Beccher’s great merit was the contrivance of a chemical theory, by which all the known facts were connected together and deduced from one general principle. But as this theory was adopted and considerably modified by Stahl, it will be better to lay a sketch of it before the reader, after mentioning a few particulars of the life and labours of one of the most extraordinary men whom Germany has produced; a man who, in spite of the moroseness and haughtiness of his character, and in spite of the barbarity of his style, raised himself to the very first rank as a man of science; and had the rare or almost unique fortune of giving laws at the same time to two different and important sciences, which he cultivated together, without letting his opinions respecting the one influence him with regard to the other. These sciences were chemistry and medicine.
George Ernest Stahl was born at Anspach, in the year 1660. He studied medicine at Jena under George Wolfgang Wedel; and got his doctor’s degree at the age of twenty-three. Immediately after this he began his career as a public lecturer. In 1687 the Duke of Weimar gave him the title of physician to the court. In 1694 he was named, at the solicitation of Frederick Hoffmann, second professor of medicine in the University of Halle, which had just been established. Hoffmann and he were at that time great friends, though they afterwards quarrelled. Both of them were men of the very highest talents and both were the founders of medical systems which, of course, each was anxious to support. Hoffmann had greatly the superiority in elegance and clearness of style, and in all the amenities of polite manners. But perhaps the moroseness of Stahl, and the obscurity, or rather mysticism of his style, contributed equally with the more amiable qualities of Hoffmann to excite the attention and produce the veneration with which he was viewed by his pupils, and, indeed, by the world at large.
At Halle he continued as a teacher of medicine for twenty-two years. In 1716 he was appointed physician to the King of Prussia. In consequence of this appointment he left Halle, and resided in Berlin, where he died in the year 1734, in the seventy-fifth year of his age. Notwithstanding the great figure that Stahl made as a chemist, there is no evidence that he ever taught that science in any public school. The Berlin Academy had been founded under the superintendence of Leibnitz, who was its first president; and therefore existed when Stahl was in Berlin: but, till it was renovated in 1745 by Frederick the Great, this academy possessed but little activity, and could scarcely, therefore, have stimulated Stahl to attend to chemical science. However, his Chymia rationalis et experimentalis was published in 1720, while he resided in Berlin. The same date is appended to the preface of his Fundamenta Chymiæ; but, from some expressions in that preface, it must, I should think, have been written, not by Stahl, but by some other person.[180] I suspect that the book had been written by some of his pupils, from the lectures of the author while at Halle. If this was really the case, it is obvious that Stahl must have taught chemistry as well as medicine in the University of Halle.
Stahl’s medical theory is not less deserving of notice than his chemical. But it is not the object of this work to enter into medical speculations. Like Van Helmont, he resolved all diseases into the actions of the soul, which was not merely the former of the body, but its ruler and regulator. When any of the functions are deranged, the soul exerts itself to restore them again to their healthy state; and she accomplishes this by what in common language is called disease. The business of a medical man, then, is not to prevent diseases, or to stop them short when they appear; because they are the efforts of the soul, the vis medicatrix naturæ, to restore the deranged state of the functions: but he must watch these diseases, and prevent the symptoms from becoming too violent. He must assist nature to produce the intended effect, and check her exertions when they become abnormal. It was a kind of modification of this theory, or rather a mixture of the Stahlian and Hoffmannian theories, that Dr. Cullen afterwards taught in Edinburgh with so much eclat. And these opinions, so far as medical theories have any influence on practice, still continue in some measure prevalent. Indeed, much of the vulgar practice followed by medical men, chiefly in consequence of the education which they have received, is deduced from these two theories. But it would be too great a digression from the object of this work to enter into any details: suffice it 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.