We can scarcely recognise the appearance of gems, be fore the revival of the art of engraving among the Italians in the fifteenth century. It experienced several fluctua tions during those which succeeded, but was at length com pletely re-established, and several masters have produced works which almost rival those of the ancients. The names of Dominico de Camel, Maria de Pescia, Caradosso, Tag liacarne, Valerio de Vincenti, and more recently Sirleti, who died in the year 1737. This artist claimed his descent from a cardinal of the same name, who had distinguished himself in ecclesiastical affairs ; he was a goldsmith, as well as an engraver on fine stones, and the style of his per formances bears a close analogy to that of the Greeks. Amidst a multitude of subjects, he engraved the Apollo Belvidere, the Farnese Hercules, and the rest of the finest statues preserved at Rome ; but his chef d'oeuvre is esteem ed the groupe of Laocoon on an amethyst. The art has been successfully cultivated in that country, in the most recent times, by Santarelli, Capperoni, Rega, and by a fe male artist, Signora Talani, of great celebrity in Rome. France has produced some good engravers, though the ability which they have displayed has been less permanent than in Italy ; but the best was probably M. Guay, a na tive of Marseilles, who flourished in the middle of the preceding century, and is extolled by Gori as opificum gem niarum decus et ornamentum. He studied first at Paris, next at Florence, and afterwards at Rome, where he pro secuted his profession in imitating the chosen productions of the ancients. After returning to his native country, he was appointed engraver of fine stones to the king ; and with his decease the art is considered to have expired in France, until restored under the patronage of the National Institute, in awarding a premium to M. Jeuffroy in 1810. There are very few, if any, of the arts in which the Ger mans have not excelled ; indeed, they seem to stand pre eminent among the moderns for mechanical ingenuity. Yet their first engraver on gems, Henry Enghelhart, was only a eotemporary of Albert Durer. One of the best was Lau rence Natter, a native of Biberach in Suabia, who followed the profession of a jeweller both there and in S itzerlatid ; then travelling through Italy, he established himself at Ve nice, devoting his attention exclusively to engraving gems. After visiting England, lie repaired to Denmark and St Petersburg. In Denmark he engraved several of the royal family, dspecially the Princess Royal, whom he represent ed on an oval black and white onyx, three inches long, and in relief so prominent, that the head projected about half an inch from the stone. Ile next engraved an elephant, for one of the royal orders, also in relief, on an oriental jas per, which being of different colours, enabled him to make the elephant and a man mounted on it white, the tower red dish on its back, and the feet of the animal darker, while the ground of the whole was a fine deep green. Natter was treated with particular regard by the King, Christian VI. who assigned him an apartment in his palace, and be stowed upon him valuable presents when he departed for England, where he died in the year 1763. Natter was the author of a treatise on gems, wherein he draws a compari son between the works of the ancients and the moderns, and lays down the principles of the practical part of the art. It has been erroneously maintained, that he is the only author who does so ; but in a treatise by M. Marlette, a few years anterior, it is discussed still more at large : Both these works are extremely useful to the artist and antiquarian.
Modern gems, by common consent, are judged inferior to those of antiquity, and hence many attempts have been made to substitute fictitious gems for those which are real. This is accomplished by two or three different methods : the improvement of a stone, which is really precious,—the imposition of an absolute counterfeit of it,—or the insertion of the name of an ancient engraver on a production of mo dern origin. This last expedient is by no means uncom mon; and some of the most reputable engravers are accus ed of lending their assistance to the fraud, which may be detected, at least in some instances, in the inferiority of the spurious work compared with that of the master. The beauty of the gem should always correspond with his cele brity ; and, if a number should be offered undeD the same name, strong suspicions may be entertained whether they be genuine, because engraving 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 ascribed to the Greeks, or if they are of indifferent execution. 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 celebrity. The most common deception is the insertion of a celebrated 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 practice ; for he observes," Scarcely had I arrived at Rome when the Chevalier Odam engaged me to copy the Venus of M. Vettori, and convert it to a Danae, adding the name of Aldus. I afterwards sold this production, though a tri fle, 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 com missioned ; but I defy all the world to convict me of hav ing 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 ge nerally done by heat, which, if applied in a proper degree, and sufficiently regulated, has sometimes an admirable ef fect. From the uniform beauty of the ancient cornelians, and the great inequality of the modern, it has been sus pected there was some .method of purifying them, as is al
luded to by Pliny. The Japanese are said to possess the secret ; and it is common elsewhere to raise the pale yel low of a species bearing little value, to a fine glowing red. Gems being transparent, their colour is affected by that of the substance whereon they rest; and hence the variety of foils employed in setting them, which may deceive an un skilful 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 rules are given for the detection of frauds ; but they are of difficult acquisition, and can be learned only by practice.
Independent of these expedients in counterfeiting ancient gems, or in improving the appearance of hard stones, the imitation of the latter has been carried to a very great ex tent, as forming a branch of experimental chemistry. Se neca acquaints us, that Democritus had discovered the art of making artificial emeralds; but, in the opinion of Pro fesso• Beckmann, this was nothing more than giving a green colour by cementation to rock crystal. Pliny men tions several artificial stones ; and Trebellius Pollio re lates, 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 ex pressed tbeir surprise, he ordered the crier to proclaim, inoosturanz.fecit et nassus est. The difficulty of obtain ing glass in extreme purity, was in itself a sufficient guide to colour it in imitation ; and this art was undoubtedly known from an early age. At Alexandria, the glass ma nufacture 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 highly, that he allowed them to be used only at festivals. The coloured glass of this city was ascribed by Strabo to a kind of earth found in the neighbourhood. Many of the antique fictitious gems, or pastes as we more commonly denominate them, arc preserved ; and the art seems to have been one of the few which was not lost du ring the darker ages. Heraclius, an author of the ninth century, gives directions, in uncouth Latin verses, how to imitate precious stories after this manner, in a treatise de Romanorum. We do not know what perfection was then attained ; but the imitations were so successful, or the people so unskilful, that coloured glass passed cur rent for the precious original, and donations were unsus pectingly made by crowned heads of this as of the most va luable substance. A celebrated vase belonging to the ca thedral of Genoa was believed to be a real emerald during centuries, and, on a certain emergency, was pledged for a sum equivalent to 30,000/. sterling. Natter, one of the most skilful modern artists, was long deceived by a com position in imitation of onyx. The surface 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, which they are supposed to have accomplished by dipping. a black, blue, o: brown lump of glass in a mass of milk-white enamel glass, and blowing it into its proper form; then the outside being cut away, the figures requir ed were represented in relief. Mr Raspe says, that some thing of the same kind is at present practised in the glass houses of Bohemia. The art of making fictitious gems was revived and carried to an uncommon degree of excel lence by ingenious chemists of the seventeenth and eigh teenth century, whereby the most accurate imitation of precious stones, combined with antique engraving, has been effected. Neri, Kunkel, 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 consi dered most difficult to obtain, and was then the subject of animated controversies. They were succeeded by Horn berg, an eminent chemist, who was patronised by the Duke of Or leans, 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 ; Dr Quin of Dublin ; James Tassie of Glasgow ; and a female 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 that of M. Fon tanieu, who, by a numerous series of experiments, has ex plained an improved method of making pastes for every different 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 impressions, the whole of which he seems to have imitated. This artist was born in Scotland, and practised modelling and sculpture in M0) 1111 during three years preceding 1766. He then repaired to London, where, amidst the study of various branches of the fine arts, he confined himself principally to the com position of coloured pastes and artificial gems. The for mer were first brought into repute by the London jewel lers employing them for ornamental purposes; the latter consisted of a beautiful hard white enamel, which struck fire with steel, and was not affected by heat. Tassie car ried on an extensive traffic in these fictitious gems, which he sold from eighteen pence to two guineas, according to the quality ; and the late empress of Russia, a liberal pa tron of the arts, commissioned a complete set of his whole collection. This he executed in a masterly manner, imi tating original gems where circumstances admitted of it, where otherwise the pastes were chiefly transparent; and cabinets containing them are now in the imperial palace of Czarsko Celo. As public fashions are fluctuating, pastes began to lose their value, and fictitious engraved gems are at present in little repute in Britain, though imita tions of precious stones are still worn as personal orna ments.