Young Black laid down a very comprehensive and serious plan of study. This appears from a number of note-books found among his papers. There are some in which he seems to have inserted every thing as it took his fancy, in medicine, chemistry, jurisprudence, or matters of taste. Into others, the same things are transferred, but distributed according to their scientific connexions. In short, he kept a journal and ledger of his studies, and has posted his books like a merchant. What particularly strikes one in looking over these books, is the steadiness with which he advanced in any path of knowledge. Things are inserted for the first time from some present impression of their singularity or importance, but without any allusion to their connexions. When a thing of the same kind is mentioned again, there is generally a reference back to its fellow; and thus the most isolated facts often acquired a connexion which gave them importance.
He went to Edinburgh to finish his medical studies in 1750 or 1751, where he lived with his cousin german, Mr. James Russel, professor of natural philosophy in that university.
It was the good fortune of chemical science, that at this very time the opinions of professors were divided concerning the manner in which certain lithontriptic medicines, particularly lime-water, acted in alleviating the excruciating pains of the stone and gravel. The students usually partake of such differences of opinion: they are thereby animated to more serious study, and science gains by their emulation. This was a subject quite to the taste of young Mr. Black, one of Dr. Cullen’s most zealous and intelligent chemical pupils. It was, indeed, a most interesting subject, both to the chemist and the physician.
All the medicines which were then in vogue as solvents of urinary calculi had a greater or less resemblance to caustic potash or soda; substances so acrid, when in a concentrated state, that in a short time they reduce the fleshy parts of the animal body to a mere pulp. Thus, though they might possess lithontriptic properties, their exhibition was dangerous, if in unskilful hands. They all seemed to derive their efficacy from quicklime, which again derives its power from the fire. It was therefore very natural for them to ascribe its power to igneous matter imbibed from the fire, retained by the lime, and communicated by it to alkalies, which it renders powerfully acrid. Hence, undoubtedly, the term caustic applied to the alkalies in that state, and hence also the acidum pingue of Mayer, which was a peculiar state of fire. It appears from Dr. Black’s note-books, that he originally entertained the opinion, that caustic alkalies acquired igneous matter from quicklime. In one of them he hints at some way of catching this matter as it escapes from lime, while it becomes mild by exposure to the air; but on the opposite blank page is written, “Nothing escapes—the cup rises considerably by absorbing air.” A few pages further on, he compares the loss of weight sustained by an ounce of chalk when calcined, with its loss while dissolved in muriatic acid. Immediately after this, a medical case is mentioned, which occurred in November, 1752. Hence it would appear, that he had before that time suspected the real cause of the difference between limestone and burnt lime. He had prosecuted his inquiry with vigour; for the experiments with magnesia are soon after mentioned.
These experiments laid open the whole mystery, as appears by another memorandum. “When I precipitate lime by a common alkali there is no effervescence: the air quits the alkali for the lime; but it is lime no longer, but C. C. C.: it now effervesces, which good lime will not.” What a multitude of important consequences naturally flowed from this discovery! He now knew to what the causticity of alkalies is owing, and how to induce it or remove it at pleasure. The common notion was entirely reversed. Lime imparts nothing to the alkalies; it only removes from them a peculiar kind of air (carbonic acid gas) with which they were combined, and which prevented their natural caustic properties from being developed. All the former mysteries disappear, and the greatest simplicity appears in those operations of nature which before appeared so intricate and obscure.
Dr. Black had fixed upon this subject for his inaugural dissertation, and was induced, in consequence, to defer applying for his degree till he had succeeded in establishing his doctrine beyond the possibility of contradiction. The inaugural essay was delivered at a moment peculiarly favourable to the advancement of science. Dr. Cullen had been just removed to Edinburgh, and there was a vacancy in the chemical chair in Glasgow: it could not be bestowed better than on such an alumnus of the university—on one who had distinguished himself both as a chemist and an excellent reasoner; for few finer models of inductive investigation exist than are displayed in Black’s essay on quicklime and magnesia. He was appointed professor of anatomy and lecturer on chemistry in the University of Glasgow in 1756. It was a fortunate circumstance both for himself and for the public, that a situation thus presented itself, just at the time when he was under the necessity of settling in the world—a situation which allowed him to dedicate his talents chiefly to the cultivation of chemistry, his favourite science.
When Dr. Black took his degree in medicine, he sent some copies of his essay to his father at Bordeaux. A copy was given by the old gentleman to his friend, the President Montesquieu, who, after a few days called on Mr. Black, and said to him, “Mr. Black, my very good friend, I rejoice with you; your son will be the honour of your name and family.” This anecdote was told Professor John Robison by the brother of Dr. Black.
Thus Dr. Black, while in Glasgow, taught at one and the same time two different classes. He did not consider himself very well qualified to teach anatomy, but determined to do his utmost; but he soon afterwards made arrangements with the professor of medicine, who, with the concurrence of the university, exchanged his own chair for that of Dr. Black.
Black’s medical lectures constituted his chief task while in Glasgow. They gave the greatest satisfaction by their perspicuity and simplicity, and by the cautious moderation of all his general doctrines: and, indeed, all his perspicuity, and all his neatness of manner in exhibiting simple truths, were necessary to create a relish for moderation and caution, after the brilliant prospects of systematic knowledge to which the students had been accustomed by Dr. Cullen, his celebrated predecessor. But Dr. Black had no wish to form a medical school, distinguished by some all-comprehending doctrine: he satisfied himself with a clear account of as much of physiology as he thought founded on good principles, and a short sketch of such general doctrines as were maintained by the most eminent authors, though perhaps on a less firm foundation. He then endeavoured to deduce a few canons of medical practice, and concluded with certain rules founded on successful practice only, but not deducible from the principles of physiology previously laid down. With his medical lectures he does not appear to have been himself entirely satisfied: he did not encourage conversation on the different topics, and no remains of these lectures were to be found among his papers. The preceding account of them was given to Professor Robison by a surgeon in Glasgow, who attended the two last medical courses which Dr. Black ever delivered.
Dr. Black’s reception at Glasgow by the university was in the highest degree encouraging. His former conduct as a student had not only done him credit in his classes, but had conciliated the affection of the professors to a very high degree. He became immediately connected in the strictest friendship with the celebrated Dr. Adam Smith—a friendship which continued intimate and confidential through the whole of their lives. Both were remarkable for a certain simplicity of character and the most incorruptible integrity. Dr. Smith used to say, that no one had less nonsense in his head than Dr. Black; and he often acknowledged himself obliged to him for setting him right in his judgment of character, confessing that he himself was too apt to form his opinion from a single feature.