a celebrated mercurial medicine, the method of preparing which was purchased by the French government, and has since been published by M. Richard.

The first, and what, according to Mr Keyser, is the most essential operation, consists in separating the mercury very exactly from all heterogeneous matter, by reducing it to an æthiops. This is effected by means of an hydraulic machine, a plan of which Mr Keyser intended to have given to government before his death; but although he did not live to accomplish his reformation, his family still offer to do it when desired. According to the description given by M. Richard, this machine consists of a number of buckets, in which mercury is triturated with water, till the water acquires a black colour. This water, upon standing, deposits a sediment, which, being dried by a proper heat, is the æthiops required.

The second process consists in revivifying the mercury by distillation, in freeing it from all oily matters, by means of quick-lime, in detaching this quick-lime, by repeated washings, and afterwards in drying it by means of a sand heat.

The third operation consists in the reduction of the mercury purified by this process to a red calx, by means of heat. In conducting this operation, Mr Keyser advises, that the mercury be put into glass matrasses, a small quantity only in each. For the proper degree of heat, he directs those who would practise the operation to consult Lemery and other chemists.

The fourth operation is, the dissolution of the calcined mercury, obtained by the former process, in distilled vinegar, by means of trituration. A pound of this mercury may be dissolved in eight pints of vinegar, by rubbing it for an hour or two in a mortar, which should be kept solely for that purpose. Care must also be taken that the vinegar be not distilled in a metallic but in a glass vessel.

The fifth process consists in the intimate mixture of this vinegar, impregnated with mercury, with manna. Each pound of the vinegar containing about two ounces of mercury, will require two pounds of manna. They must be rubbed together upon marble stones till they acquire a uniform consistence, which will be liquid to such a degree as to pass through a hair-cloth, for separating the impurities of the manna. After being managed in this manner, it must be spread upon a marble slab, and left to dry there, without the assistance of fire, till it acquires such a consistence as not to run. run off upon the table being turned to its side. It must then be placed before the fire, and at the same time moved from one part of the stone to another, by means of a knife, furnished with a large pliant blade. By this means, it is perfectly prepared for forming the pills.

The sixth and last process consists in the formation of the mass thus prepared into pills. These Mr Keyser made to weigh either three grains or a grain and a half; the first for robust, the last for delicate constitutions.

To this account given for the preparation of these pills, Mr Keyser has added some reflections, by way of supplement. He observes, that, by the purification of the mercury from distillation, a great quantity of heterogeneous matter is separated from it. This, however, by no means frees it completely from all foreign matter. And, as mercury purified, upon being calcined and dissolved in vegetable acid, is a much more powerful medicine than mercury calcined without purification, he concludes, that repeated purifications would render it still more active.

Another remark which he gives, respects the dissolution of the mercurius calcinatus in the distilled vinegar. He observes, that the mercury thus dissolved may be made to unite with running mercury, and to form a very singular product. He formerly mentioned, that a pound of this mercurius calcinatus was to be dissolved in eight pints of vinegar. If to this be added two pounds of running mercury, and the agitation continued, a substance will arise to the surface in the form of cream. This being removed by the assistance of a wooden spoon, more will continue to rise as long as the agitation is continued. The cream being dried and incorporated with manna, in the proportion of one part of the cream to eight of manna, forms a very useful purgative, and is said to be an effectual remedy against recent venereal complaints, particularly against chancre.

Mr Richard concludes his account of Keyser's pills, with observing, that he considers it to be, without exception, the most effectual remedy for the venereal disease hitherto discovered. But before entering upon the detail, he remarks, that it is his opinion the process may be much abridged, without diminishing the efficacy of the medicine. He judged it proper, however, to deliver to the public the method of preparing the pills in Mr Keyser's own words; and he has not afterwards pointed out the improvements he proposes.