ENGRAVING on Precious Stones is the representing of figures or devices, in relief, or indented, on various kinds of hard polished stones.
This art is at least as ancient as the time of Moses. From the Book of Exodus (xxviii. 9) we learn that he was commanded to take two onyx stones and engrave on them the names of the children of Israel, according to their birth, with the work of an engraver on stone, like the engravings of a signet. From this passage we may conclude that the Israelites had acquired a knowledge of the practice of gem and seal engraving, as well as of other arts, during their captivity in Egypt.
In the Book of Exodus (xxxv. 32) we learn that Bezaleel, the son of Uri, "had knowledge in all manner of workmanship, to devise curious works in gold, and in silver, and in brass, and in the cutting of stones to set them; and with him was Aholab, an engraver and a cunning workman."
The art of engraving on precious stones is one of those in which the ancients excelled; there being various antique agates, cornelians, and onyxes, which surpass anything of the kind which the moderns have produced. Pyrgoteles among the Greeks, and Dioscorides under the first emperors of Rome, are the most eminent engravers we read of. The former was so esteemed by Alexander, that he forbade anybody else to engrave his head; and Augustus's head, engraved by the latter, was deemed so beautiful that the succeeding emperors chose it for their seal. The extravagant passion of the Roman matrons for engraved gems was satirized by Juvenal, and Pliny remarks that they "loaded their fingers with princely fortunes;" but these costly ornaments were not limited to the person;—this extravagant gradually extended to the wearing apparel of both sexes, and to other articles, and the dress of the wealthy Romans sometimes absolutely glittered with engraved gems.
All the polite arts having been buried under the ruins of the Roman empire, that of engraving on stones met with the same fate. It was retrieved in Italy at the beginning of the fifteenth century, when one John of Florence, and after him Dominic of Milan, performed works of this kind no way to be despised. From that time sculptures of this kind became common enough in Europe, and particularly in Germany, whence great numbers were sent into other countries; but they fell far short of the beauty of those of the ancients, especially those executed on precious stones; for, as to those on crystal, the Germans, and after them the French, &c., have succeeded well enough.
In this branch of engraving artists make use either of the diamond or of emery.
The diamond, which is the hardest of all stones, is only cut by itself, or with its own matter. The first thing to be done in this branch of engraving is, to cement two rough diamonds to the ends of two sticks large enough to hold them steady in the hand, and to rub or grind them against each other till they be brought to the form desired. The dust or powder which is rubbed off serves afterwards to polish them; and this is performed with a kind of mill that turns a wheel of soft iron. The diamond is fixed in a brass
dish, and, being thus applied to the wheel, it is covered with diamond dust, mixed with oil of olives; and when the diamond is to be cut facet-wise, first one face, and then another, is applied to the wheel. Rubies, sapphires, and topazes, are cut and formed in the same way on a copper wheel, and polished with tripoli diluted in water. As to agates, amethysts, emeralds, hya inths, garnets, rubies, and others of the softer stones, they are cut on a leaden wheel, moistened with emery and water, and polished with tripoli on a pewter wheel. Lapis-lazuli, opal, and some others, are polished on a wooden wheel. To fashion and engrave vases of agate, crystal, lapis-lazuli, or the like, a kind of lathe, like that used by pewterers, is made use of to hold the vessels, which are to be wrought with proper tools. That of the engraver generally holds the tools, which are turned by a wheel; and the vessel is held to them to be cut and engraved, either in relief or otherwise—the tools being moistened from time to time with diamond dust and oil, or at least emery and water. To engrave figures or devices on any of these stones when polished, such as medals, seals, and the like, a little iron wheel is used, the ends of whose axis are received within two pieces of iron, placed upright, as in the turner's lathe, and so adjusted as to be brought closer, or set further apart, at pleasure. At one end of the axis are fitted the proper tools, which are kept tight by a screw. Lastly, the wheel is turned by the foot, and the stone applied by the hand to the tool.
The tools are generally of iron, and sometimes of brass. They vary in form, but generally bear some resemblance to chisels, gouges, and the like. Some have small round heads like buttons; others are like ferrets, to take the pieces out; and others again are flat. When the stone has been engraved, it is polished on a hair brush-wheel with tripoli.
For engraving on stone, see LITHOGRAPHY. (W. H. L.)
ENGOULEE, in Heraldry, a term applied to crosses, saltires, &c., when their extremities enter the mouths of beasts, as lions, leopards, &c.