total rejection of lead is not compatible with perfection in pottery.

The blue-printed pottery is a very popular kind, and most persons who have seen it placed near the preceding, must have remarked that it is of a finer kind, with a very different tint or colour.

The best species is in considerable demand for dinner, dessert, tea, and supper services; while its cheapness has caused it to supersede almost every kind of ware.

The difference is caused by two peculiarities; one in the clay, arising from the employment of a greater proportion of blue and porcelain clays and flints; the other in the glaze, from certain components being mixed together, and calcined into a frit, which is often picked and sifted, then ground together with glass and white lead, and mixed with certain proportions of Cornish-stone and fliut.

One kind of this pottery has its glaze varied to capacitate it for enamelling. The blue printed tea-ware has recently obtained the name of semi-china, owing to its being, when well fired, very fine, white and neat, and possessing some degree of transparency.

The chalky pottery is a very excellent and beautiful kind, having a delicate white appearance, of fine texture, and glassy smoothness. The nature of the clay and the glaze renders it very proper for enamelling, as smalts are introduced, in accordance with the views of the maker, to effect the tints.

The clay is boiled on a plaster-kiln, and consists of certain proportions of porcelain, blue and Welsh clays, pulverized, calcined, or raw flints, Cornish-stone, white enamel, tinged with smalts; and some persons add calcined bone and plaster of Paris. This ware requires a most ardent fire for the biscuit. The glaze is composed of a frit of glass, Cornish-stone, flint, borax, nitre, red-lead, potash, Lynn sand, soda, and cobalt calx. After fritting, and being well fired, it is ground and mixed together with white-lead, glass, flint, and Cornish

stone.

The fine red pottery is formed of almost equal proportions of yellow brick-clay and the red from Bradwall-wood; an inferior sort is made for lustre-ware.

In the Hall-field colliery, east side of Henley, is found a niarl, which, when properly prepared, by levigating and drying, will alone form a very beautiful light red, of four distinct shades, according to the intensity of the firing. This was discovered by Mr. G. Jones, in 1814, who commenced a manufacture of this kind of ornamental pottery for Messrs. Burnett,

to be shipped to Holland; but the sudden return of Napoleon from Elba so disconcerted the arrangements, that the elder Mr. Burnett died suddenly, and Jones did not long survive the disappointment he experienced.

The introduction of ochre will change the red to a brown colour.

The bamboo, or cane-coloured pottery, is a very beautiful kind, employed chiefly for ornamental articles, and the larger vessels of tea-services. It is never glazed outside, though one kind has the outside vitrified. The insides of tea-ware are well washed with a liquid which forms, when fired, a thin coating of glass. The colour varies from that of a light bamboo to almost a buff: but the prevalent colour is nankeen. The best clay or body is formed of proportions of black marl, brown clay, Cornish-stone, and shavings of cream-coloured pottery.

The jasper pottery was invented by Mr. J. Wedgwood. It is extremely beautiful; and is formed of blue and porcelain clay, Cornish-stone, Cork-stone, (sulphate of barytes,) flint, and a little gypsum, tinged with cobalt calx.

The pearl pottery is a superb kind for elegant and tasteful ornaments, and is so much valued, that the workmen are usually locked up, and employed only on choice articles. The components of the clay are blue and porcelain clay, Cornishstone, a little glass, and red-lead. This forms the best body for apothecaries' mortars; but it is more expensive, and more durable, than the common mortar body.

The black Egyptian pottery is now so very popular for tea-services, that few persons are ignorant of what is meant by this denomination. Its components are cream-coloured slip, manganese, and ochre; sometimes glazed with lead, Cornishstone, and flint; and the inside is washed with white-lead, flint, and manganese. It was the custom formerly to grease the outside with butter or suet, to give it a bright appearance. The ochreous material is obtained from the water that is pumped out of the collieries. This water is carried along channels in which are placed small weirs, to afford an opportunity for the precipitation of the sediment. When a sufficient quantity has accumulated, the water is diverted, the weirs are emptied, and the thick fluid is thrown into small pools, called sun-pans, whence the moisture is evaporated by the solar heat. This substance is afterwards burned with smallcoal, which renders it proper for use.

The unpleasantness of the grease, requisite to give brightness to the black, having been a subject of general complaint,

Messrs. Riley, of Burslem, were induced to attempt to remedy it; the result of which was, the invention of a new black porcelain, with a bright burnished, vitrescent appearance, superior to any other kind of dry-body pottery. It never imbibes dust, or absorbs moisture; and it can be cleaned with water equally as well as the finest porcelain, and always retains the appearance of a beautiful black coral.

The drab pottery is useful for articles which require strength to be united to ornament, as flower-pots, water-jugs, &c. It is formed of blue, porcelain, and Bradwall-wood clays, Cornish-stone, and black marl, mixed with nickel; one kind is made of turners' shavings of cream-coloured ware made into slip, and mixed with nickel. The inside is rendered white by a wash of slip, flint, and porcelain clay.

It has for some time been usual for ladies of taste and acquirements in the fine arts, to purchase porcelain in its glazed state, for the exercise of their talents and ingenuity in ornamenting their own tea-services. This very pleasing amusement is often aided by manufacturers, who readily afford every assistance in their power to facilitate the easy enamelling of such services; they supply proper mineral colours, and the rectified oil of amber, for the best purposes, and the best oil of turpentine for others; and they attend to the proper firing of the enamel, burnish the gold, and dress

off the whole for the table.

The different combinations of materials appear to be of less importance in the fabrication of good pottery, than due regard to well-determined proportions. All clays have some proportions, more or less, of metallic matter, which cause great difference in their appearance, and the effects produced on them by fire. All clays vary in colouring according to the ardency of the fire; hence the oven-man's greatest care is, to place the saggars in the most appropriate parts.

The chief ingredients are clay and flint; for no pottery will be perfect unless made of suitable clay, with a definite proportion of flint. The great difficulty is to unite beauty and goodness in the same composition. If too much flint be used, the pottery, after being fired, will crack on exposure to the air; and if too little, the glaze will not be retained on it after firing. Every kind of clay that is dried alone will crack; for if pure argillaceous earth be made sufficiently soft to be wrought on the potter's wheel, it will, while drying, shrink one inch in twelve, which will inevitably cause it to craze.

Pure clay (alumina) is always opaque, and the flint (silica) always transparent; but both are prepared previously to

being used. Alumina will unite with silica in the humid way, and form a paste, which, when dry, will resist decomposition by atmospheric affection.

Experienced manufacturers know that they can easily compound clays which will fire very white, be beautifully semi-transparent for porcelain, and bear to be covered with a shining glaze; but they will prove deficient in tenacity for working, want proper compactness and density, break by. sudden applications of heat and cold, and the glaze, because too soft, will crack, become rough, and lose its lustre. Again, they compound clays which have suitable tenacity for working, become very hard and dense without fusing by being fired, sustain, uninjured, sudden changes of excess of temperature, and are yet deficient in the requisite whiteness, fineness of texture, beauty, and transparency. Some clays of this description are manufactured.

Having proceeded thus far, the reader may feel surprised that we have not accompanied our observations with recipes for the manufacture of the several kinds of pottery, as is customary in works of this description; but these, we can assure him, are, as far as we have seen, erroneous; and, indeed, the manufacturers are so very silent upon this head, that the exact proportions of the components of bodies, glazes, and colours, cannot easily be obtained. We shall therefore conclude this article by stating, that the district called "the Potteries," is an extensive tract of country in the hundred of North Pyrehill and county of Stafford, comprehending an area of about eight miles long, and six broad; and that the principal towns and hamlets contained within the limits of the Pottery are Stoke, Henley, Shelton, Golden-hill, Newfield, Smith-field, Tunstall, Long-port, Burslem, Cobridge, Etruria, Lune-End, Lower Lune, and Lune-Delft.

HOROLOGY

In the early ages, time was measured either by the sundial or clepsydra; in the former, by the shadow of a wire, or of the upper edge of a plane, erected perpendicularly on the dial, falling upon certain lines meant to indicate the hour; in the latter, by the escape of water from a vessel through a small orifice, which vessel had certain marks upon it to show the time the vessel was discharging.

These modes are now superseded by the use of clocks, watches, and chronometers, which indicate time by the more ment of machinery.

Under this general head of Horology, therefore, we propose to treat of the structure of the several kinds of machines now used for the exact measurement of time; in doing which, the article will of necessity be divided into three sub-heads, Clocks, Watches, and Chronometers; and to them will be annexed two others, treating of some of the best kinds of pendulums and escapements.

CLOCKS.

CLOCKS are certain machines, constructed in such a manner, and so regulated by the uniform action of a pendulum, as to measure time, in larger or smaller portions, with great exact

ness

Fig. 489 represents the profile of a clock. P is a weight suspended by a rope that winds about the cylinder or barrel C, which is fixed upon the axis aa; the pivots bb go into holes made in the plates TS, TS, in which they turn freely. These plates are made of brass or iron, and are connected by means of four pillars ZZ, and the whole together is called the frame.

The weight P, if not restrained, would necessarily turn the barrel C with an uniformly accelerated motion, in the same manner as if the weight were falling freely from a height; but the barrel is furnished with a ratchet-whee K K, the right sides of whose teeth strike against the click, which is fixed with a screw to the wheel D D, as represented in fig. 490, so that the action of the weight is communicated to the wheel DD, the teeth of which act upon the teeth of the small wheel d, which turns upon the pivots e c. The communication or action of one wheel with another is called the pitching; a small wheel like d is called a pinion, and its teeth the leaves of the pinion. Several things are requisite to form a good pitching, the advantages of which are obvious in all machinery where teeth and pinions are employed. The teeth and pinion-leaves should be of a proper shape, and perfectly equal among themselves; the size also of the pinion should be of a just proportion to the wheel acting upon it; and its place must be at a certain distance from the wheel, beyond or within which it will make a bad pitching.

The wheel E E is fixed upon the axis of the pinion d; and the motion communicated to the wheel DD by the weight is transmitted to the pinion