PROCESS OF ENGRAVING UPON SILVER. 251 
ART. LITl.— ON A NEW PROCESS OF ENGRAVING UPOK 
SILVER, SILVERED OR GILT COPPER, INVENTED BY 
M. POITEVIN. 
By M. Becquerel. 
M. NiEPCE DE St. Victor has discovered a very in- 
genious method of copying drawings and engravings upon 
paper, glass or plates of metal. M. Poitevin has converted 
these copies into plates engraved in relief and intoglio, after 
the manner of copperplate engravings, so that any number 
of proofs may be taken of them. Two or three hours suf- 
fice for the operation. 
The eng;raving or manuscript to be copied is first exposed 
to vapour of iodine, which is deposited solely upon the 
black portions : the iodized ensraving is then pressed 
gently upon a plate of silver or silvered copper, polished in 
the same way as for Daguerreotypes. The black parts of 
the engraving, which have received the iodin.e, transfer it to 
silver, the corresponding parts of which are converted into 
iodide. The plate, connected with the negative pole of a 
battery consisting of a few pairs, is then immersed for some 
minutes, in a saturated solution of sulphate of copper, 
which is connected with the positive pole by means of a 
strip of platinum. The copper is deposited only on those 
parts which are not covered with iodide, and which con- 
sequently correspond to the white portions. We thus ob- 
tain a perfect representation of the engraving, in which the 
copper represents the white, and the iodized silver the black 
parts. The plate must only remain a very short time in the 
bath of sulphate of copper ; for if the operation were con- 
tinued too long, the entire plate would become coated with 
copper. 
The plate, after having received the deposit of copper, is 
very carefully washed, and then immersed in a solution of 
