Diamonds and precious stones, a popular account of gems .. . IOUS STONES. When we examine the marvellous artistic pro-ductions, executed in cameo or intaglio, upon pre-cious stones, we naturally think that the meansemployed must be numerous and complicated, butin reality the apparatus and the tools of the en-graver are as simple as those of the lapidary. Theyconsist of the lathe, and a series of little rods withheads of different shapes, all of which can be ad-justed to the lathe. The lathe, as will be seen from the appendedfigure, is a very simple affair. The axis, driven bythe belt from the
Diamonds and precious stones, a popular account of gems .. . IOUS STONES. When we examine the marvellous artistic pro-ductions, executed in cameo or intaglio, upon pre-cious stones, we naturally think that the meansemployed must be numerous and complicated, butin reality the apparatus and the tools of the en-graver are as simple as those of the lapidary. Theyconsist of the lathe, and a series of little rods withheads of different shapes, all of which can be ad-justed to the lathe. The lathe, as will be seen from the appendedfigure, is a very simple affair. The axis, driven bythe belt from the wheel, is pierced at the centrewith an orifice, into which the tools for cutting thestone are firmly fixed by means of a screw. Theengraver wets the extremity of the mounted rodwith diamond-dust made into a paste with olive-oil, and as the wheel is in motion he applies the ENGRAVING OF PRECIOUS STONES. 283 Stone, properly prepared by the lapidary, and firmlycemented to a piece of reed, to the revolving diamond-dust enables the tool to cut into the. Fig. 123.—The Lathe at work. stone with ease. As the design is frequently veryelaborate and of the greatest delicacy, the tools arenecessarily multiform. Among the different varieties there are four most 284 PRECIOUS STONES. used. The first is hollow; it describes circles withthe utmost facility, and serves, when required, toperforate hard stones. The second is a disk quiteblunt at the edge. The third is a sharp-edged diskof very frequent use, serving as a saw. The fourthis a rod, terminated by a little sphere, and is veryfrequently used. Fig. 124 shows all the tools usedby the engraver. As precious stones suitable for engraving havealways a considerable and sometimes a very highvalue, it is important to be able to make use of everyportion of them. They are therefore sawn insteadof being ground down, so that the portion removedmay also be made use of This operation may beperformed in different ways. The most ancient andsim
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectgems, booksubjectprec
