wooden cell 8 or 10 inches 

 square — with an inside coating of sealing wax — or other cement to ren- 

 der it water tight. This box should be 3 inches deep, with a ledge 1 inch 

 from the top to support a wooden shelf. 



Affix to the edge of the box a brass binding-piece, formed of square 

 brass, perforated with two holes and furnished with binding-screws. 



2d. A glass cylinder open at both ends, to the lower end of which a 

 piece of moist bladder must be secured with a waxed cord, and the diameter 

 of this cylinder must correspond with the perforation in the shelf fitted 

 to the square box. 



3rd. Plates of sheet zinc amalgamated by mercury ; i. e., by rubbing a 

 few globules of mercury over the zinc, after dipping it into a mixture of 

 one part of sulphuric acid and one of water, must also be provided ; and 

 these plates corresponding in length and breadth to the size of the cylin- 

 der, must be attached to a copper wire 6 or 8 inches long. 



4th. A plate of copper 3 or 4 inches square with a copper wire 6 inches 

 long. 



5th. Supplies of sulphate of copper in crystals, and concentrated sul- 

 phuric acid. 



When you proceed to use the apparatus, prepare a saturated solution of 

 the blue salt, in soft hot water, strain it off turbid and allow it to cool— 



