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matrix, and a print is then obtained al- 
most similar to the piece engraved in 
wooed. Sometimes it is necessary to 
touch it with the graver, and it is then | 
fixed on a little square table.” 
The second article is in the fourth 
volume of the Encyclopedia, published 
m 1780. ‘ With respect to pieces of a 
larger dimension, (says this article) it wali 
be requisite to get, and to prepare 
spath, to beat or pound it very fine, to 
moisten it with a solution of sal-am- 
moniac, and then to press it into a form 
or frame. The engraved piece is laid and 
foreibly held in it; it is then drawn igi 
the mass of spath i is suffered to dry, and 
the melted metal is poured upon it. The 
form is then gently shaken, that the me- 
tal may penetrate into all the crevices ; 
and the print which the metal yields, 
when it is cooled, will only want to be 
slightly touched with the graver.” 
Dareet, a member of the National 
Institute, published in the “ Journal de 
Medecine” (for June, 1773), some ex- 
periments relative to certain mioectailic 
mixtures, which have this property, that 
they are subject to grow soft, and even 
to melt, and to run in boiling water. 
Darcet ‘does not lay claim to the merit 
ef these discoveries, in the first instance. 
He attributes the honour of them to New- 
ton, to Homberg, and to Muschenbreck ; 
but to their observ ations, he added new 
experiments ‘and positive results. ‘These 
results are amony others, 1. That sixteen 
parts of bismuth, four of pewter, three 
of lead, make a composition or mixture, 
which turns very soft in boiling water, 
and which congeals like an amalgama, 
when half cold. 2. That eight parts of 
this bismuth, five parts of lead, and three 
of pewter, make a mixture which melts 
before the water comes to boiling. The 
effect is the same, whether in large or 
in small masses. 
In general, the same metals have more 
ar less hardness and fusibility, according 
to the preparations, or to the mixed sube 
stances that are applied to them. Of a 
pare metal, it has been remarked, that it 
is softer than amixed metal. Pure metal 
receives the impressions better, but does 
not keep them so well. Metal, beaten 
cold, is harder then that which has been 
Proceedings of Learned Societies. 
[June 1, 
annealed. Lead and tin melt more readily, 
when they are in a state of combination, 
than when separate. 
The author then introduces, (from a 
Memoir by Rochon), an experiment of 
the late Dr, Franklin, made in America, 
to perform printing as rapidly as writing. 
This method consisted in writing on pa- 
per with ink stiffened with gum. The 
writing was sprinkled with sand, or grains 
of cast iron, sifted or pulverized, and then 
inclosed between two boards, or plates. 
One of these two flat surfaces which is to 
receive the engraving, should be of wood, 
or of a soft metal, such as pewter or 
copper; the other may be of hard stone, 
or of iron. These two plates, submitted 
to the action of a press, will force the 
writing into the softer metal. The 
The.wooden or metal surface will then 
yield a copy of the writing, and the plate, 
according to the method used by the 
engravers, will serve to give as many 
copies as the depth of the engraving will 
allow. 
Rochon remarks, that the copies ob- 
tained by this process, are not beautiful to 
the eye; and he had recourse to a me= 
thod which was.not lable to the same 
objection. This is to write with a steel 
point on a copper plate, varnished ac- 
cording to the methed of the engravers. 
The plate is covered with aqua fortis; 
and the letters that are formed, when the 
varnish is taken off, with the ‘point that 
has been used’ for writing, will be 
found engraved, and copies may be taken 
from them. It is true that these 
copies are inverted, but counter- 
copies may be taken off :on - the spot, 
which read in the right direction. 
Thus, for example, twelve copies may 
be taken off, and while the ink is 
yet fresh, let a blank leaf, wetted and, 
prepared, be put hetween each, and then 
with a single act of the press, twelve 
counter, or secondary copies will be ob- 
tained very neat, and very legible. _ 
Rochon concludes, by saying, that this 
method will never become equal to that 
of engraving; but that it will be found 
very useful in all cases, where it may be 
necessary to produce a rapid multiplica- 
tion of copies. 
(To be concluded in our next. ) 
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