» 
«i ee ae ; r" ‘ , ee ee. sa 
oy & ‘ * — Pd «* 
Electrography. eg — . * 
The wood-engraver can now furnish blocks which will admit 
_ of much greater delicacy ‘of finish, although it is doubtful if any = * 
material can endure the common press for a longer time than well. Q" 
. Ptepared wood is stated to have done. But the ease and accuracy 
with which the most elaborate designs may be multiplied, will . 
give this mode the preference. ° ” 
The question very naturally arises, to what metals is this pro- % 
cess applicable? We believe we are warranted by the present — 
state of our knowledge, in stating that it has hitherto been applied 
successfully to copper alone, although no reasonable doubt can be 
entertained that modes will yet be discovered by which it can be 
profitably used with other metals. Platinum has been thus pre- 
cipitated from its chloride, not in a useful form, but in the state 
of minute division, in a black powder, resembling spongy plati- 
num, ‘This result is the more to be regretted, since we are in 
great need of new and economical modes of working this invalu- 
able metal. Gold and silver may be also thrown down from their 
respective chloride, and nitrate; but the film deposited is very 
thin, and may be removed by rubbing with the finger, and 
ceases to be deposited when the surface on which it is produced 
is entirely covered. We were indeed informed, a few months 
since, that M. De La R re had furnished the artists of Geneva 
With a modification of this process, whereby they were able to 
gild spoons and other articles of silver successfully. But we un- 
derstand that more was expected from it than has been realized. 
Lead may be treated in this way, but it is so readily worked in 
other modes, that it presents no object. , 
We have observed in numerous experiments on this subject, 
that not only the thickness of the porous diaphragm, but also the 
hature of its surface, influences the rapidity and character of the 
deposited copper. Thus in using a plaster division, formed in. 
astone pot, as shewn in fig. 2, by casting between two boards, 
the surfaces of the division became perpendicularly striated by the 
Stain of the wood, and by little prominences on the lower end, 
as left by the saw, These strie were apparent on the deposit, 
_ giving it the appearance which metals receive from the rolling 
cylinder—and they were very bold when the copper had attained 
the thickness of a dollar. Calf-skin gave no such result; on 
the contrary, the surfaces of deposits obtained with that sub- 
Stance as a division were quite smooth. Bladder-skin, undressed, 
Causes the deposit to be pitted with little hollows and correspond- 
