SC.
In one of the upper rooms of the Electrical Exhibition in Paris, there
is an interesting collection of plates and proofs produced by various
methods of photo-engraving, invented by M. Henri Garnier, whose name
is so well known in connection with these processes, and whose
beautiful plate of the Chateau of Maintenon gained for him a gold
medal at the Paris International Exhibition of 1867.
Some interesting details of these processes are given in an extract
from a report on them by M. Davanne to the Societe d'Encouragement
pour l'Industrie Nationale, read at its sitting on the 22d July last,
of which copies are distributed gratis in the exhibition.
The report opens with a brief allusion to M. Garnier's continuous
labors in permanent photographic printing, commencing with the
ingenious mercury process worked out in conjunction with M. Salmon,
and published in 1855, in which a print which has been exposed to the
fumes of iodine is laid down on a plate of polished brass, so that the
iodine, absorbed by the printed lines, slightly attacks the brass;
mercury being then rubbed over the brass, forms an amalgam with the
iodized parts. If a roller charged with printing ink be now passed
over the plate, the ink will only be taken on the pure brass, and not
on the iodized parts.
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