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tillation ; and vegetable oils are procured by expression, infusion, and distillation. The oils chiefly consumed in lamps are procured from certain animal matters by boiling and expression. Such are the train and spermaceti oils obtained from whales, porpoises, and other fish (See Spermaceti). Castor Oil, so much used in medicine, is obtained from a West Indian tree called Palma Christi.

PUMICE STONE, OR PUMEX.

A hard substance, frequently ejected from volcanoes, of a white, grey, black, or brown colour. It is very porous, and so light as to float on water. It is of great utility in smoothing wood, paste board, metal, and stone, as from its harsh and brittle texture it removes all inequalities from the surface. From its resemblance to the frothy slag produced in our iron furnaces, its formation has been attributed to that kind of froth which naturally rises to the top of the melted matter in the volcanic crater. It is found in abundance in some Islands of the Archipelago, and is much used at Naples and Sicily for building.

POUNCE.

The fine powder of Gum Sandarach, frequently rubbed upon paper in parts from which writing has

been erased, in order to prevent the ink from running, and enable the writer to rectify errors. Charcoal dust is also called Pounce, and is much used by embroiderers, who mark their patterns by passing it over holes pricked in work. Pounce is also obtained from a species of juniper tree, and from the cuttle-bone (51).

PEARLASH.

A kind of fixed alkaline salt, prepared by melting the salts extracted from the ashes of burnt wood, and again reducing them to dryness, evaporating the moisture and calcining them for a considerable time in a moderately heated furnace. Pearlash is principally used in the manufacture of glass, and it requires no further preparation, except when very great transparency is required ; also in bleaching. These ashes are chiefly prepared in Germany, Russia, Poland, and America. Their goodness consists in a uniform and wbite appearance, but they are subject to adulteration by a mixture of common salt.

PEPPER, OR PIPER May be divided into three sorts, the black, the white, and the long. The black grows upon the Piper plant in clusters, and the fruit round the bud, which is white, produces berries containing the Pepper corns. The fruit is first green, then red, and afterwards dark brown; it is commonly gathered in October, and exposed several days to the sun. The leaves have a pungent taste, and are strongly scented. The wood of the plant resembles our vine, and when it rises into a stem requires a prop. It is not difficult to cultivate, but must be planted in a rich soil. It is propagated by shoots, and does not produce fruit until three years. During the succeeding three years it will yield six or seven pounds, after which time it gradually declines. This plant requires a great deal of sun, and it is necessary frequently to prune its top. It is a hot, aromatic, dry spice, brought from the East Indies, chiefly from the Isles of Java, Sumatra, and the coast of Malabar. The white Pepper is prepared from the black by rubbing off the outward bark after it has been loosened by steeping in sea water, and been exposed to the sun to dry: this process deprives it of a great deal of heat; there is also a white Pepper produced on a species of the same plant, and considered nearly equal to the black. The Long Pepper is also produced on a plant of the same genus, and is used chiefly in medicine. Pepper is used for seasoning, or as a peptic, and the East Indians frequently take it infused in water to create an appetite ; sometimes they preserve it in vinegar. It is about an inch in length, brownish and rather thick, extremely pungent, and salt to the taste.

PEWTER.

A compound metal, manufactured into spoons, plates, and a variety of domestic and other articles. It is a mixture of copper, brass, and tin, but there are other compositions frequently used in the formation of pewter, viz. bismuth and antimony, in different proportions. From the properties of the ingredients formivg this metal, cleanliness in the use of domestic articles made of it is highly necessary, and acids or fermented liquors should never be allowed to remain in them.

POTASS.

An alkaline salt, chiefly procured by lixiviation from the ashes of burnt wood and certain vegetables, particularly of the plant kali. That obtained from bean stalks, the loppings of trees, vines, &c. is inferior in quality. The Russian Potass is made from the wood of the oak, beech, &c. and it appears that good Potass may be made in all places where vegetable substances abound. The best is brought from Spain. It is employed in bleaching, making alum, cleaning wool, dyeing, &c. also in chymistry and medicine,

PEARLS.

Hard, white, glossy concretions, found generally in the shell of a fish called the East Indian Pearl Oyster, and in muscles, but the latter are inferior in value. They are usually round, but sometimes of a pear shape. Spring and autumn are the seasons in which the divers are employed in fishing for them. These divers descend to those parts where the fish lie, which, adhering firmly to the sides of the rocks, require to be pulled off, either with the hands of those searching for them, or with an iron rake. Having filled a net the signal is given and they are drawn up. Experienced divers will remain under water for a considerable time, during which they hold their breath, without the use of oils or any liquors, but babit alone can render them capable of doing so. The greatest danger to which divers are exposed is the becoming a prey to the inhabitants of the deep. The oysters thus obtained are put into pits prepared for them, and covered with sand; this, with the rain and sun, soon causes them to open and die, when the flesh dries up and the Pearls fall into the pit. These are sifted, after being cleaned and dried. The small or seed Pearls are sold by the ounce, and the larger ones by auction. The best are found in Asia and Africa.

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