Barrow, John [Editor]
Dictionarium Polygraphicum: Or, The Whole Body of Arts Regularly Digested: Illustrated with Fifty-six Copper-Plates. In Two Volumes (Band 2) — London, 1758

Page: 334
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the edges muff, be fcumbled into the grounds by fine ftrokes; fo
they muft not feem cut or feparated from the reft.

There are ftill others of different colours ; and fuch as are, a
it were, black on the infide, are to be coloured and finifhed wit
indigo, as well as the feed.

If the Tulips have a yellow ground, ufe gamboge ; and, to fi
nifli them, add a little umber or biftre.

The leaves and ftalks of Tulips are commonly painted with ;
fea-green, and fhaded and finifhed with an iris green, with broai
ftrokes along the leaves.

Some again may be coloured with verditer, mixed with ma-
fHcote; thefe you may fhade with bladder green, that they may
have a more yellowim caft.

TURCOISE, 1 is a precious ftone of a blue colour, ordi

TXJRQUOIS, i narily opaque, but fometimes a little tranf-
parent.

There are of thefe feveral kinds, oriental and occidental; o
the new rock and of the old.

The oriental Turcoife partakes more of the blue tincture than
the green ; and the occidental more of the green than the blue

Thofe of the old rock are of a deep blue, and thofe of the new
rock more whitifh, and do not keep their colour.

The oriental ones come from Perfia, the Indies, and fome
parts of Turky ; and fome even fuppofe it is thence they take
the modern name of Turcoifes.

The occidental are found in various parts of Europe, particu-
larly Germany, Bohemia, Silefia, Spain, and France.

Turcoifes all grow of a round or oval figure ; they cut eafily,
and feals are frequently engraven on them.

The Turcoife is eafily counterfeited, and that fo perfectly,
that it is impoffible to difcover the deceit without taking it out of
the collet.

In the memoirs of the Academy of Sciences, we have a very
curious account of the formation of the Turcois, the manner of
giving it the blue colour, &c, by M. Reaumur.

He obferves, that the Turcoife is one of the fofteft of precious
ftones, its hardnefs fcarce exceeding that of a cryftal, or a tranf-
parent pebble; though fome are much harder than others, and
ftill the harder, caeteris paribus, the more valuable, by reafon of
the vivacity of the polifh, which is always proportionable to the
hardnefs.

Rofnel, a jeweller, eflimating the feveral precious ftones, fet a
hard Turcoife, whofe blue is neither bright nor deep, on the
foot of the moft perfect emeralds, that is, on a level with a dia-
mond. Thofe that have any defect: he only values at a French
ciown a. carat. »

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