The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates — Birmingham, [ca. 1785]

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1 cm

the faid water upon it. The pearls will, by decrees,
diffolve, and at lad turn to a clear calx, much like
diffolved hlver calx ; pour off the mercurial water;
boil the calx well out and dry it ; then put it into
a clean crucible by ttfelf; and melt and caft it into
what form you pleafe. When cold, polifh it in the
fame manner as you do gems or crvfcals. and you
wdl have your work of the confiilencv and beauty
of the fined and cleared oriental pearl.

Choice fecrets imitating precious ftones, or for
making artificial gems:—This curious art is arrived
to that perfection, that it is capable of imitating pre-
cious ftones in their luftre, colour and beautv, even
to furpafs the natural ones, except m hardnefs, which
to obtain, has been, and no doubt lull are, the en-
deavours of feveral increnious men.

The art of making artificial gems, confifts chiefly
in rightly imitating the teints of thofe that are real ;
thele muff be extracted from fuch things as refift the
fire, and do not change their colour, though of a
volatile nature : thus verdigreafe being put into the
fire, is changed to another colour, but when put in
fulion with cryftal, it retains its natural colour.

You muft therefore take fuch colours as change
not, when mixed together; therefore fince blue and
yellow make a green, you muft take fuch blue as
will not hurt the yellow when you mix them, and al-
fo fuch a yellow as fhalt not be detrimental to the
•blue, and fo of the other colours. We fhall give
very plain and certain inftruftions to carry the in-
genious artift with cafe and pieaiure through this
labour, and fir It (hew him —

To make a fair emerald :—Take of natural cryf-
tal lour ounces., vctdiiirife fortv-eisdit grains; crocus

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