a concrete gummy resinous juice, brought from the East Indies, usually in large masses, composed of little lumps or tears, of a milky colour, but soon changing, upon being exposed to the air, to a yellowish hue. We have no certain account of the plant which affords this juice: the seeds usually found among the tears resemble those of the umbelliferous class. It has been, however, alleged, and not without some degree of probability, that it is an exudation from a species of the Ferula, another species of which produces the afaetida. The plant producing it is said to grow in Nubia, Abyssinia, and the interior parts of Egypt. It is brought to the western parts of Europe from Egypt, and to England from the Red Sea, by some of the ships belonging to the East India Company trading to those parts. Such tears as are large, dry, free from little stones, seeds, or other impurities, should be picked out, and preferred for internal use: the coarser kind is purified by solution and colature, and then carefully insufflating it; unless this be artfully managed, the gum will lose a considerable deal of its more volatile parts. There is often vended in the shops, under the name of strained gum ammoniacum, a composition of ingredients much inferior in virtue.

Ammoniac has a nauseous sweet taste, followed by a bitter one: and a peculiar smell, somewhat like that of galbanum, but more grateful; it softens in the mouth, and grows of a whiter colour upon being chewed. Thrown upon live coals, it burns away in flame: it is in some measure soluble in water and in vinegar, with which it assumes the appearance of milk; but the resinous part, amounting to about one half, subsides on standing.

Ammonium is a useful deobstruent, and frequently prescribed for opening obstructions of the abdominal viscera, and in hysterical disorders occasioned by a deficiency of the menstrual evacuations. It is likewise supposed to deterge the pulmonary vessels; and proves of considerable service in some kinds of asthmas, where the lungs are opprefled by viscid phlegm; in this intention, a solution of gum ammoniac in vinegar of squills proves a medicine of great efficacy, though not a little unpleasent. In long and obstinate colics proceeding from viscid matter lodged in the intestines, this gummy resin has produced happy effects, after the purges and the common emmenatives had been used in vain. Ammoniac is most commodiously taken in the form of pills; about a scruple may be given every night, or oftener. Externally, it softens and ripens hard tumours: a solution of it in vinegar stands recommended by some for resolving even fibrous swellings. A plaster made of it and squill-vinegar is recommended by some in white swellings. A dilute mixture of the same is likewise rubbed on the parts, which are also fumigated with the smoke of juniper berries. In the shops is prepared a solution of it in pennyroyal water, called from its milky colour lac ammoniaci. It is an ingredient also in the squill pills.

Sal Ammoniac, the old name of muriate of ammonia, a native salt, composed of ammonia, or volatile alkali, and muriatic acid, which was generated in those large inns or caravanserais where the crowd of pilgrims coming from the temple of Jupiter Ammon used to lodge; who, in those parts, travelling upon camels, and those creatures when in Cyrene, a province of Egypt, where that celebrated temple stood, urining in the stables, or (say some) in the parched sands, out of this urine, which is remarkably strong, arose a kind of salt, denominated sometimes (from the temple) Ammoniac, and sometimes (from the country) Cyrenaic. Since the cessation of these pilgrimages, no more of this salt is produced there; and, from this deficiency,