After this inquiry concerning the operation of mercury in the venereal disease, I next proceed to make some observations with regard to its use. Mercury has been employed in the cure of the venereal disease in a great variety of forms. Most of these, upon their first introduction into practice, have been extolled as the safest and most effectual method of using it in every case. Experience, however, sufficiently demonstrates, that this holds with regard to no mercurial preparation hitherto discovered. Whether such a preparation may yet be discovered, is difficult to say. In this treatise, I have not proposed any mercurial which was not formerly in use. But if, on the one hand, I have no title to lay claim to the merit of a discovery, I cannot, on the other, be charged with being the first proposer of any dangerous practice. In treating of the use of mercurials in _lues venerea_, my aim has been different from that of most authors. What I have principally had in view, is not so much to recommend any particular preparation, as to determine the comparative advantages of some of the most effectual ones at present in common use. I have likewise endeavoured to point out those circumstances to which each is best adapted. To this I have subjoined the principal cautions to be observed in the employment of mercurials; those more especially which respect the nature of the medicine, the condition of the patient, and the necessary regimen. On these subjects, a good collection of observations would unquestionably be of the highest utility. How far I have succeeded, must be left to others to determine. To those who imagine I have not altogether failed, I need offer no excuse for having published. To those who are of a contrary opinion, it will be sufficient to observe, that every attempt to be serviceable should apologise for itself. ------------------------------------------------------------------------ CHAP. I. _Of the General Properties of Mercury._ MERCURY is a production of the mineral kingdom. In its natural state, it is of an opaque metallic substance, of very considerable specific gravity. To the eye, it appears like melted lead, or silver; from which it has derived the name of _quicksilver_. In this condition, when freed from every admixture, it has neither any perceptible smell nor taste; and, as its application to the most sensible parts of the body occasions no irritation, we may conclude, that it is void of all acrimony. By very intense cold, artificially excited, mercury may be brought to a solid form; but, in the greatest natural cold hitherto known, it remains always in a fluid state. By heat it is rendered very volatile, exhaling totally in fumes; these fumes, upon being exposed to cold, condense again into running mercury.