GE 
_ to the fraud, which may be detected, at least in some 
instances, in the inferiority of the spurious work com- 
pared with that of the master. The beauty of the gem 
should always spe iy with his celebrity ; and, if a 
number should be o under the same name, strong 
suspicions may be entertained whether they be _ge- 
nuine, because ing on hard stones is a tedious 
and difficult art. The principal engravers, for the most 
part, employed themselves only on the finer stones ; 
and therefore the names of these annexed to stones of 
inferior quality render them doubtful, especially if as- 
cribed to the Greeks, or if they are of indifferent exe- 
cution. Greek engravers inscribed their names in their 
own characters, which are borrowed by the Romans 
for the same purpose; and even modern engravers 
have not hesitated to use Greek characters on the 
works from which they themselves expected to gain ce- 
lebrity. ‘The most common deception is the insertion of 
a rated name on a gem, ancient or modern, where 
it is entirely wanting; and the artists most successful 
here were Natter, Pichler also a German, and Sirleti. 
The first of these rather appears to. defend the prac- 
tice ; for he observes, “ Scarcely had I arrived at e 
when the Chevalier Odam engaged me to copy the Ve- 
nus of M. Vettori, and convert it to a Danae, adding 
the name of Aulus. I afterwards sold this production, 
' though a trifle, to M. Shwanav, who was then governor 
of a young prince, and he seemed to prize it highly, 
knowing it to be in my style. I have no hesitation in 
avowing, that I still continue to. make similar copies 
whenever they are commissioned ; but I defy all the 
world to convict me of having sold any one of them as 
an antique.” A gem with a counterfeit name was sold 
in. 1749 for 450 Roman crowns, to a Polish nobleman, 
who presented it as genuine to the Marchioness of 
Luneville.. Precious stones are of unequal value, from 
their faintness or intensity of colour, which has led to 
different methods of improving them. This is gene- 
rally done by heat, which, if applied in a proper degree, 
and sufficiently regulated, has sometimes an admirable 
effect. From the uniform beauty of the ancient corne- 
lians, and the great inequality of the modern, it has been 
there was some method of purifying them, as 
is alluded to by Pliny. The Japanese are said to possess 
ee and it is ery se — e pale 
yellow of a species bearing little value, to a fine glowin 
red. Gems being tran: nt, their colour is affected by 
that of the substance whereon they rest ; and hence the 
variety of foils employed in setting them, which may de- 
ceive an uskilful person. But a more ingenious kind 
of deception is practised, in interposing the thinnest 
possible layer of any colour between two pieces of fine 
rock crystal, which’ counterfeits the real gem. Many 
tules are given for the detection of frauds ; but they 
are of dificult acquisition, and can be learned only by 
practice, 
Independent of these ex 
cient gems, or in improvin 
stones, the imitation of the ke 
ients in counterfeiting an- 
the appearance of 
atter has been carried to a 
very great ere as forming a branch of experimental. 
i eca acquaints us, that Democritus had 
discovered the art of making artificial emeralds ; but, 
in the opinion of Professor Beckmann, this was nothing 
more than giving 
rock crystal. Pliny mentions several artificial stones ; 
and Trebellius Pollio relates, that Gallienus, enraged at 
a deception in selling “ certain glass gems to his wife 
for real jewels,” punished the cheat with castration $ 
and when the byestanders expressed their surprise, he 
ordered the crier to proclaim, imposturam fecit et passus 
M 8. 
est. The difficulty of resenrap.n. + grag in extreme puri« Gema 
a green colour by cementation to. 
127 
ty, was in itself a sufficient guide to colour it in imi- 
tation.; and this art was untionbtediy known from an 
early age. At Alexandria, the glass manufacture was 
in high repute, which is corroborated by an Egyptian 
priest presenting several glass cups, sparkling with 
every colour, to the Emperor Adrian, who valued them 
so metly, that he allowed them to be used only at fes« 
tivals. The coloured glass of this city was ascribed b 
Strabo to a kind of earth found in the ightiodtaole 
Many of the antique fictitious gems, or pastes as we 
more commonly denominate them, are preserved ; and 
the art seems to have been one of the few which was 
not lost during the darker ages. Heraclius, an author 
of the ninth century, gives directions, in uncouth La« 
tin verses, how to imitate ious stones after this 
manner, in a treatise de Artibus Romanorum. We do 
not know what perfection was then attained ; but the 
imitations were so successful, or the people so unskil- 
ful, that coloured glass passed current for the pre~ 
cious original, and donations were unsuspectingly 
made by crowned heads of this as of the most valua~ 
ble substance. A celebrated vase belonging to the ca« 
thedral of Genoa was believed to be a real emerald du- 
ring centuries, and, on a certain emergency, was pled~ 
ged for a. sum equivalent to £30,000 sterling, Natter, 
one of the most skilful modern artists, was long decei« 
ved by a composition in imitation of onyx. The sura 
face was blue, with a black ground, and the whole so 
intimately resembled a natural production, that it was 
not before some accidental circumstance induced him 
to put it to the test, that the truth was ascertained, 
An antique green. paste belonged to the same artist. 
with a white zone in the middle exactly like an onyx,. 
and which did not undergo any alteration from heat. 
The ancients were, besides, acquainted with the art of 
compounding such party coloured pastes of large size, . 
@vhich they are supposed to have accomplished by dip= 
ping a black, blue, or brown lump of glass ina mass 
of milk-white enamel glass, and blowing it into its 
proper form; then the outside being cut away, the fix 
gures required were represented in relief. Mr 
says, that. something of the same kind is at present 
practised in the glasshouses of Bohemia. The art of. 
making fictitious gems was revived and carried to an 
uncommon degree of excellence by ingenious chemists. 
of the seventeenth and: eighteenth century, whereby. 
the most accurate imitation of precious stones, combined 
with antique engraving, has been effected, Neri, Kun-. 
kel, and particularly Orschall, who all flourished in the 
former period, made important improvements ; but the 
two latter seem to have attended more to the imitation. 
of a ruby colour, which was considered most difficult to, 
obtain, and was then the subject of animated ‘controver« 
sies, 
regent of France, and who has left a tract on the subject 
in the Memoirs of the Royal Academy for 1712 ; Lippert 
of Dresden, originally a glazier ; Riffenstein at Rome 3 Dr. 
Quin of Dublin ; James Tassie of Glasgow ;. and a fe. 
male artist, M. Feloix, who of late years carried on the - 
fabrication of artificial gems with great success in Paris, 
To these names must be added thatof M. F ontanieu, 
who, by a numerous series of experiments, has explain- - 
ed an improved method of making pastes for every difs 
ferent species of stone. Tassie perhaps extended the 
art farther than any of the rest; for, availing himself of 
the skill and industry of others, he collected no less than 
15,000 subjects, originals, counterfeits, and im pressions, 
the whole of which he seems to have imitated, This artist - 
ies were succeeded by Homberg, an eminent Modern 
_ chemist, who was patronised by the Duke of Orleans, artists. 
