port, near Colebrook Dale, in Shropshire. Establishments have subsequently risen in the city of Worcester, wherein very beautiful specimens are produced; and yet more recently, the manufacture of excellent porcelain has been engrafted upon a long-established pottery for commoner wares, situated at Swinton, near Rotherham, in Yorkshire. At the Rockingham works, which have been so named in compliment to their early patron, the celebrated marquess of Rockingham, porcelain is now produced which vies successfully in every kind of excellence with that of older English establishments. Among many other specimens which attest the proficiency of the Yorkshire manufacturers, two may be more particularly mentioned, which are deserving of more than common attention as denoting the degree of advancement to which the art has reached in England.

One of these pieces is a copy in enamel colours, made on a porcelain tablet, from an original painting by Vandyke, and now in the possession of the noble inhabitant of Wentworth Castle. The subject of the picture is, "The earl of Strafford occupied in dictating his defence to his secretary." The execution of this copy does justice to the masterly original; and, in regard to expression and colouring, has been pronounced equal to the most admired productions of the Sevres works. The other specimen is remarkable not only for elegance of design, and the goodness of the workmanship, but also because it is believed to be the largest piece of porcelain that has hitherto been made in this country. It is a scent-jar, forty-four inches high, made and fired in one entire piece. The base, or plinth, is triangular, having a circular projection at each angle; from these rise lions' paws, upon which the globular body of the jar is supported. The scent is allowed to escape through hexagonal openings in the neck. The jar is divided into three compartments, by as many rustic handles of knotted oak; while branches of the same tree, with their rich foliage rising from the plinth, are spread tastefully over

the lions' paws, and thence entwining with the handles, rise and encircle the base of the neck. The ornaments of the cover are in keeping with those of the jar, it being covered with branches and foliage of the oak: the whole is surmounted by the figure of a rhinoceros. The three compartments into which the jar is divided are enriched with highly finished paintings in enamel colours, executed by one of the proprietors of the works, from designs by Stothard, the subjects of which are drawn from the admirable romance of Cervantes. The circular projections at the base, and the cover, are adorned with paintings from nature, of six subjects of rare botanical plants, the originals of which are in the conservatories of Wentworth Castle. The whole is relieved and enlivened by ornamental work, in burnished and chased gold; and the work, both in its design and execution, is highly honourable to the artists.

Up to a comparatively recent period, the manufacture of earthenwares formed one of the very few branches of domestic industry which were left free from the evil effects of direct taxation, and, except in one branch, of very minor importance, the art is still in the enjoyment of this immunity; to which favourable circumstance may be imputed much of the signal and uniform success whereby it has been attended. In the year 1812, when the duty upon glass bottles was doubled, the manufacturers of these represented to the chancellor of the ex-. chequer, that unless a countervailing tax was levied upon stone bottles, the latter, being wholly unburthened, would possess an unfair advantage, and might be sold at prices that would drive glass bottles out of use. This was a line of argument in no wise unpalateable to the minister, who readily caught at the suggestion of a new object for taxation; and a duty of five shillings on each hundredweight was immediately imposed upon all stone bottles the content of which should be two quarts and under.

The levying of this duty calls for the attendance of revenue officers at all hours on the premises of every

stone-ware manufacturer throughout the kingdom; and it is very much to be doubted whether, in any one year since its first imposition, the expenses of collection have not more than absorbed the whole amount paid by the potters. The total quantity of stone-ware made which is chargeable with the duty does not exceed 600 tons annually, and a large proportion of this is used for purposes to which glass has never been applied. It is not very likely that stone-ware, the utility of which for many purposes is exceedingly great, would ever have been brought into competition with a material so much lighter, and in many respects so much more convenient, even had the pottery continued free from the domiciliary visits of the exciseman; and now that the experiment has been fairly tried during nearly twenty years, and has been found unproductive of any real revenue, there can be no sufficient reason for continuing the impost.

CHAP. II.

GENERAL DESCRIPTION OF INGREDIENTS USED IN THE MANUFACTURE.

DIFFERENT BRANCHES OF THE ART. INGREDIENTS USED. PROPERTIES OF ALUMINA. ITS INFUSIBILITY. CONTRAC

TION WHEN EXPOSED TO HEAT. WEDGWOOD'S PYROMETER.

-COMPOSITION OF GEMS. GREAT ABUNDANCE OF CLAY.PROPERTIES OF SILICA. - ITS GREAT ABUNDANCE. SEA SAND. INCAPABLE OF ARTIFICIAL SOLUTION IN WATER. DISSOLVED NATURALLY. -SPRINGS AT CARLSBAD. BOILING FOUNTAIN IN ICELAND. FUSION OF SILEX.- KINDS OF CLAY USED IN POTTERIES. THEIR VARIOUS MERITS. CHINA MODE OF ITS PREPARATION. -ITS ANALYSIS.-CORNISH FELSPAR. ITS FUSIBILITY.—STEATILE. -EARTH OF BAUDISSERO. ITS ANALYSIS. CORNISH SOPESTONE. -- SPUMA MARIS. -ITS EMPLOYMENT IN PORCELAIN WORKS IN SPAIN.

CLAY OF CORNWALL.

THE art of manufacturing pottery and porcelain naturally divides itself into four different and distinct branches the first of these comprehends a knowledge of the nature and peculiar properties of the various materials, whereof the vessels are composed; the second comprises the methods used in combining these materials, and in fashioning the vessels; the third branch includes the choice and management of the colours and enamels employed in painting and ornamenting the wares, together with the operations necessary for their conversion; and the last division embraces the means required for completing the manufacture by the aid of fire. In describing, however, the different stages of the manufacture as they occur, the painting and baking processes must unavoidably be intermingled.

The chief ingredients employed in the composition of all kinds of pottery are clay and flint: these are both classed by chemists among the primitive earths. The

first of them, in its state of purity, is denominated alumina, or oxide of aluminum; and the latter is called silica, or oxide of silicium. It is only since the year 1754 that alumina has been acknowledged as a peculiar substance; and the period is much more recent when the researches of Davy proved it to belong to the class of metallic oxides.

It is of great importance to make choice of a suitable kind of clay for the manufacture; but, according to the remark of the celebrated Vauquelin, it is much more important to combine this with a due proportion of flint, as good pottery differs from that which is inferior less in the original quality of its elements than in their proportions.

Clay is an opaque and non-crystallised body, of dull fracture, soft enough in all states to take a mark from iron; when breathed on it exhales an odour which, from its peculiarity, takes its name from the material, 、and is termed argillaceous. This is owing to the oxide of iron which is mixed with it, as clay, when absolutely pure, does not emit any odour. Clay forms with water a plastic paste, having considerable tenacity, and which, by the action of heat, is brought to a very great degree of hardness: it is compact, smooth, and almost unctuous to the touch, and when dry, may be easily polished by the finger. It is not soluble in water, but mixes readily with it in all proportions, parting with difficulty from the last portion of that which it has absorbed it will adhere to the tongue. The description of clay employed by potters is infusible in the heat of a porcelain furnace, where some kinds, owing to their being combined with oxide of iron, assume a red colour, while others become of a pure white. The highest temperature to which clay can be exposed tends only to increase its density, hardening its substance and diminishing its volume. This diminution of volume produced by increased temperature is an apparent deviation from the general law of expansion by heat; but the deviation is only apparent,