an appellation given to things of a destructive or poisonous nature. See Poison.

DELFt, a town of the united provinces, and capital of Delftland in Holland. It is a pretty large place, very clean and well built, with canals in the streets, planted on each side with trees. The public buildings, especially the town-house, are very magnificent. Here are two churches: in one is the tomb of the prince of Orange, who was assassinated; and in the other, that of admiral Tromp. It has a fine arsenal, well furnished; is about two miles in circumference, and is defended against inundations by three dams or dikes. Here is made a prodigious quantity of fine earthenware called delft-ware; but the town has no other trade. It is pleasantly situated among the meadows on the river Shie, in E. Long. 4. 13. N. Lat. 32. 6.

Delft-Ware, a kind of pottery of baked earth, covered with an enamel or white glazing, which gives it the appearance and neatness of porcelain.—Some kinds of this enamelled pottery differ much from others, either in their sustaining sudden heat without breaking, or in the beauty and regularity of their forms, of their enamel, and of the painting with which they are ornamented. In general, the fine and beautiful enamelled potteries, which approach the nearest to porcelain in external appearance, are at the same time those which least resist a brisk fire. Again, those which sustain a sudden heat, are coarse, and resemble common pottery.

The basis of this pottery is clay, which is to be mixed, when too fat, with such a quantity of sand, that the earth shall preserve enough of its ductility to be worked, moulded, and turned easily; and yet that its neatness shall be sufficiently taken from it, that it may not crack or shrink too much in drying or in baking. Vessels formed of this earth must be dried very gently to avoid cracking. They are then to be placed in a furnace to receive a slight baking, which is only meant to give them a certain consistence or hardness. And, lastly, they are to be covered with an enamel or glazing; which is done, by putting upon the vessels thus prepared, the enamel, which has been ground very fine, and diluted with water.

As vessels on which the enamel is applied are but slightly baked, they readily imbibe the water in which the enamel is suspended, and a layer of this enamel adheres to their surface; these vessels may then be painted with colours composed of metallic calcareous earths, mixed and ground with a fusible glass. When they are become perfectly dry, they are to be placed in the furnace, included in cases of baked earth called teggares, and exposed to a heat capable of fusing uniformly the enamel which covers them.—This heat given to fuse the enamel being much stronger than that which was applied at first to give some consistence to the ware, is also the heat necessary to complete the baking of it. The furnace and the colours used for painting this ware, are the same as those employed for Porcelain. The glazing, which is nothing but white enamel, ought to be so opaque as not to show the ware under it. There are many receipts for making these enamels; but all of them are composed of sand or flints, vitrifying salts, calx of lead, and calx of tin; and the sand must be perfectly vitrified, so as to form a glass considerably fusible. Somewhat less than an equal part of alkaline salt, or twice its weight of calx of lead, is requisite to effect such vitrifications of sand. The calx of tin is not intended to be vitrified, but to give a white opaque colour to the mass; and one part of it is to be added to three or four parts of all the other ingredients taken together. From these general principles, various enamels may be made to suit the different kinds of earths. To make the enamel, lead and tin are calcined together with a strong fire; and the sand is also to be made into a frit with the salts or ashes. The whole is then to be well mixed and ground together. This matter is then to be placed under the furnace, where it is melted and vitrified during the baking of the ware. It is next to be ground in a mill, and applied as above directed.

The preparation of the white enamel is a very essential article in making delft-ware, and one in which many artists fail. M. Boec d'Antic, in a Memoir concerning this kind of ware, published in the Mem. des Savants Etrangers, tom. 6, recommends the following proportions. An hundred pounds of calx of lead are to be mixed with about a seventh part of that quantity of calx of tin for common delft-ware, or a fourth part of calx of tin for the finest kind; an hundred, or an hundred and ten, pounds of fine sand; and about twenty or thirty pounds of sea-salt.—Concerning the earth of which the ware is made, he observes, that pure clay is not a proper material when used alone. Different kinds of earths mixed together are found to succeed better. Pieces of ware made of clay alone, are found to require too much time to dry; and they crack, and lose their form, unless they are made exceedingly thick. An addition of marl diminishes the contraction of the clay; renders it less compact; and allows the water to escape, without altering the form of the ware in drying. It affords also a better ground for the enamel; which appears more glossy and white than when laid on clay alone.—The kinds of clay which are chiefly used in the composition of delft-ware, are the blue and green. A mixture of blue clay and marl would not be sufficiently solid, and would be apt to scale, unless it were exposed to a fire more intense than what is commonly used for the burning of delft-ware. To give a greater solidity, some red clay is added; which, on account of its ferruginous matter, possesses the requisite binding quality. The proportions of these ingredients vary in different works, according to the different qualities of the earths employed. Three parts of blue clay, two parts of red clay, and five parts of marl, form the composition used in several manufactories. M. d'Antic thinks, that the best delft-ware might be made of equal parts of pure clay and pure calcareous earth; but this composition would require that the fire should be continued twice as long as it generally is.