= : - < 
Electrography. = 159 
rie : * 
_ ‘its position and thickness may be regulated at pleasure, by two 
boards fitting the sides of the vessel and leaving the desired space 
between them; after the plaster has become firm, the boards may 
be withdrawn. Any of the substances before named will answer 
to form this division. C, D, the two chambers formed by the divis- 
ion B, 6. -Kither of these may be devoted to the cupreous solu- 
tion, and the other to the saline or acid water. 'The connecting 
wire will then form an arch between the two, supported by a strip 
of wood laid over the division. Mr. Joseph Saxton, of the Uni- 
ted States Mint, showed us one of these little pots which had been 
sawn dow a stone-cutter’s saw, in the line B, 6, and into the 
slit so formed, a piece of calf-skin was inserted and the joint se- 
cured from leakage by a hoop of iron, fitted with a binding screw.* 
These two forms of apparatus will be found quite sufficient to 
copy most objects of art except large engraved plates, which must 
be provided with a box suited to their form and dimensions.t 
Being provided with such an apparatus as has been described, 
the next question is, how to make use of it in copying any ob- 
ject of art; to accomplish this, the experimenter must proceed 
ous 
as follows :—First, of metallic medals. A concave copy of the - 
medal must be first obtai either by fusible metal, or by im- 
pressing it on soft and sheet lead, in a press of sufficient 
power to strike up its most lelicate lines boldly. This prelimi- 
hary step is not indispensable, because the object to be copied 
may be at once immersed in the cupreous solution, and a deposit 
obtained on it, which must subsequently be removed, and used 
asa mould, in which to cast the relief; but it is obvious that 
twice the time is required in this way, to obtain the final copy, 
beside the danger of injuring the beauty of the medal by solder- 
Ing the connection on it, however adroitly that operation may be 
performed : and the deposited copper is much more difficult to re- 
move from a bed of the same metal, particularly if the matrix 
Was itself the result of Voltaic casting. But in whatever manner 
the intaglio copy may have been obtained, before immersing it in 
the cupreous solution, all those parts of the surface not intended 
to be copied, must be covered with bees’ wax or varnish, applied 
PV aan Se é a 
Re Mr. Saxton has by this mode, copied a Daguerreotype plate ; the picture being 
“isible by the difference of polish in the deposit. his is the strongest proof of 
the great delicacy of this process which has come to our knowledge. 
1 See Mr. Spencer's book, p. 47, for a good form of apparatus for this purpose. 
* 
