306 On Electrotyping Operations of the U. 8. Coast Survey. 
to make castings of a finer kind than were obtained by melting 
and pouring. Propositions to this effect are about all that can be 
attributed to the rival claimants for the invention of electro-met- 
allurgy ; for neither the English nor Russian philosopher revealed 
what had not been known before. 
Yet to Jacobi and Spencer is due the merit of having called 
public attention to the subject; for in doing this, they have con- 
ferred benefits on the world greater, perhaps, than by making 
an original discovery. 
After the publications of Jacobi and of Spencer had called the 
attention of the scientific world to the new art, the principles in- 
volved in it became the study of several eminent philosophers, 
who disclosed the methods to be followed for obtaining reguline 
metal. After this, several departments of electro-metallurgy 
rapidly advanced. Electro-plating, and the multiplication of 
pages of letter-press work, as pages of type, and wood-cuts, (elec- 
tro-stereoty ping, ) were soon extensively practised ; but the copy- 
ing of the delicate touches of the copper-plate engraver (the 
electrotype proper) was beset with difficulties. On account of 
the great value of the engraved plate, together with the risk of 
its being detroyed in the attempt to copy it, and the uncertainty 
as to whether the duplicate would have good metallic properties, 
even if the operator should have the good fortune to obtain one, 
this department of the art, (the first and most beautiful of Spen- 
cer’s suggestions,) was allowed to rest as an experiment or 
confined to articles of small size and value. 
Adhesion of deposite to matriz.—Electro-metallurgy requires 
that the deposited metal should have all its cohesive properties. 
If such a deposit of copper is made on a clean plate of copper 
it is obvious that the deposited metal will cohere with the plate 
on which it is made, and an elaborately engraved plate would 
thus be converted into a mere mass of metal. The electroty, 
art, therefore, cannot exist before means are provided for prevel 
ing this destructive adhesion. 
Various plans for overcoming this difficulty have been proposed. 
All these, however, have a common feature, which is to prevent 
the deposit and matrix from touching by means of an interven 
ing film of heterogeneous matter. 
_ Mr. Smee proposes to use that coating of air which adheres 8 
firmly to polished metals, (so strikingly exhibited when the at- 
. 
tempt is made to wet a polished knife-blade.) To obtain = 
air coating, he directs that, after every attachment has been mace 
hi ao rea it be placed in a cool and moist cellar for a few days 
introducing it into the electrotype vat. oe 
moke, black lead, oils, and powders, and wax, have also been 
proposed for covering the face of the plate. 
