A distinction is to be made herein; for Actual Cauteries are safest in the Operation, because they may be apply'd wheresoever one shall think fit, as also for as long a time, or for any purpose: Whereas the Potential cannot be {201} guided after the same manner. But in Hæmorrhages the Potential Cauteries are most eligible, by reason that the Escar produc'd by 'em not being so speedily form'd, the Vessels are better clos'd, and they are not so subject to open again when it falls off; as it often happens in the Fall of an Escar made by Fire. _In what places are Cauteries usually apply'd?_ In all places where an Attraction is to be made, or an Intemperature to be corrected, or a Flux of Humours to be stopt, by inducing an Escar on the Part: However they are commonly laid upon the Nape of the Neck, between the first and second _Vertebra_; on the outward Part of the Arm in a small Hole between the Muscle _Deltoides_ and the _Biceps_; above the Thigh, between the Muscle _Sartor_, and the _Vastus Internus_; and on the inside of the Knee, below the Flexors of the Leg; observing every where that the Cautery be plac'd near the great Vessels, to the end that it may draw out and cleanse more abundantly. _What is the Composition of the Potential Cauteries?_ They may be made with quick Lime, Soap, and Chimney-Soot; or else take an Ounce of _Sal Ammoniack_, two Ounces of burnt _Roman_ Vitriol, three Ounces of quick Lime, and as many of calcin'd Tartar; mingle the whole Mass together in a _Lixivium_ of Bean-Cod Ashes, and cause it to evaporate gently to a Consistence: Let this Paste be kept for use in a dry place, and in a well-stopt Vessel. Or else the Silver-Cautery, or _Lapis Infernalis_ may be prepar'd after the following manner: {202} Take what quantity you please of Silver, let it be dissolv'd with thrice as much Spirit of Nitre in a Vial, and set the Vial upon the Sand-Fire, to the end that two third parts of its Moisture may evaporate: Then pour the rest scalding-hot into a good Crucible, plac'd over a gentle Fire, and the Ebullition being made, the heat of the Fire must be augmented, till the Matter sink to the bottom, which will become as it were an Oil: Afterward pour it into a somewhat thick and hot Mould, and it will coagulate, so as to be fit for Use, if it be kept in a well-stopt Vial. This Cautery is the best; and an Ounce of Silver will yield one Ounce and five Drams of _Lapis Infernalis_. _What is a Seton?_ It is a String of Silk, Thread, or Cotton, threaded thro' a kind of Pack-Needle, with which the Skin of a Part is to be pierc'd thro', to make an Ulcer therein, that hath almost the same effect as a Cautery. _What is most remarkable in the Application of a Seton?_ It ought to be observ'd, that the String must be dipt in Oil of Roses, and that one end of it must always be kept longer than the other, to facilitate the running of the Humours. _In what Parts is the Seton to be apply'd?_