in pharmacy, a dry medicine well broken, either in a mortar by grinding or by some chemical operation.

Gun Powder. See Gunpowder. See also Observations on Gunpowder in the Irish Transactions, p. 97, cl. 3, Science, by Mr Napier.

Powder-Chest, certain small boxes charged with powder and a quantity of old nails or splinters of iron, and fastened occasionally on the deck and sides of a ship, in order to be discharged on an enemy who attempts to seize her by boarding. These cases are usually Powder ally from 12 to 18 inches in length, and about eight or ten in breadth, having their outer or upper part terminating in an edge. They are nailed to several places of the quarter-deck and bulk-head of the waist, having a train of powder, which communicates with the inner apartments of the ship, so as to be fired at pleasure to annoy the enemy. They are particularly used in merchant-ships which are furnished with close-quarters to oppose the boarders.

Powder Magazine, a bomb-proof arched building, to contain powder in fortified places.

Powder for the Hair. The best sort is starch well pounded and sifted, and generally prepared with some perfume.

James's Powder. See James's Powder. In the Philosophical Transactions for 1791, p. 317, there is a paper by Dr Pearlson, containing experiments and observations on James's powder. Dr Pearlson says, it was originally a patent medicine; but it is well known that it cannot be prepared by following the directions of the specification in the court of chancery. His observations and experiments, therefore, he thinks, may explain the nature and manner of preparing this medicine, and perhaps may extend the history of antimony. The result of the whole, in Dr Pearlson's own words, is as follows:

1. James's powder consists of phosphoric acid, lime, and antimonial calx; with a minute quantity of calx of iron, which is considered to be an accidental substance. 2. Either these three essential ingredients are united with each other, forming a triple compound, or phosphorated lime is combined with the antimonial calx, composing a double compound in the proportion of about 57 parts of calx and 43 parts of phosphorated lime. 3. This antimonial calx is different from any other known calx of antimony in several of its chemical qualities. About three-fourths of it are soluble in marine acid, and afford Algaroth powder; and the remainder is not soluble in this menstruum, and is apparently vitrified. It also appears, that by calcining together bone-ashes, that is, phosphorated lime and antimony in a certain proportion, and afterwards exposing the mixture to a white heat, a compound was formed, consisting of antimonial calx and phosphorated lime in the same proportion, and possessing the same kind of chemical properties as James's powder.