ANNALS

OF

PHILOSOPHY.

MAY, 1815.

ARTICLE I.

Biographical Account of Joseph Black, M. D. F. R. S. E. &c. Professor of Chemistry in the University of Edinburgh.

By Thomas Thomson, M. D. F. R. S.

THE materials from which the following account was drawn were first given to the public in the preface to Dr. Black's lectures, edited by Professor Robison. Mr. Robison informs us that he was indebted for most of his facts" to a paper read to the Royal Society of Edinburgh by the near relation of Dr. Black, Dr. Adam Ferguson, Professor of Mathematics in the University, and well known in the republic of letters by works of the very first rank."

Dr. Joseph Black was born in France on the banks of the Garonne in the year 1728. His father, Mr. John Black, was a native of Belfast, in Ireland, but of a Scotch family, which had been some time settled there. Mr. Black resided for the most part at Bourdeaux, where he carried on the wine trade. He married a daughter of Mr. Robert Gordon, of Hilhead, in Aberdeenshire, who was also engaged in the same trade at Bourdeaux.

The mother of Dr. Black, and the mother of Mr. James Russel, Professor of Natural Philosophy in the University of Edinburgh, were sisters; and the mother of Dr. Adam Ferguson was their aunt, a circumstance which was the origin, though not the cement, of a friendship subsisting between them through life.

In the year 1740 young Black, then in the 12th year of his age, was sent to Belfast, that he might have the education of a British subject. After finishing his grammar school education, he went, in 1746, to the University of Glasgow. Dr. Cullen had commenced his great literary career, and having made choice of philosophical VOL. V. N° V.

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chemistry as a field still untrodden, was delivering lectures upon that science in the University of Glasgow. These lectures caught the congenial fancy of young Black, who speedily became a zealous chemist, and the favourite pupil and friend of his master. Mr. Black had made choice of medicine as the profession to which he proposed to attach himself; and in 1750 or 1751 he went to the University of Edinburgh to finish his medical studies. Here he lived in the house of his cousin German, Mr. James Russel, Professor of Natural Philosophy, in whose society he must have passed his time both agreeably and profitably.

At this period the opinions of the medical professors were divided about the manner in which certain lithontriptic medicines acted in alleviating the excruciating pains of the stone. One of these medicines was lime-water. They all belonged to the class of bodies called caustic, and their efficacy was ascribed to this causticity. Now this causticity was always induced, either directly or indirectly, by the fire. Thus lime-stone in its natural state possesses no caustic properties; but by exposure to a strong heat it is converted into the caustic substance called quick-lime. The investigation of the nature and cause of this causticity was considered as very important. It drew the particular attention of Mr. Black. He investigated the subject with his accustomed precision and coolness; and having ascertained it in a satisfactory manner, made it the subject of his inaugural dissertation in 1754, when the degree of Doctor of Medicine was conferred upon him by the University of Edinburgh, Next year he published his experiments upon magnesia alba, quicklime, and other alkaline substances, in which the whole subject was developed at length.

Just at this time Dr. Cullen was removed to Edinburgh, and the chemical chair in Glasgow became vacant. Dr. Black's experiments on magnesia and quick-lime, which afforded by far the finest specimen of chemical investigation hitherto offered to the public, secured him that chair. Accordingly he was appointed Professor of Anatomy, and Lecturer on Chemistry, in the University of Glasgow. Not considering himself as sufficiently qualified for the anatomical class, he exchanged tasks with the Professor of Medicine. While in Glasgow, therefore, his lectures on the institutes of medicine constituted his chief task. He engaged likewise in the practice of medicine; and from the sweetness of his manners, and the goodness of his heart, soon became a favourite practitioner.

While in Glasgow, he brought to maturity his speculations concerning heat, which had occupied his attention from the very commencement of his medical studies. They constitute one of the most important additions ever made to science, and furnish the most delightful proofs of the wisdom and beneficence of the Author of nature.

Dr. Black continued in the University of Glasgow from 1756 to 1766. In that year Dr. Cullen, Chemical Professor in Edinburgh, was appointed Professor of Medicine, and thus a vacancy was made

in the chemical chair of that University. There was but one wish with respect to a successor. Indeed, when the vacancy happened in 1756, by the death of Dr. Plummer, Dr. Black's reputation stood so high, that, had it depended on the University, he would have been appointed to the chair. He had now greatly added to his claim of merit by his important discovery of the procedure of Nature in producing fluidity and vapour; and he had acquired the high esteem of every one by the singular moderation and scrupulous caution which marked all his researches. Dr. Black was appointed to the chemical chair of Edinburgh, to the general satisfaction of the public; but the University of Glasgow sustained an irreparable loss. In this new scene his talents were more conspicuous, and more extensively useful. The number of his pupils underwent a progressive and annual increase during the whole time that he was Professor. Many of these pupils were from the workshop of the artist or manufacturer, and had not enjoyed the advantage of a liberal education. Yet such persons, in the opinion of Dr. Black, constituted by no means the least important part of his class. He laboured, therefore, with the greatest assiduity, to bring his lectures to a level with this least informed part of his audience; and thus every year he rendered them more and more elementary. His lectures were always listened to by his audience with inexpressible delight. His voice was low; but sweet and distinct. His language was simplicity itself; but always apposite, and never vulgar. His experimental illustrations were exactly suited to the object in view, and carried full conviction to the mind of the spectator: there was no glare, no parade, no showman exhibition; but an attic elegance and simplicity highly delightful to a refined and cultivated mind. I describe the lectures such as I listened to them myself, about the year 1796. But at that period Dr. Black's vigour was nearly gone. Indeed his state of health was such that he was obliged to employ an assistant to help him in his experiments, and to lecture for him occasionally. But even with all these disadvantages, the effects of his lectures were such as I can never forget: they made an impression on my mind which no time can efface.

Dr. Black's health had been always delicate. The least exertion brought on a cough, with a spitting of blood. This obliged him to remain a tranquil spectator of the chemical discoveries which were constantly pouring in from all quarters, and to leave it to others to explore the tempting fields which he had originally laid open. Towards the latter period of his life, when undue advantages were taken by certain foreigners of the discoveries which he had made, without any acknowledgment of obligations to the original discoverer, he was urged by his friends to lay an historical detail of the whole of his labours before the public. He began this task more than once; but was always obliged to desist almost immediately, in consequence of the illness brought on by this unusual exertion of thought.

By abstaining from all exertion, by living in the most abstemious manner, and by constant, though moderate exercise, he contrived to enjoy an almost uninterrupted, though feeble state of health, and to prolong his life to a considerable old age, happy to the last day, and capable of enjoying the conversation of a few select friends. His only apprehension was that of a long continued sick bed; and this perhaps less from any selfish feeling than from the humane eonsideration of the trouble and distress occasioned to attending friends; and never was this modest and generous wish more completely gratified. "On the 26th Nov. 1799, and in the 71st year of his age, he expired without any convulsion, shock, or stupor, to announce or retard the approach of death. Being at table with his usual fare some bread, a few prunes, and a measured quantity of milk diluted with water; and having the cup in his hand when the last stroke of his pulse was to be given, he set it down on his knees, which were joined together, and kept it steady with his hand in the manner of a person perfectly at ease; and in this attitude expired, without spilling a drop, and without a writhe on his countenance; as if an experiment had been required to show to his friends the facility with which he departed. His servant opened the door to tell him that some one had left his name, but getting no answer, stepped about half way towards him, and seeing him sitting in that easy posture, supporting his bason of milk with one hand, he thought that he had dropped asleep, which he had sometimes seen happen after his meals. He went back and shut the door; but before he got down stairs some anxiety, which he could not account for, made him return and look again at his master. Even then he was satisfied, after coming pretty near him, and turned to go away; but again returning, and coming quite close to him, he found him without life.

"So ended a life which had passed in the most correct application of reason and good sense to all the objects of pursuit which Providence had prescribed to his lot, with many topics of agreeable recollection, and few things to ruffle his thoughts. He had long enjoyed the tender and affectionate regard of parents whom he loved, honoured, and revered; with the delightful consciousness of being a dutiful son, and being cherished as such-one of a family remarkable for sweetness of disposition and manners, he had lived with his brothers and sisters in terms of mutual love and attachment. He had never lost a friend, but by the stroke of mortality, and he felt himself worthy of that constancy of regard. He had followed a profession altogether to his taste and had followed it in a manner, and with a success, which procured him the esteem and respect of all competent judges, and set his name among the most eminent; and he was conscious that his reputation was not unmerited; and with a success in point of emolument which secured the respect even of the ignorant; which gave him the command of every rational gratification, and enabled him to add greatly to the

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comforts of the numerous descendants of his worthy parents-heirs, not only of their name, but likewise of their unambitious moderation and amiable simplicity of character."

The publications of Dr. Black (omitting his inaugural dissertation) amount ouly to three short papers; for respecting his discoveries and speculations concerning heat, he published no account at all. In the year 1803, or three years after his death, his lectures were published by Dr. John Robison, Professor of Natural Philosophy in the University of Edinburgh, who undertook the task of editor at the request of Dr. Black's friends. They appear to me to be a pretty fair representation of his lectures such as they were about the year 1796; and though it was by no means doing justice to Dr. Black to give to the world lectures never intended for publication, and just at a period too when the science had assumed a new form, quite different from that under which he had been accustomed to view it; yet they convey a very happy view of the elegant simplicity of manner by which he was distinguished, of the very apt illustrations by which the different subjects that he treated were elucidated, and of the true philosophical caution with which all his conclusions were drawn.

His Experiments upon Magnesia Alba, Quick-Lime, and other Alkaline Substances, were published in 1755, and constitute in my opinion one of the very best specimens of analytical investigation ever offered to the public. It was known that when lime-stone is exposed to a violent heat for a sufficient time, it is converted into quick-lime, a substance which has a strong caustic taste, gives a green colour to vegetable blues, corrodes animal and vegetable substances, &c. If pearl ash be mixed with three or four times its weight of quick-lime, and agitated for some hours in a quantity of water, the quick-lime is converted into chalk, and the pearl-ash becomes exceedingly caustic and corrosive. These facts were suffi ciently known; but no satisfactory explanation of them had been offered, though it was generally believed that the fire had imparted something to the lime to which it was indebted for its causticity, Dr. Black demonstrated, by the most decisive experiments, that lime-stone is a compound of two substances; namely, quick-lime and a peculiar species of air which acts the part of an acid, and to which he gave the name of fixed air. The fire disengages this air, and drives it off. The quick-lime remains in a state of purity, and exhibits its natural caustic properties. Pearl-ash is in like manner a compound of pure potash and fixed air. Quick-lime has a stronger affinity for fixed air than potash has. Accordingly it separates the fixed air from the alkali, and is converted into lime-stone; while the alkali, thus freed from the acid with which it was united, exhibits its natural caustic properties in all their energy. Such is the outline of the theory which-Dr. Black establishes in his dissertation. He establishes likewise the peculiar properties of magnesia, and shows that it differs from every other earthy body.