The practical requirements of the Mesopotamians were satisfied with a hasty impression from their seals, but we must be more difficult to please. Before we can study the cylinder with any completeness we must have an impression in which no detail of the intaglio is omitted; such a proof is to be obtained by a complete turn of the cylinder upon some very plastic material, such as modelling-wax, or fine and carefully mixed plaster-of-Paris. The operation requires considerable skill. When it is well performed it results in a minute bas-relief, a flat projection, in reverse, of the whole intaglio. The subject represented and its execution can be much better seen in a proof like this than on the original object, it is therefore by the help of such impressions that cylinders are always studied; we make use of them throughout this work. Our Figs. 136 and 137 give some idea of the change in appearance between a cylinder and its impression.
The cutting on the cylinders, or rather on all the engraved stones of western Asia, is in intaglio. This is the earliest form of engraving upon pietra-dura in every country; the cameo is always a much later production; it is only to be found in the last stage of development, when tools and processes have been carried to perfection. It is much easier to scratch the stone and then to add with the point some definition to the figure thus obtained, than to cut away the greater part of the surface and leave the design in relief. The latter process would have been especially difficult when the inscriptions borne by many of the seals came to be dealt with. What long and painful labour it would have required to thus detach the slender lines of the cuneiform characters from the ground! And why should any attempt of the kind be made? As soon as these engraved stones began to be used as seals, there was every reason why the ancient process should be retained. The designs and characters impressed upon deeds and other writings were clearer and more legible in relief than in intaglio. And it must be remembered that with the exception of some late bricks on which letters are raised by wooden stamps, the wedges were always hollowed out. We find but one period in the history of Chaldæa when, as under the early dynasties of Egypt, her written characters were chiselled in relief. It is, then, apparent that the artists of Chaldæa would have done violence to their own convictions and departed from long established habits, had they deserted intaglio for work in relief. That they did not do so, even when their skill was at its highest point, need cause us no surprise.
The Chaldæans naturally began with the softest materials, such as wood, bone, and the shells picked up on the shores of the Persian Gulf. Fragments of some large pearl oysters and of the Tridacna squamosa, on which flowers, leaves, and horses have been engraved with the point, have been brought from lower Chaldæa to London (see Fig. 138).[301] Limestone, black, white, and veined marble, and the steatite of which most of the cylinders are made, were not much more difficult. These substances may easily be cut with a sharp flint, or with metal tools either pointed or chisel-shaped. With a little more effort and patience still harder materials, such as porphyry and basalt; or the ferruginous marbles—serpentine, syenite, hematite—could be overcome. The oldest cylinders of all, those that are attributed to the first Chaldæan monarchy, are mostly of these stubborn materials; their execution was easy enough to the men who produced the statues of Gudea.[302] All that such men required to pass from the carving of life-size figures to the cutting of gems was good eyesight and smaller tools.
It was only towards the end of this period that more unkindly stones began to be used, such as jasper and the different kinds of agate, onyx, chalcedony, rock-crystal, garnets, &c. The employment of such materials implies that of the characteristic processes of gem-cutting, whose peculiarity consists in the substitution of friction for cutting, in the supercession of a pointed or edged tool by a powder taken from a substance harder, or at least as hard, as the one to be operated upon. “The modern engraver upon precious stones,” says M. Soldi, “sets about his work in this fashion. He begins by building up a wax model of his proposed design upon slate. He then takes the stone to be engraved, and fixes it in the end of a small wooden staff. This done he makes use, for the actual engraving, of a kind of lathe, consisting of a small steel wheel which is set in motion by a large cast-iron flywheel turned by the foot. To the little wheel are attached small tools of soft iron, some ending in a rounded button, others in a cutting edge. The craftsman holds the staff with the stone in his left hand; he brings it into contact with the instrument in the lathe, while, from time to time, he drops a mixture of olive oil and diamond dust upon it with his right hand; with the help of this powder the instrument grinds out all the required hollows one after the other.”[303]
Fig. 138.—Engraved shell. British Museum.
The first engravers who attacked precious stones had no diamond dust. They supplied its place with emery powder, which was to be found in unlimited quantities in the islands of the Archipelago, whence it was imported by the Phœnicians at a very early date. Moreover there was nothing to prevent them crushing the precious stones belonging to the class called corundum, such as sapphires, rubies, amethysts, emeralds, and the oriental topaz. No doubt the lathe or wheel was a comparatively late invention. M. Soldi thinks it hardly came into use in Mesopotamia till about the eighth century B.C. Before that the continuous rotary movement that was so necessary for the satisfactory conduct of the operation was obtained by other means. According to M. Soldi they must have employed for many centuries a hand-drill turned by a bow, like that of a modern centre-bit or wimble.[304]
Fig. 139.—Chalcedony cylinder. British Museum.
