A biographical dictionary of eminent Scotsmen/Black, Joseph

BLACK, Joseph, M.D. "the illustrious Nestor (as he has been termed by Lavoisier) of the chemical revolution,"—was not a native of Scotland, having been born on the banks of the Garonne, in France; but as his father was of Scottish extraction, while his mother was a native of that country, and as Scotland, further, was the scene not only of the better part of his life, but of all those exertions in science which will transmit his name to posterity, it seems proper that he should obtain a place in this work, even at the expense of a slight violation of its leading principle.

John Black, the father of the illustrious subject of this memoir, was a native of Belfast, descended, as already mentioned, from a Scottish family, which had for some time been settled there. For the purpose of carrying on the profession of a wine-merchant, he resided chiefly at Bourdeaux, where he married a daughter of Mr Robert Gordon of Hillhead in Aberdeenshire; a gentleman who also resided at Bourdeaux, and was engaged in the same trade. The sister of Mrs Black was mother to Mr Russel, professor of natural philosophy in the university of Edinburgh, and their aunt was mother to Dr Adam Ferguson, professor of moral philosophy in the same college, and author of the History of the Roman Republic. While Mr John Black resided at Bourdeaux, he was honoured with the friendship of Montesquieu, who was president of the parliament or court of justice in that province. "My father," says Dr Black, "was honoured with President Montesquieu's friendship, on account of his good character and virtues. He had no ambition to be very rich; but was cheerful and contented, benevolent and liberal-minded. He was industrious and prudent in business, of the strictest probity and honour, very temperate and regular in his manner of life. He and my mother, who was equally domestic, educated thirteen of their children, eight sons and five daughters, who all grew up to men and women, and were settled in different places. My mother taught her children to read English, there being no school for that purpose at Bourdeaux." The regard which Montesquieu entertained for Mr Black was testified in the warmest terms, when the latter was proposing to return to his native country. "I cannot," said he, on that occasion, "be reconciled to the thoughts of your leaving Bourdeaux. I lose the most agreeable pleasure I had, that of seeing you often, and forgetting myself with you."

Dr Black was born in the year 1728. In 1740, a few years before his father retired from business, he was sent home, in order to have the education of a British subject. After spending some time at the schools of Belfast, he was sent, in 1746, to complete his studies at the college of Glasgow. Here his attention became decidedly fixed upon physical science; insomuch that, on being desired to select a profession, he chose that of medicine, on account of its allowing the greatest scope for such studies. It was about this time that Dr Cullen had been appointed lecturer on chemistry in Glasgow university. Hitherto this science had been only treated as a curious, and, in some respects, a useless art. This great man, conscious of his own strength, and taking a wide and comprehensive view, saw the unoccupied field of philosophical chemistry open before him. He was satisfied that it was susceptible of great improvement, by means of liberal inquiry and rational investigation. It was perhaps the good fortune of Dr Black, in falling under such a master, that gave his mind a peculiar bent in favour of this department of physical science. His previous acquirements and extraordinary aptitude speedily became known to Dr Cullen, who was at all times remarkable for the personal attentions he paid to his pupils. Black became a valuable assistant to Dr Cullen in his chemical operations, and his experiments were sometimes publicly adduced in the lecture, as a sufficient authority for various new facts. Thus commenced a friendship between two great men, which was never afterwards interrupted, except by the Great Divider of kindred minds and loving hearts, and which was of considerable service to mankind.

In 1751, Black was sent to Edinburgh to complete the course of his medical studies. At this time, the mode of action of lithotriptic medicines, but particularly lime water, in alleviating the pains of stone and gravel, divided the opinions of professors and practitioners. This subject attracted the attention of Black, and it appears from some of his memorandums, that he at first held the opinion, that the causticity of alkalis was owing to the igneous matter which they derive from quick lime. Having prosecuted his experiments on magnesia, the grand secret of nature, which for ever will be associated with his name, was laid open to him. He perceived that the acrimony of these substances was not owing to their combination with igneous particles; that it was their peculiar property; and that they lost this property, and became mild, by combining with a certain portion of air, to which ha gave the name of fixed air; because it was fixed or become solid in the substances, into the composition of which it entered. He discovered, for instance, that a cubic inch of marble consisted of half its weight of pure lime, and a quantity of air equal to six gallons measure. This grand discovery, which forms one of the most important eras of chemical science, was the subject of his inaugural essay, on obtaining his degree as doctor of medicine; and the reputation it acquired for him, was the means, in 1756, of placing him in the chair of chemistry at Glasgow, then vacated by Dr Cullen, who was transferred to the same chair in the college of Edinburgh. The theory of fixed air (now termed by chemists, carbonic acid gas,) was speedily propagated on the continent, where at this time chemistry was occupying the attention of many great men. In Germany, Dr Black's opinions, though placed on the firmest basis by experiments, met with much opposition, which, it appears, gave him an uneasiness not to have been expected from his philosophical, and rather indolent character. In France, however, he was very differently treated. Lavoisier, in sending him a copy of his treatise on respiration, thus expressed himself: "It is but just you should be one of the first to receive information of the progress made in a career which you yourself have opened, and in which all of us here consider ourselves your disciples." To this Black replied, with a just admiration of what the French chemists were doing, and without reference to any merit of his own.

On his assuming the chair of chemistry at Glasgow, that of anatomy was also imposed upon him; but this latter he soon exchanged for that of medicine, for which, it would appear, he was better qualified. He gave great satisfaction by the perspicuity and simplicity, the caution and moderation, which he discovered in his medical lectures. At the same time, he became a favourite practitioner in the city, where his engaging appearance and manners, and the benevolent and unaffected interest which he took in all the cases entrusted to his care, rendered him a most welcome visitor in every family. His principal friend at Glasgow was his associate Dr Adam Smith, professor of moral philosophy, with whom he had become intimate, when attending the university as a student A peculiar simplicity and sensibility, an incorruptible integrity, the strictest delicacy and correctness of manners, marked the character of each of the philosophers, and firmly bound them in the closest union.

"It seems to have been between the year 1759 and 1763,^[1] that his speculations concerning heat, which had long occupied his thoughts, were brought to maturity. And when it is considered by what simple experiments, by what familiar observations, Dr Black illustrated the laws of fluidity and evaporation, it appears wonderful that they had not long before been observed and demonstrated. They are, however, less obvious than might at first sight be imagined, and to have a distinct and clear conception of those seemingly simple processes or nature, required consideration and reflection. If a piece of wood, a piece of lead, and a piece of ice, are placed in a temperature much inferior to that of the body; and if we touch the piece of wood with the hand, it feels cold; if we touch the piece of lead, it feels colder still; but the piece of ice feels colder than either. Now, the first suggestion of sense is, that we receive cold from the wood; that we receive more from the lead; and most of all from the ice; and that the ice continues to be a source of cold till the whole be melted. But an inference precisely the contrary to all this is made by him, whose attention and reflection has been occupied with this subject. He infers that the wood takes a little heat from the hand, but is soon heated so much as to take no more. The lead takes more heat before it be as much satiated; and the ice continues to feel equally cold, and to carry off heat as fast as in the first moment, till the whole be melted. This, then, was the inference made by Dr Black.

"Boerhaave has recorded an interesting observation by Fahrenheit, namely, that water would sometimes grow considerably colder than melting snow without freezing, and would freeze in a moment when shaken or disturbed; and in the act of freezing give out many degrees of heat. Founded on this observation, it appears that Dr Black entertained some vague notion or conjecture, that the heat which was received by the ice, during its conversion into water, was not lest, but was still contained in the water. And he hoped to verify this conjecture, by making a comparison of the time required to raise a pound of water one degree in its temperature, with the time required to melt a pound of ice, both being supposed to receive the heat equally fast. And that he might ascertain how much heat was extricated during congelation, he thought of comparing the time required to depress the temperature of a pound of water one degree, with the time required for freezing it entirely. The plan of this series of experiments occurred to him during the summer season. But for want of ice, which he could not then procure, he had no opportunity of putting them to the test. He therefore waited impatiently for the winter. The winter arrived, and the decisive experiment was performed in the month of December 1761. From this experiment it appeared that as much heat was taken up by the ice, during its liquefaction, as would have raised the water 140 degrees in its temperature, and on the other hand, that exactly the same quantity of heat was given out during the congelation of the water. But this experiment, the result of which Dr Black eagerly longed for, only informed him how much heat was absorbed by the ice during liquefaction, was retained by the water while it remained fluid, and was again emitted by it in the process of freezing. But his mind was deeply impressed with the truth of the doctrine, by reflecting on the observations that presented themselves when a frost or thaw happened to prevail. The hills are not at once cleared of snow during the sunshine of the brightest winter day, nor were the ponds suddenly covered with ice during a single frosty night Much heat is absorbed and fixed in the water during the melting of the snow; and on the other hand, while the water is changed into ice, much heat is extricated. During a thaw, the thermometer sinks when it is removed from the air, and placed in the melting snow; and during severe frost, it rises when plunged into freezing water. In the first case, the snow receives heat; and in the last, the water allows the heat to escape again. These were fair and unquestionable inferences, and now they appear obvious and easy. But although many ingenious and acute philosophers had been engaged in the same investigations, and had employed the same facts in their disquisitions, those obvious inferences were entirely overlooked. It was reserved for Dr Black to remove the veil which hid this mystery of nature, and by this important discovery, to establish an era in the progress of chemical science, one of the brightest, perhaps, which has yet occurred in its history."

Dr Black explained his theory of latent heat—such was the name he himself gave to it—to the members of a literary society, April 23, 1762, and afterwards laid before his students a detailed view of the extensive and beneficial effects of this habitude in the grand economy of nature. From observing the analogy between the cessation of expansion by the thermometer, during the liquefaction of the ice, and during the conversion of water into steam, Dr Black, having explained the one, thought that the phenomena of boiling and evaporation would admit of a similar explanation. He was so convinced of the truth of this theory, that he taught it in his lectures in 1761, before he had made a single experiment on the subject At this period, his prelections on the subject of evaporation were of great advantage to Mr James Watt, afterwards so distinguished for his application of steam power. His discovery, indeed, may be said to have laid the foundation of that great practical use of steam, which has conferred so immense a blessing upon the present age.

In 1766, on Dr Cullen being removed from the chair of chemistry at Edinburgh, to that of medicine, Dr Black, as formerly, supplied the vacant place. In this new scene, he saw that his talents would become more conspicuous, and of more extensive utility. He was therefore encouraged to devote himself, with still more enthusiastic zeal, to his duties as a chemical teacher. In this he was so far successful, that chemistry at length became a fashionable study in the Scottish capital, and a necessary part of the education of every gentleman. After this period, however, he retired from the field of chemical research, which now began to be occupied by a great number of distinguished philosophers. The cause of this was the delicate state of his health, aided, perhaps, a little by that indolence, or rather perhaps absence of ambitious motive, which has been already alluded to. It is to be regretted that, for the same reason, he can scarcely be said to have published any thing to the world, by which his discoveries might be permanently secured to the honour of his own name. From the period of his accession to the chemical chair at Edinburgh, he was, for thirty years, a most distinguished member of the professional society, which then adorned the capital, and has since given such an Augustan eclat to the latter age of the eighteenth century. Whatever obstruction his health proved in the way of publishing, it never marred the active discharge of his duties. His courses became every year plainer and more familiar, and were attended by a larger number of pupils. The simplicity and elegance of his experiments were always much admired. His manner and appearance were peculiarly pleasing. His voice in lecturing was low and fine, and his articulation so distinct that it was perfectly well heard by a large audience. His discourse was remarkable for plainness and perspicuity; all his illustrations, whether by experiment, or by reference to the processes of nature, were quite apposite; his hearers rested with the most entire confidence on his conclusions, and even the most illiterate could not mistake his sentiments.

Dr Black's conduct in private life was marked by a striking degree of decorum, without the slightest approach to formality. His habit of studying physical science rendered him very much a man of facts and demonstrations; he is said to have been so entirely destitute of fancy, or to have so effectually repressed that faculty, that he never was known to utter a joke. In his domestic affairs, he was rigidly frugal and methodical; yet his house was open to an enlightened hospitality, in which he enjoyed as much of the society of his friends as his delicate health would permit. His chief friends were Smith, Hume, Carlyle, Home, and Hutton. The last was closely connected with him in philosophical pursuits, as well as in the bonds of private friendship—notwithstanding that there were some striking points of difference between the two men. In the latter days of Dr Black, he sunk into a low state of health, and only preserved himself from the shocks of the weather in this variable climate by a degree of care almost fantastic. Thus he spun out the thread of life to the last fibre. It was his generous and manly wish that he might never live to be a burden to his friends; and never was the wish more completely gratified. On the 26th of November, 1799, and in the seventy-first 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 the pulse was to be given, he had set it down upon 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 in 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 basin of milk with one hand, he thought that he had dropped asleep, which he had sometimes seen happen after his meals. The man went back and shut the door, but before he got down stairs, some anxiety that he could not account for, made him return, and look again at his master. Even then, he was satisfied, after coming pretty near, and turned to go away, but again returned, and coming quite close, fount! his master without life. Dr Black, who had never been married, left more money than any one had thought he could have acquired in the course of his career. It was disposed of by his will in a manner highly characteristic. Being divided into ten thousand shares, it was parcelled out to a numerous list of relations in shares, in numbers, or fractions of shares, according to the degree in which they were proper objects of his care or solicitude.

1. The following most interesting account of one of the principal discoveries in modern science is from a biographical memoir, prefixed by professor Robison to Dr Black's lectures.

Joseph Black, M.D.
 

professor of chemistry, university of glasgow.