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, of 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 clasps. 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 insipidifying 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.

Ammoniac 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 asthma, where the lungs are oppressed 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 unpleasant. 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 carminatives 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 scirrhouss swellings.

Sal Ammoniac, a volatile salt, of which there are two kinds, ancient and modern. The ancient sort, described by Pliny and Dioscorides, was a native salt, 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, traveling upon camels, and those creatures when in Cyrene, a province of Egypt, where that celebrated temple stood, urinating 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, Cyreniac. Since the cessation of these pilgrimages, no more of this salt is produced there; and, from this deficiency, some suspect there never was any such thing: But this suspicion is removed, by the large quantities of a salt, nearly of the same nature, thrown out by mount Ætna. The characters of the ancient sal am- AMMONITÆ, in natural history. See CORNU AMMONIS.