= 
~ deposited copper, as well as the rapi 
160 =e . Electrography. + . oo 
— —— be 
witha brush, the mould being previously warmed slightly, so-that — 
the wax may be more evenly distributed. The wire connecting 
the mould with the zinc, must be soldered to the back of the lead- 
en impress. No sooner are the poles of this small battery con- 
nected and placed in their respective solutions, than the posit 
of metallic copper commences on the mould, copying with in- 
conceivable delicacy, all the most minute lines and even the 
shades of polish which may be on the face of the matrix. Great 
care is necessary to see that the surface to be deposited upon, is 
clean and bright, for the least grease or foreign matter, even such — 
as would come from the fingers, will prove an impediment to the 
uniformity and beauty of the result. From one day to three days 
are necessary, to obtain a copy of a medal or of any object of similar 
size, according to the required thickness of the deposit. During 
this time, the apparatus should be placed in a situation where the 
temperature can be maintained at about 100° or 120°, and the 
saturation of the cupreous solution should be carefully insured, by 
suspending in it a gauze bag containing crystals of the salt, which 
will be dissolved as the strength of the solution declines. If this 
latter precaution be neglected, the free acid resulting from the 
constant decomposition of the sulphate of copper will interfere 
materially with the success of the rs and the tenacity of the 
y with which the process 
proceeds seems to depend in some measure, on the temperature 
being moderately elevated. 
After the deposit has gained sufficient thickness, it may be e 
sily removed by immersing the united metals in boiling wate! or 
better by holding the matrix for a moment over a spirit lamp, o 
if large and heavy, over a chaffeur of burning coals, when 
different expansibility of the two metals will cause an instant sepa- 
ration, with asmart crackling sound. The separation of the depos 
it, where it has fallen on a matrix of copper, is not however, 80° 
sy, but it may generally be effected witliout serious difficulty, if 
previously to placing the matrix in the solution, its warmed surface 
be slightly covered with fine bees’ wax, which must then be re- 
moved with great care from all parts of it, while still warm, rub- 
bing it briskly with a clean fine cloth, all the wax seems to be" 
moved, but in fact, a film remains which is sufficient 10 prevent 
chemical union between the surfaces, although if carefully don® 
not interfering with the deposition of the metal. The casts th 
