A moderate quantity of yellow tripoli is placed on flannel slightly moistened with oil, and applied just like glass paper, the motion of the lathe being occasionally changed in direction, and sometimes stopped, whilst the flannel is rubbed lengthways, to diversify the direction of the friction thus applied. It is desirable not to use a second supply of tripoli, unless at an early stage, but to allow the powder to become embedded in the flannel, and worn down to a smooth face, on which account but little oil should be used. The tripoli then becomes gradually finer and drier, and with careful management will produce a surface entirely free from scratches and highly polished, without the adventitious aid of lacker; this mode produces a far more durable surface, wood being a much harder substance than the shell lac, the basis of the varnish for hardwood. 5. - Hardwoods Polished with Dutch Rush. - A dozen or more short pieces or joints of the rush just divested of the knots and tied up at the ends as a faggot are used with water, applying all sides of the rush to wear it down smooth alike; and in this case, as in the last, the same polisher is continually used throughout the process, in order that it may become finer with the progress of the polishing. After a sufficient period, and when the rush feels inactive, it is laid by and allowed to dry, when it is again used in the dry state, and serves to bring up a polish nearly or quite equal to that produced by the tripoli. Some artizans employ subsequently to the rush, putty-powder or rottenstone, but this is only admissible when the surface of the wood is so smooth and dark as to be incapable of retaining the powders in its pores, or of becoming stained by them. 6. - Turned Works Carved and Ornamented with the eccentric chuck, or revolving cutters, etc, do not admit of any polishing beyond the use of a clean dry brush; sometimes a drop of oil is placed on the brush, but the oil although it may leave a temporary gloss, is eventually absorbed in the wood, and renders the surface more dull than before.

Occasionally the ornamented works are coated slightly with thin varnish laid on with a brush, this is not to be recommended, and unless the patterns are very bold, and the varnish is very dexterously applied, it is almost certain to fill in the hollows to a degree that is highly prejudicial to the appearance of the work.

That sharp tools and proper treatment completely obviate the necessity of any polish on engine turned works in hardwood, beyond that of a dry brush, is abundantly proved by several of the most tasteful and finished specimens ever executed, which were the work of a lady, and are in the author's possession. The proper course was pursued in their formation; namely, that of polishing very highly the facets forming the cutting edges of the tools, in the manner that is elsewhere explained, and allowing the tool to cut gradually, or without plunging it too rapidly or too rankly into the work.

Flat Works.

7. - Flat Works in Wood. - The majority of the joiners' works wrought with the plane, and others executed with the file, come under this denomination. Their flat surfaces are in general scraped with the ordinary joiner's scraper, a thin plate of sheet steel, the edge of which is sharpened on the oil-stone and burred up with the burnisher. {See page 484, vol. ii., fig 331.) Afterwards the wood is cleaned with glass paper, of two or more sizes, wrapped around a flat piece of cork glued on a block of wood about 3 x 4 inches square, or on a piece of wood on the flat surface of which one thickness of woollen cloth is stretched and nailed around the edges which acts with greater accuracy than the elastic cork, and keeps the work flatter.

8. - Small Flat Works in Wood are often rubbed upon the sheet of glass paper, which is then laid on the flat bench or other board - a practice analogous to that pursued by watchmakers and others. In some cases also small flat surfaces in wood are finished on face wheels, or plane disks of wood on which glass paper is glued; this practice is somewhat common for the mechanism of piano-fortes, and many years back an analogous method was pursued by Mr. Larkin, which is described under the head Flint.

9. - Polished Flat Works. - It may be generally said that the several modes of polishing, already described in reference to turned works of wood, are all more or lest practised also in flat works; indeed, they were always used until comparatively of late years, when the so-called French polish, (to be hereafter spoken of,) has nearly obtained a monopoly in the embellishment of furniture and other works; the carved surfaces of which are still, however, mostly varnished with a brush as in painting, and not by attrition. But the old fashioned polish due to linseed oil, applied daily for a year or two, although tedious, produced an equally beautiful and far more lasting polish, although it must be admitted the oil has the effect of rendering the woods somewhat darker. In conclusion of these remarks the reader is referred to the article Marquetry in this Catalogue.

WROUGHT IRON

WROUGHT IRON. - The parts of machinery made of wrought iron are polished as described in the general article Machinery in this Catalogue: two other examples are alone here given. The parts of stoves and similar works in wrought iron, are sometimes ground, but in general they are filed, draw-filed, rubbed with an emery rubber, and burnished with the two handed burnisher having a stirrup for the foot; as in such works the glittering polish on a comparatively scratchy surface, is considered to be good enough for the purpose. Round knobs, crooked arms, bows of keys, stirrups, bridle bits, and pieces free from sharp angles, are often polished by wrapping once or twice around them, a piece of soft rope or string smeared with the polishing stuff; and by using a sawing motion with the two hands, a considerable friction is applied all around the objects. The screws of corkscrews are mostly thus dressed.

ZINC

ZINC. - Door plates made of rolled zinc are cut out, scraped to a clean surface, hammered flat and then planished, after which they are by some workmen smoothed, 1st, with a stick of blue stone and water; 2ndly, with emery paper wrapped on a piece of wood or cork, and moistened with oil; 3rdly, with rottenstone and oil on a coil of list.

Other workmen employ immediately after the scraper, 1st, pumice-stone, either in the lump or powder; 2ndly, flour emery and oil on a flat woollen rubber; and 3rdly, rottenstone in the same manner.

Zincographic Plates for Printing. - In order to give these the fine grained surface required in this branch of the graphic art, they are, 1st, rubbed with ordinary sand, and 2ndly, with fine sifted sand, the rubber is of list rolled up tight and used with water; the zinc plate is then ready to receive the drawing which is made with the ordinary lithographic chalk upon the plate, or is transferred from the transfer paper and fixed by an acid preparation.

Zinc plates are equally susceptible with lithographic stones of the transfer process, and which by Wood's patent method of "Anastatic Printing," may be employed in producing fac-simile copies, by transfer, of engravings or books of the very earliest dates in their respective arts.

ZIRCON

ZIRCON is the generic name of three varieties of gems known as the Hyacinth, the Jargoon, and the Zirconite, they are sometimes so hard as to require to be cut into facets with diamond powder the same as Sapphires. "The exposure of some varieties to heat, deprives them of their colour, and they are said to have been sold in that state in place of the diamond."