CHAMBERS'S INFORMATION FOR THE PEOPLE. 



He likewise requires to be exceedingly steady 

 in the hand, for the slightest error would per- 

 haps be irremediable ; therefore, with both his 

 elbows resting on cushions on the bench, and the 

 palm of his left hand leaning on the top of an 

 erect roundish-shaped bolt or pillar, his fingers of 

 both hands are busy in pressing the stone to the 

 edge of the whirling-tool, or guiding it so that it 

 may receive the appropriate indentations. One 

 tool, however, cannot execute all parts of the 

 device. The cutter possesses from one to two 

 hundred tools, usually of soft iron or copper, vary- 

 ing from a large to a small size. It is also neces- 

 sary to explain that the cutting part of each tool is 

 shaped so as to present to the stone a sharp thin 

 edge like the rim of a wheel. (By sticking a small 

 wafer on the point of a pin, and conceiving the 

 edge of the wafer, when turning round, to be the 

 cutting part, a good idea may be obtained of this 

 curious instrument.) As the tool projects horizon- 

 tally, the artist, by holding the stone beneath it, 

 with its surface to be cut uppermost, is thus 

 enabled to watch the progress of his operation 

 from beginning to end. 



Sharp as the cutting-tools of the seal-engraver 

 are, they would entirely fail in perforating the 

 gems to which they are applied by the lathe, 

 unless they were given an additional sharpness by 

 means of a foreign material occasionally applied 

 to them while in rapid motion. This material is 

 usually diamond-dust, or the powder of the ruby 

 and other hard stones. The diamond is so expen- 

 sive an article, that the particles used by the seal- 

 engraver are those which have been rejected as 

 waste by the lapidary. These being placed in a 

 hollow steel tube, having a tight-fitting rammer of 

 the same material, a few smart blows on the upper 

 extremity of the rammer reduce the particles to 

 powder. A small portion of this dust is then 

 mixed with a little olive-oil, and being held to the 

 tool in a state of motion, it is attached to or forced 

 into the metal. If a powerful magnify ing-glass 

 were taken to examine the tool after its absorption 

 of the diamond-dust, its edge would be observed 

 to resemble a rasp or saw, the particles being 

 partly imbedded and fixed in the steel ; hence, 

 properly speaking, it is not the tool, but the 

 diamond-dust upon it, which cuts the surface of 

 the stone. 



To cut an elaborate device, such as a bust or a 

 coat-of-arms, upon the surface of a cornelian or 

 other gem, a vast deal of care is necessary on the 

 part of the artist. The precise depth of every 

 turn and indentation is matter of serious study, 

 and a momentary heedlessness might have the 

 effect of ruining the work of several days. The 

 operator, however, exercises caution in his ingeni- 

 ous labour. The stone being dimmed by friction, 

 is drawn upon with a brass point, to shew the 

 subject, which is of course reversed : the artist 

 first traces the outlines of his figures, next opens 

 them with the bolder tools, and gradually pro- 

 ceeds to the details with finer and finer instru- 

 ments, frequently stopping to take impressions on 

 wax, to see the effect which has been produced, 

 before he gives the finishing stroke to his work- 

 manship ; lastly, the surface is repolished, and the 

 seal completed. 



It will thus be seen that gem-engraving requires 

 not only great ability and skill, but a degree of j 

 patience and perseverance beyond what is required ! 



776 



in most other professions. To cut a metallic seal 

 or die is comparatively an easy task the instru- 

 ments as well as material being thoroughly under 

 the control of the artist ; but to engrave on the 

 hardest gems, whose nature cannot be altered, 

 and which, if destroyed, cannot be replaced to 

 carve the most minute and delicate figures, and 

 to produce them in such a manner as to yield a 

 distinct and smooth impression is altogether an 

 art of the highest order. 



ENGRAVING AND ETCHING ON GLASS. 



The name of cut-glass is given in commerce to 

 glass which is ground and polished in figures with 

 smooth surfaces, appearing as if cut by incisions 

 of a sharp instrument. This operation is chiefly 

 confined to flint-glass (see No. 23), which, being 

 more tough, soft, and brilliant than the other 

 kinds, is more easily worked, and produces speci- 

 mens of greater lustre. An establishment for 

 cutting glass contains a great number of wheels or 

 disks, seldom exceeding a foot in diameter, which 

 are made to revolve with great rapidity by steam or 

 other moving power. Against the circumferences 

 or edges of these revolving wheels, the glass to 

 be ground or figured is held by the hand of the 

 workman. 'The thickness of the cutting-disks, 

 and the forms of their edge, are varied consider- 

 ably ; some being broad, others narrow ; some 

 convex, others concave ; some flat-edged, others 

 wedge-shaped ; and so on, according to the shape 

 of the vessel, and the figures to be produced. 

 Even forty or fifty disks with different shaped 

 edges may be found in the same workshop. 

 Materials of very different degrees of hardness, 

 from cork to wrought-iron, are employed in the 

 formation of these disks. Those made of wrought- 

 iron, which are very thin, are used to cut grooves 

 in glass, by the aid of sand and water, which are 

 caused to drop on the circumference of the disk 

 from hoppers placed above. Cast-iron disks are 

 also sometimes used in the roughest part of the 

 operation ; but the coarse work is usually done by 

 a disk of fine sandstone wetted with water. When 

 ground down to the proper shape, the glass is 

 polished by exposure to softer disks, the action of 

 which is generally assisted by various powders 

 applied in a moist state to the circumference. 

 Thus, a copper disk is used with emery and oil ; 

 a disk of block-tin with peroxide of tin or putty ; a 

 disk of willow-wood with fine pumice-stone, col- 

 cothar, or putty ; and a cork disk having an edge 

 of hat-felt with putty or colcothar.' By such 

 simple instruments is all that variety of design 

 flower, fruit, foliage, arabesque tracery, initials, 

 armorial bearings, &c. produced which now 

 adorns so abundantly the most familiar articles of 

 domestic utility. 



The art of etching on glass is altogether differ- 

 ent, being akin to etching on plates of copper and 

 steel. 'The art,' says Parnell, in his Applied 

 Chemistry, 'may be practised on all kinds of 

 glass ; but the most proper description is good 

 crown-glass. The facts on which this art is 

 founded are, that the vapour of hydrofluoric acid 

 (see No. 21) acts energetically on glass, corroding 

 it as aquafortis does a sheet of copper, and that 

 certain parts of the glass may be easily protected 

 by a varnish, on which the acid exerts no action 

 except at a high temperature. The varnish usually 



