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 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 he 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, be 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, 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 lost, 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
chemica1 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, found 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.
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