CRYSTAL

is the geometrical form po e ed by a vast number of mineral and saline substances; as also by many vegetable and animal products. The integrant particles of matter have undoubtedly determinate forms, and combine with one another, by the attraction of cohesion, according to certain laws, and points of polarity, whereby they a ume a vast variety of secondary crystalline forms. The investigation of these laws belongs to crystallography, and is foreign to the practical purpose of this volume. Instructions are given under each object of manufacture which requires crystallization, how to conduct this proce ; see Borax , Salt , . CUDBEAR was first made an article of trade in this country, by Dr. Cuthbert Gordon, from whom it derived its name, and was originally manufactured on a great scale by Mr. G. Mackintosh at Glasgow, nearly 60 years ago. Cudbear or persio is a powder of a violet red colour, difficult to moisten with water, and of a peculiar but not disagreeable odour. It is partially soluble in boiling water, becomes red with acids, and violet blue with alkalis. It is prepared in the same way as archil , only toward the end the substance is dried in the air, and is then ground to a fine powder, taking care to avoid decomposition, which renders it glutinous. In Scotland they use the lichen tartare us, more rarely the lichen cal care us, and omphalodes; most of which lichens are imported from Sweden and Norway, under the name of rock mo . The lichen is suffered to ferment for a month, and is then stirred about to allow any stones which may be present to fall to the bottom. The red ma is next poured into a flat ve el, and left to evaporate till its urinous smell has disappeared, and till it has a umed an agreeable colour verging upon violet. It is then ground to fine powder. During the fermentation of the lichen, it is watered with stale urine, or with an equivalent ammoniacal liquor of any kind, as in making archil. CUPELLATION; is a mode of analyzing gold, silver, palladium, and platinum, by adding to small portions of alloys, containing these metals, a bit of lead, fusing the mixture in a little cup of bone earth called a cupel , then by the joint action of heat and air, oxidizing the copper, tin, ., present in the precious metals. The oxides thus produced, are di olved and carried down into the porous cupel in a liquid state, by the vitrified oxide of lead. See A ay , Gold , and Silver .