PROFESSOR MIDDLETON ON ANCIENT GEMS.*
"GEM," in common speech, means a precious stone, especially when engraved for an ornament or other purpose. This, putting aside its primary meaning of a "bud," is pretty nearly its significance in classical Latin, though in both languages it might be loosely extended to comprise a pearl. As used by Professor Middleton in this admirable raan6.1, it has of necessity a somewhat wider significance, taking in certain materials other than the many varieties of precious. stones. It includes, for instance, Egyptian scarabs, which are often made out of clay or steatite (a variety of tale), Hittite " gems," for which limestone and marble, among other mate- rials, were used, Phoenician scarabs, and the metal signets. found in the Mycenai tombs. These are curious and interest- ing, and some exhibit delicate workmanship and, occasionally, great artistic skill. Still, the most attractive part of Pro- fessor Middleton's subject is that which is concerned with the- gem proper, and that as it was handled by Greek or Roman artists. Precious stones have always been the most fascinating of human possessions. Their intrinsic beauty goes for something ; their durability for more. The imagination is. fired when we know that the article one touches is exactly the same as it presented itself to human eyes and hands thousands of years ago ; and the feeling is intensified when art has added to the precious material, in the design, the name of the owner, or it may be of the engraver, a distinct human interest.
When we talk of precious stones, however, it must be remembered that the minerals of which the vast majority of the finest antique engraved gems are made are by no means rare or costly. The diamond, for instance, though it occurs. in ancient art, occurs only in. its natural crystal, the art of working it not having been discovered till comparatively recent times. (The " diamond" of the High Priest's breast- plate was possibly a white sapphire.) The minerals used belong in the main to a single species known as quartz, and consisting of silica, the oxide of a non-metallic element called silicon. Of these silicious stones there are numberless: varieties, differing from one another in texture and colour, and through the presence in small quantities of accessory or in- truding materials. Colourless rock-crystal is the fundamental type of the species. Amethyst differs from it only in its colour, which is generally violet, but sometimes citrine, and its curious parquetted structure. Among the translucent varieties of quartz. are the sard, of which Professor Middleton remarks that "it is the most beautiful material commonly used for ancient engraved gems,", a stone amber-coloured, red, or reddish- brown ; the leas translucent cornelia,n (Professor Middleton always calls it carnelian, erroneously, we cannot but think) ; chalcedony, which is milky or bluish, the apple-green chryso- prase, and the leaf-green plasma. Jasper, of which there are many varieties, and which is of very common occurrence, is almost opaque. Another very common stone is the onyx,. which is made up of two or more bands of strata, varying in translucency and hue ; when one of-these strata consists of sard,.
* The TiMpimsed pains Of Classical Times. By. J. Jimmy Middleton. Cambridge The University Prose. 1891. it is called a sardonyx. The sardonyx is peculiarly interesting from its frequent mention in classical writers. Plato speaks of it, though, as Professor Middleton tells us, it does not often occur in Greek gems. The Romans used it, largely, fol- lowing the fashion set by the elder Scipio Africanus. Among non-silicious stones are the cbrysoberyl, the topaz, the emerald, the almandine and other garnets, the peridot, the turquoise, the opal, and the lapis-lazuli (the imprints of Pliny the elder),—and these, from the peridot onwards, are softer than quartz, or even than ancient paste or glass. It must be remembered that, for artistic purposes, the most transparent substances, whatever their intrinsic charms, are not necessarily the most beautiful. It is the translucent stones, such as sard and chalcedony, that are more suitable. Through these, light, but not the forms of objects, can be 'discerned, and so they reveal the charms of fine and noble workmanship more than do the perfectly clear beryl and rock- crystal. In the former, the light passes less regularly—that is, with more scattering of the rays—than is the case with trans- parent stones, and thus the design seems to be illuminated from within. On the other hand, the opaque substances are less suitable for the purpose. Even such stones as the heliotrope and the turquoise, which are capable, when in thin splinters, of transmitting a little light, produce an effect other and more pleasing than do the perfectly opaque materials. Some of the incident light plunges a little way below the surface of the gem, and lights up its superficial layer.
Precious stones, like all other things of value, have been imitated. So we find that many "gems," as it will be still convenient to call them, have been wrought or reproduced in paste and glass. Paste was a hard glass coloured by various metallic oxides, such as those of manganese, iron, copper, and cobalt. Sometimes a piece of paste was treated by the gem- engraver just as if it were a natural stone, and sculptured by the aid of the same tools ; but mare generally the glass was melted and pressed into a mould. Such a mould bad been taken from an engraved gem by a pellet of clay which was afterwards hardened by fire. Paste-gems are often of great beauty in colour and design, though the material lacks some- thing of the optical properties which distinguish not a few of the true natural stones.
The tools and processes enployed in ancient times in en- graving gems aro virtually the same as those in use to-day. The tools were five in number. The drill worked by a bow was the chief, It varied in size, was made of bronze, and acted in virtue of the emery or corundum-powder (mixed with oil) with which its point was smeared. The drill was occa- sionally tubular; in that ease its crown was sometimes set with small crystals of corundum. The second tool was a wire- saw, made effective with the same abrading material. The wheel, or disc of tronze, was similarly employed. A file was also used, not of metal, but of a mixture of emery and resin, heated together, and then allowed to solidify by cooling. The fifth tool was a graver, made by mounting in an iron or bronze handle a crystal or crystalline fragment of diamond or of sapphire, or sometimes a piece of rook-crystal. As a rule, in engraving antique gems, and also those of the einque-cento time, the tool used was worked by the hand, the stone to be -engraved being fixed. In more recent days, the reverse arrange- ment is followed, and in consequence the touch is less free and the style more mechanical. The engraved work and the field of gems were polished by rubbing them with fine powders, hEeinatite, or red oxide of iron, having been generally employed for this purpose.
Paste was often legitimately used, but it naturally suggests the subject of fraud. The ancients were not inexpert in this branch of art, if it may be so called. One might say that the pair of green glass pillara in the temple of the Tyrian Hercules which the priests declared to Herodotus to be emerald, were a gigantic imposture ; but it is not unlikely that the historian deceived himself. Of jewellers' frauds, the chief was the making of a " doublet," a paste backed with a real stone of greater hardness, but poor colour. The two materials were joined by an invisible cement, the line of junction at the girdle of the gem being concealed by the mounting. The alteration and accentuation of the colour of natural stones, particularly of the onyx, by means of various chemicals, is a comparatively 'recent invention ; but the ancients were adepts in the art of changing the original hue by means of strong heat.
Professor Middleton devotes much space to another class of fraud, the modern imitations of ancient gems, imitations some- times so clever that they puzzle even the expert. Again and again we find mention of specimens which it is necessary to leave doubtful. One curious sub-variety of this subject relates to the fraudulent signatures. It is obvious that a signed gem has a special interest. Hence many gems really ancient have had false signatures added to them. Here, again, experts are sometimes at a loss. The famous Carlisle " Mercury" is quoted as a case in point. It bears the name of Dioskourides, and, whether ancient or modern, it is a fine work of art. Un- happily, it once belonged to Baron Stosch, who was in the matter of gems much the same as the notorious Simonides was in the matter of manuscripts.
Professor Middleton completes a singularly interesting book by a descriptive catalogue of the engraved gems in the Fitz- william Museum, illustrated by two plates giving autotype reproductions of some of the principal Roman gems.
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