405 
MISCELLANEA. 
SCIENCE ON THE CONTINENT. 
New Methods of Engraving. — Efforts have been made in all direc- 
tions to supersede the art of the engraver by mechanical and philosophical 
means, and many plans, more or less available, have been adopted or 
published from time to time ; but M. Dulos, member of the Academy of 
Sciences, and engraver to the Imperial Board that has the charge of the 
roads and bridges of France, has recently made public a very ingenious 
system which he has practised for some considerable time. His process, to 
adopt his own words, is based on the following facts : — “ If quicksilver be 
thrown upon a horizontal plate of silver or copper silvered, upon which 
any design has been traced with varnish, the mercury will dispose 
itself on the unvarnished portions of the plate and assume a convex form 
of a certain height. The same, as is well known, will occur when water 
is poured on a plate of ground glass on which a design has been traced 
with any fatty substance. In short, any liquid will act in the same 
manner, when brought into contact after the same fashion with substances 
for which it has different degrees of affinity.” 
The methods employed by M. Dulos are as follows: — For the produc- 
tion of an engraving to be printed by the copper-plate press, he produces 
the writing or design by means of lithographic ink, or chalk, or some other 
similar greasy composition, on a plate of silver or silvered copper ; and 
then he deposits on the plate so prepared a thin coating of copper or iron, 
by the galvanic process, leaving, of course, the design uncovered. The 
ink or chalk is then removed by means of turpentine, and the design 
appears in silver, while the whites or interstices are represented by the 
deposited iron or copper. Mercury is then thrown on the plate and 
attaches itself to the silver only, and the excess being swept from the iron 
by means of a very soft camel-hair pencil, the design itself is represented 
by the convex surface of the mercury. A mould is then carefully taken 
in plaster or melted wax ; the surface of this is metallized and casts taken 
from it, by means of the galvanic pile, which serve as the printing plates. 
For letter-press printing, the design is drawn on a copper plate, and a thin 
coating of silver is deposited on those parts not touched by the drawing 
material ; the latter is then removed either by turpentine or benzine, the 
copper portions thus exposed are oxidized, and the operation is completed 
as before described. An intaglio plate may also be produced by using 
copper for the writing or drawing, depositing thereon a coat of iron, then 
removing the ink or chalk and depositing silver on the exposed copper. 
Another and apparently superior mode of proceeding is to make use of 
