the act of refining gold or silver by means of a cupel. For this purpose another vessel, called a muffle, is made use of, within which one or more cupels are placed. The muffle is placed upon a grate in a proper furnace, with its mouth facing the door, and as close to it as may be. The furnace being filled up with fuel, some lighted charcoal is thrown on the top, and what fuel is afterwards necessary is supplied through a door above. The cupels are set in the muffle; and being gradually heated by the successive kindling of the fuel, they are kept red-hot for some time, that the moisture which they strongly retain may be completely dissipated: for if any vapours should issue from them after the metal is put in, they would occasion it to sputter, and a part of it to be thrown off in little drops. In the sides of the muffle are some perpendicular flints, with a knob over the top of each, to prevent any small pieces of coals or ashes from falling in. The door, or some apertures made in it, being kept open, for the inspection of the cupels, fresh air enters into the muffle, and passes off through these flints: by laying some burning charcoal on an iron plate before the door, the air is heated before its admission; and by removing the charcoal, or supplying more, the heat in the cavity of the muffle may be somewhat diminished or increased more speedily than can be effected by suppressing or exciting the fire in the furnace on the outside of the muffle. The renewal of the air is also necessary for promoting the scoriification of the lead.

The cupel being of a full red heat, the lead cast into a smooth bullet, that it may not scratch or injure the surface, is laid lightly in the cavity; it immediately melts; and then the gold or silver to be cupelled is cautiously introduced either by means of a small iron ladle, or by wrapping them in paper, and dropping them on the lead with a pair of tongs. The quantity of lead should be at least three or four times that of the fine metal: but when gold is very impure, it requires 10 or 12 times its quantity of lead for cupellation. It is reckoned that copper requires for its scoriification about 10 times its weight of lead: that when copper and gold are mixed in equal quantities, the copper is so much defended by the gold, as not to be separable with less than 20 times its weight of lead; and that when copper is in very small proportion, as a 20th or 30th part of the gold or silver, upwards of 60 parts of lead are necessary for one of the copper. The cupel must always weigh at least half as much as the lead and copper; for otherwise it will not be sufficient for receiving half the scoria: there is little danger, however, of cupels being made too small for the quantity of a gold assay.

The mixture being brought into thin fusion, the heat is to be regulated according to the appearances; and in this consists the principal nicety in the operation. If a various coloured skin rises to the top, which liquefying, runs off to the sides, and is there absorbed by the cupel, visibly staining the parts it enters; if a fresh scoria continually succeeds, and is absorbed nearly as fast as it is formed, only a fine circle of it remaining round the edge of the metal; if the lead appears in gentle motion, and throws up a fume a little way from the surface; the fire is of the proper degree, and the process goes on successfully.

Such a fiery brightness of the cupel as prevents its colour from being distinguished, and the fumes of the lead rising up almost to the arch of the muffle, are marks of too strong a heat; though it must be observed, that the elevation of the fumes is not always in proportion to the degree of heat; for if the heat greatly exceeds the due limits, both the fumes and ebullition will entirely cease. In these circumstances the fire must necessarily be diminished: for while the lead boils and smokes vehemently, its fumes are apt to carry off some part of the gold; the cupel is liable to crack from the hasty absorption of the scoria, and part of the gold and silver is divided into globules, which lying discontinued on the cupel after the process is finished, cannot easily be collected; if there is no ebullition or fumes, the scoriification does not appear to go on. Too weak a heat is known by the dull redness of the cupel; by the fume not rising from the surface of the lead; and the scoria like bright drops in languid motion, or accumulated, or growing confluent all over the metal. The form of the surface affords also a useful mark of the degree of heat; the stronger the fire, the more convex is the surface; and the weaker, the more flat: in this point, however, regard must be had to the quantity of metal; a large quantity being always flatter than a small one in an equal fire. Towards the end of the process, the fire must be increased; for the greatest part of the fusible metal lead being now worked off, the gold and silver will not continue melted in the heat that was sufficient before.

As the last remains of the lead are separating, the rainbow colours on the surface become more vivid, and variously interfect one another with quick motions. Soon after, disappearing all at once, a sudden luminous brightness of the button of gold and silver shows the process to be finished. The cupel is then drawn forwards towards the mouth of the muzzle; and the button, as soon as grown fully solid, taken out.

**CUPPELLING FURNACE.** See Cupelling Furnace.

**CUPID,** in Pagan mythology, the god of love. There seems to have been two Cupids; one the son of Jupiter and Venus, whose delight it was to raise sentiments of love and virtue; and the other the son of Mars and the same goddess, who inspired base and impure desires. The first of these, called Eros, or true love, bore golden arrows, which caused real joy, and a virtuous affection; the other, called Anteros, had leaden arrows, that raised a passion founded only on desire, which ended in satiety and disgust. Cupid was always drawn with wings, to represent his inconstancy; and naked, to show that he has nothing of his own. He was painted blind, to denote that love sees no fault in the object beloved; and with a bow and quiver of arrows, to show his power over the mind. Sometimes he is placed between Hercules and Mercury, to show the prevalence of eloquence and valour in love; and at others is placed near Fortune, to signify that the success of lovers depends on that inconstant goddess. Sometimes he is represented with a helmet on his head and a spear on his shoulder, to signify that love disarmeth the fiercest men; he rides upon the backs of panthers and lions, and uses their manes for a bridle, to denote that love tames the most savage beasts. He is likewise pictured riding upon a dolphin, to signify that his empire extends over the sea no less than land.

**CUPOLA,** in Architecture, a spherical vault, or the round top of the dome of a church, in the form of a cup inverted.

**CUPPING,** in Surgery, the operation of applying cupping-glasses for the discharge of blood and other humours by the skin. See Surgery.

**CUPRESSUS,** the cypress tree: A genus of plants belonging to the conoecea class; and in the natural method ranking under the 51st order, Coniferae. See Botany Index.

The wood of the *sempervirens,* or evergreen cypress, is said to resist worms, moths, and putrefaction, and to last many centuries. The coffins in which the Athenians were wont to bury their heroes, were made, says Thucydides, of this wood; as were likewise the chests containing the Egyptian mummies. The doors of St Peter's church at Rome were originally of the same materials. These, after lasting upwards of 600 years, at the end of which they did not discover the smallest tendency to corruption, were removed by order of Pope Eugenius IV. and gates of brass substituted in their place. The same tree is by many eminent authors recommended as improving and invigorating the air by its balsamic and aromatic exhalations; upon which account many ancient physicians of the eastern countries used to send their patients who were troubled with weak lungs to the island of Candia, where these trees grew in great abundance; and where, from the salubrious air alone, very few failed of a perfect cure. In the same island, says Miller, the cypresses were so lucrative a commodity, that the plantations were called *dos filiae*; the felling of them being reckoned a daughter's portion. Cypress, says Mr Porrocke, is the only tree that grows towards the top of Mount Lebanon, and being nipped by the cold, grows like a small oak. Noah's ark is commonly supposed to have been made of this kind of wood.

**CUPRUM AMMONIACALE.** See Chemistry Index. This preparation is recommended in some kinds of spasmodic diseases, given in the dose of one or two grains.