to say, that the rival theories of Hoffmann and Stahl for many years divided the medical world in Germany, if not in the greater part of Europe. It was no small matter of exultation to so young a medical school as Halle, to have at once within its walls two such eminent teachers as Hoffmann and Stahl. Let us turn our attention to the chemical writings of Stahl. Of these the most important is his Fundamenta Chymiæ dogmaticæ et experimentalis. It is divided, like the chemistry of Boerhaave, into a theoretical and practical part. The perusal of it is very disagreeable, as it is full of German words and phrases, and symbols are almost constantly substituted for words, as was at that time the custom. His definition of chemistry is much more exact than Boerhaave’s. It is, according to him, the art of resolving compound bodies into their constituents, and of again forming them by uniting these constituents together. He is inclined to believe with Beccher, that the simple principles are four in number. The _mixts_ are compounds of these principles; and he shows by the doctrine of permutations that if we suppose the simple principles four, then the number of mixts will be 40,340. He treats in the first place of _mixts_, _compounds_, and _aggregates_. The first object of chemistry is _corruption_, the second _generation_. Of these he treats at considerable length, giving an account of the different chemical processes, and of the apparatus employed. He next treats of _salts_, which he defines mixts composed of water and earth, both simple and pure, and intimately united. The salts are vitriol, alum, nitre, common salt, and sal ammoniac. He next treats of more compound salts. These are sugar, tartar, salts from the animal and salts from the mineral kingdom, and quicklime. After this comes sulphur, cinnabar, antimony, the sulphur of vitriol, the sulphur of nitre, resins, and distilled oils. Then he treats of water, which he divides into aqua _humida_ or common water, and aqua _sicca_ or mercury. Next he treats of earths, which are of two kinds, viz., _friable earths_, such as _clay_, _loam_, sand, &c., and metallic earths constituting the bases of the metals. He next treats of the metals; and, as a preliminary, we have a description of the method of smelting, and operating upon the different metals. The metals are then described successively in the following order: Gold, silver, copper, iron, tin, lead, bismuth, zinc, antimony. To this part of the system are added three sections. The first treats of mercuries, the second of the philosopher’s stone, and the third of the universal medicine. We must not suppose that Stahl was a believer in these ideal compositions; his object is merely to give a history of the different processes which had been recommended by the alchymists.