Mercury, like most other metallic substances, is found in the earth, either in a pure state, or in that of an ore. The first has been called _virgin-mercury_, and is in general found by the miners in drops or small grains; sometimes indeed it is observed in larger quantities, and forms the appearance of small streams. In the state of ore, it is most frequently combined either with sulphur, or with earthy matters; from which it is readily extracted by distillation. It is found in both these states in different places of Europe, particularly in Spain and in Hungary; but Britain is principally supplied with it from the East-Indies. Mercury was not unknown to the antients. In the early ages of medicine, indeed, it seems to have been esteemed a virulent poison; but it has now, for some centuries past, been much, and successfully, employed for the purposes of medicine, as well as of other arts. The Arabians were the first who employed it in the cure of diseases; but they seem to have used it externally only, and applied it for discussing tumors, cleansing ulcers, and curing cutaneous eruptions. Soon after the introduction of the venereal disease into Europe, mercury was found to be the most expeditious and most effectual, if not the only certain, remedy. The advantages which are to be derived from its employment in this disease, both when applied externally, and taken internally, have now been confirmed for a length of time too considerable for allowing the least foundation either to doubt its efficacy, when properly used, or to dread its deleterious effects, when judiciously managed. The effects of mercury on the human system in a sound state are very various. When mercury, in its crude state, is introduced by the mouth into the alimentary canal, it passes off by stool, without producing any effect. It has indeed been alledged, that in this state, in some morbid affections, it may be useful in removing obstructions by its weight. But it is to be remembered, that, in a great part of its passage through the intestines, it rises in opposition to gravity, and that it is very apt to divide in such a manner as to make its way through very small openings. This effect, then, is perhaps in general, if not always, to be disregarded. When mercury is prepared in such a manner as to be readily soluble in the fluids of the human body, the effects it produces are much diversified. Its action is often immediately exerted upon the stomach; in which case vomiting is produced. This effect is observed from the use of many mercurial preparations. The brown and green precipitates and calcined mercury act as rough and strong emetics; but the preparation principally used, where it is intended to act as an emetic, is the yellow precipitate, or Turpeth mineral.