Costus dulcis officinarum C. B. Coitus ara-hicus Linn. Costus: a root, brought from the East Indies, about the size of the finger, of a pale greyish or whitish colour on the outside, and yellow within. An Arabian, a bitter, and a sweet costus were formerly distinguished in the shops: whether they were, as some suspect, the roots of different plants, or, as others, of one and the same plant in different states, does not fully appear. At present, only one sort is met with, and this but rarely.

This root has been recommended as a stomachic, uterine, diaphoretic, and diuretic. The editor of the Wirtemberg pharmacopoeia observes, that it impregnates the urine, like the turpentines, with a violet smell. The smell of the root itself approaches to that of violets or Florence orris: its taste is warm and bit-terish. Both the smell and taste are consined chiefly to the brittle cortical part, the internal tough woody matter having very little of either.

Decoctions of costus in water are of a brown-ish colour, a bitter taste, and less grateful smell than the root in substance: in evaporation they diffuse a very disagreeable scent: the infpiffated extract is moderately bitter, of scarcely any particular flavour, in quantity amounting to no less than two thirds the weight of the root; in keeping, it soon grows mouldy, and dusty on the surface. The spirituous tincture is of a bright yellow colour, a bitter aromatic taste, and a more agreeable smell than the watery decoclion; infpiffated, it yields a very warm pungent, bitter extract, of an aromatic flavour, less grateful than that of the coftus itself, in quantity not exceeding one ninth the weight of the root.

Creta Ph. Lond. & Edinb. Chalk: a pure white mineral calcareous earth, met with in most parts of the world, of various degrees of hardnefs. The softer masses, included in sea shells (which are commonly in chalk pits) called from their figure chalk eggs, are by many preferred to the others for medicinal use.

There are innumerable concretes in the mineral kingdom, of the same general nature with chalk; or which consist chiefly, or wholly, of the same earth, formed into masses, which differ from one another little otherwis than in their external appearance, compactnes, or texture-Such are the limestones; the marbles; some of the marles; the fine earth called agaricus mine-ralis, medulla taxi or lac lunae: the transparent crystalline concretes called spars; most of the petrefactions; and most of the ftalactitae, or the earthy matter, which, in its concretions from waters, incrustates the sides of caverns, or hangs in icicles from the tops. Many of these bodies were formerly introduced into medicine, from an erroneous supposition of their poffefting dis-tincl: qualities: chalk, one of the purest of them, is the only one now retained in practice; nor would the art suffer any detriment, if a like reduction was made in the analogous bodies furnished by the animal kingdom.

The distinguishing characters of this earth, in all its forms, are, its not dissolving in the vitriolic acid, though readily dissolving in all the others; its being precipitated by the vitriolic acid from its solutions in the others, and being thus changed into a selenites; its being convertible, by calcination with a strong fire, into quicklime; and its melting easily, with certain vitrefactive fluxes, as borax, into a transparent glass. In this last property it differs from the calcareous animal earths; which appear to be unvitrescible, communicating, to a large proportion of vitreous matters, an spake milkiness.

Pure chalk is a very useful absorbent in cardialgic and other complaints from acidities in the first passages. For this purpose it is formed, in the shops, into troches, with sugar and a little nutmeg, and generally with the addition of some of the other absorbent earths, which add nothing to its virtue; and into juleps, by mixing the chalk, levigated into a subtile powder, with water, in the proportion of half an ounce to a pint; with the addition of three drams of sugar, and one ounce of gum-arabic, to give some consistence to the liquor, so as to enable it to keep the powder suspended. *The Edinburgh college have now directed a powder, confiding of four ounces of prepared chalk, with a dram and a half of nutmeg and a dram of cinnamon, to supply the place of the cardialgic troches. The compound astringent powders of the London pharmacopoeia which formerly had their name from bole, are now improved by the substitution of chalk to that sub-stance, and have in consequence changed their name. In these, the chalk constitutes some-what less than half the weight.

When chalk is combined with such acids, as may be deemed moft analogous to those which are preternaturally generated in the human sto-mach, as four milk and four vegetable liquors; the compounds prove somewhat more austere than those resulting from the coalition of the same acids with the animal absorbents: hence chalk, given in cases of acidities, is generally observed to bind the belly more; and thus to prove more injurious in costive habits, and more beneficial in fluxes: two drams given in a dbse, and repeated at proper intervals, have often effected a speedy cure both in simple diarrhoeas and in dysenteries. But that it has any astrin-gent power, as many have suppofed, independently of its combination with acids, or in disorders where there are no acid juices in the first passages to dissolve it, is not so clear: the sense of aftringency, which the chalk in substance produces in the mouth, appears to proceed, like that of the bolar earths, only from its adhering to the part and imbibing its moisture.

Mistura cre-tacea Ph. Lond.

Pulv. Cre-taceus Ph, Ed.

Pulv. e Creta comp. fine & cum Opio Ph. Lond.