In 1788, he went to Virginia,
as tutor to two young college friends, Messrs Randolph; and after spending
more than a year in America, returned to Edinburgh. In January 1790, he
proceeded to London, carrying with him some recommendatory letters from Dr
Smith; he has been heard to mention, that one of the most pressing
injunctions with which he was honoured by that illustrious philosopher, was
to be sure, if the person to whom he was to present himself was an author,
to read his book before approaching him, so as to be able to speak of it, if
there should be a fit opportunity. His first intention was to deliver
lectures on natural philosophy; but being disappointed in his views, he
found it expedient to commence writing for periodical works, as the readiest
means of obtaining subsistence. For obtaining employment of this kind, he
was mainly indebted to his friend Dr William Thomson, who engaged him upon
the notes of a new edition of the Bible, which he was then publishing in
numbers. About three months after his arrival in London, he made an
agreement with Mr Murray, the bookseller, to translate Buffon’s Natural
History of Birds, which was published in 1793, in nine octavo volumes. The
sum he received for it laid the foundation of that pecuniary independence
which, unlike many other men of genius, his prudent habits fortunately
enabled him early to attain. The preface to this work, which was published
anonymously, is characterised by all the peculiarities of his later style;
but it also bespeaks a mind of great native rigour and lofty conceptions,
strongly touched with admiration for the sublime and the grand in nature and
science. During the progress of the translation, he fulfilled an engagement
with the Messrs Wedgewood of Etruria in Staffordshire, to superintend their
studies; he left them in 1792. In 1794, Mr Leslie spent a short time in
Holland; and, in 1796, he made the tour of Germany and Switzerland with Mr
Thomas Wedgewood, whose early death he ever lamented as a loss to science
and his country. About this period, he stood candidate for a chair at St
Andrews, and subsequently, for that of natural philosophy in Glasgow, but
without success. The fortunate candidate on the latter occasion was Dr James
Brown of St Andrews, with whom Mr Leslie to the end of his life maintained a
constant intimacy. In 1799, he travelled through Norway and Sweden, in
company with Mr Robert Gordon, whose friendship he had acquired at St
Andrews college.
At what period Mr Leslie
first struck into that brilliant field of inquiry where he became so
conspicuous for his masterly experiments and striking discoveries regarding
radiant heat, and the connexion between light and heat, we are unable to
say. But his Differential Thermometer—one of the most beautiful and delicate
instruments that inductive genius ever contrived as a help to experimental
inquiry, and which rewarded its author by its happy ministry to the success
of some of his finest experiments—must have been invented before the year
1800, as it was described in Nicholson’s Philosophical Journal some time
during that year. The results of those fine inquiries, in which he was so
much aided by this exquisite instrument, were published to the world in
1804, in his celebrated "Essay on the Nature and Propagation of Heat."
[Previous to this period, Mr Leslie, when not otherwise or elsewhere
engaged, used to live with his brothers at Largo; and there were the
experiments for his essay on heat carried on, and the book written.] The
experimental devices and remarkable discoveries which distinguish this
publication, far more than atone for its great defects of method, its very
questionable theories, and its transgressions against that simplicity of
style which its aspiring author rather spurned than was unable to exemplify;
but which must be allowed to be a quality peculiarly indispensable to the
communication of scientific knowledge. The work was honoured, in the
following year, by the unanimous adjudication to its author, by the council
of the Royal Society, of the Rumford Medals, appropriated to reward
discoveries in that province, whose nature and limits he had so much
illustrated and extended.
Mr Leslie thus distinguished
himself by his acquirements, when, early in 1805, in consequence of the
translation of professor Playfair from the chair of mathematics to that of
natural philosophy in the university of Edinburgh, the former became vacant,
and the subject of this memoir appeared as a candidate for the situation. It
might have been expected that, where the qualifications of the individual
were so decidedly above all rivalry, there could have been no hesitation in
his native country to confer upon him the honour which he sought. Such there
might not have been, if what is called the moderate party in the Scottish
church, had not been inspired by a jealousy of his liberal principles in
politics, accompanied by a desire of advancing one of their own number, to
oppose his election. The person brought forward as the rival candidate was
Dr Thomas Macknight, one of the ministers of the city, and son of the
venerable commentator on the Epistles,--a gentleman highly qualified, no
doubt, not only for this, but for almost any other chair in the university;
but who, nevertheless, could not be matched against an individual so
distinguished for the benefits he had conferred on science as Mr Leslie; and
who was moreover liable to the disqualifying consideration that he was
already engaged in an office which, to be well done, requires the whole man,
while Mr Leslie stood in the light of a most useful member of society in a
great measure unprovided for.
The electors in this case
were the magistrates and town-council of Edinburgh, and to them Mr Leslie
was recommended not only by fame, but by the warmest testimonials from Sir
Joseph Banks, Mr Dempster of Dunnichen, Dr Hutton of Woolwich, Baron
Masseres, and Dr Maskelyne. In the supposition that these men were disposed
to discharge their trust with fidelity, they could have no hesitation in
preferring Mr Leslie; and it is to be related to their credit, that they had
no such hesitation. On learning the bent of their resolution, the ministers
of Edinburgh held various private meetings, as if to indicate the more
pointedly that they had a peculiar interest of their own in the matter; and
it was resolved to oppose Mr Leslie’s election on the grounds of what they
deemed an infidel note in his essay on heat; employing for this purpose a
clause in the fundamental charter of the college, directing the magistrates
to take the advice of the Edinburgh clergy in the election of professors.
The note alluded to was one
in reference to the unphilosophical theories which once attempted to explain
the phenomena of gravitation by means of invisible aethers. Mr Leslie, in
treating this point, found it convenient to refer to Mr Hume’s theory of
cause and effect, in which, as is well known, he makes use of certain
generally received doctrines to invalidate the argument for the existence of
the Deity. In making the reference, it did not seem to Mr Leslie to be
necessary that he should condemn the ultimate use made of these doctrines by
Mr Hume, since he was only engaged in a physical examination. His note,
therefore, stands as follows: "Mr Hume is the first, so far as I know, who
has treated of causation in a truly philosophic manner. His Essay on
Necessary Connexion seems a model of clear and accurate reasoning. But it
was only wanted to dispel the cloud of mystery which had so long darkened
that important subject. The unsophisticated sentiments of mankind are in
perfect unison with the deductions of logic, and imply at bottom nothing
more in the relation of cause and effect, than a constant invariable
sequence." From these words, however, it was evident, in the opinion of his
clerical opponents, "that Mr Leslie, having, with Mr Hume, denied all such
necessary connexion between cause and effect, as implies an operating
principle in the cause, has, of course, laid a foundation for rejecting all
argument that is derived from the works of God, to prove either his being or
attributes."
When Mr Leslie was informed
of the grounds on which the Edinburgh ministers rested their opposition, he
addressed a letter to the Rev. Dr Hunter, professor of divinity, and one of
the few clergymen of the city who were not opposed to him, laying before him
some explanations of the note, to which he begged him to call the attention
of his brethren. These explanations were chiefly what are stated above, and
are thus followed up: "I have the fullest conviction that my ideas on the
question to which the note refers, would appear to coincide, in every
essential respect, with those of the most enlightened adversaries of Mr
Hume’s philosophy. But, limited as I am to a few moments of time, I can only
disavow (which I do with the greatest sincerity and solemnity,) every
inference which the ingenuity of my opponents may be pleased to draw from
the partial view I have taken of the general doctrine, to the prejudice of
those evidences on which the truths of religion are founded. If I live to
publish another edition of my work, I pledge myself to show in an additional
paragraph, how grossly and injuriously I have been treated on this occasion.
* * * It is painful to be called on, after the habits of intimacy in which I
have lived with the most exemplary characters in both parts of the island,
to repel a direct charge of atheism; but whatever may be the effect of such
calumnies on the minds of strangers, it affords me much consolation to
think, that they will be heard with contempt and indignation by those who
know the real state of my sentiments, and particularly by such as are
acquainted with the strictness of those religious principles in which I had
the happiness to be educated from my earliest years."
This letter was laid before
the ministers at a meeting held by them on the 12th of March (1805); but
being, to use their own phrase, by no means satisfied with it, they
appointed a committee, consisting of Dr Grieve, Mr David Black, Mr David
Dickson, and Dr Inglis, to proceed to the town-council and protest against
the election of Mr Leslie. As the council was to be that day engaged in the
election, the committee went accordingly to their chamber, and presented a
protest which had been prepared, in which, besides stating the grand
objection of the note and their inferences from it as to Mr Leslie’s
religious principles, they stated that, "in the event of his being elected,
notwithstanding this representation, they reserved to themselves full power
of questioning the validity (if such election, and of employing whatever
means may, to them, be found competent for preventing Mr Leslie’s induction
into the office of professor; with full power, in the event of his
induction, to prosecute for his ejection from said office in any competent
court, civil or ecclesiastical." Immediately after this paper was given in
and its bearers had left the hall, the council elected Mr Leslie.
At the meeting of the
presbytery of Edinburgh on the 27th, the committee of the city clergy gave
in a representation stating these transactions, along with a copy of their
protest, and requested the reverend court to take such steps in the matter
as they might judge proper. It was here determined by vote to carry the
affair before the synod; a step formally necessary for bringing it under the
decision of the highest national church court, the general assembly.
At the meeting of this court,
on the 22nd of May, the case of Mr Leslie came before it in the shape of a
complaint by the Rev. Sir Henry Moncrieff and other members of the synod,
against the reference of the case to the general assembly. It was thus
apparent that the leaders of the more zealously pious party of the church
had taken the part of Mr Leslie against their accustomed opponents. The
interest which the public could not have failed to entertain respecting the
question, even if confined to its native merits, was excited to an uncommon
degree by this complication of the phenomenon. The case, nevertheless,
furnished only an unusually striking example of what must always be the
result of a party system in any deliberative body. It happened to be
convenient for the "moderate" party on this particular occasion, to show an
anxious desire for the purity of faith and doctrine; and for this purpose
they raked up a negative title in the Edinburgh clergy to be consulted in
the exercise of the town-council patronage, which had not been acted upon
for twenty-six years, during which time several of the very men now
prosecuting had been elected to chairs in the university without regard to
it. It was equally convenient for the evangelical party, though adverse to
all their usual principles, to regard the suspected infidelity of Mr Leslie
with a lenient and apologetic spirit, in order that they might be in their
usual position regarding their opponents, and because they hoped to gain a
triumph for themselves in the non-success of a prosecution, which they could
easily see rested upon no valid grounds, and could hardly, in the face of
public opinion, be carried to its utmost extent, even though a majority of
servile votes could have been obtained for the purpose.
In the course of the long
debate which followed the introduction of the case, some very strong
testimonies were brought forward in favour of Mr Leslie’s moral and
religious character. A letter from the minister of Largo testified that,
during the two past years, while Mr Leslie resided in the parish, he had
paid a becoming respect to religion, and that, if great abilities highly
improved, an unstained moral character, and a tender discharge of every
filial duty, recommend to confidence and esteem, these belonged to him.
Another letter, from the clergyman of the neighbouring parish, after
remarking that insinuations of the kind disseminated respecting Mr Leslie,
yielded but a contemptible support to any cause, stated the following
particulars: "I have lived in habits of intimacy with Mr Leslie for some
time past; I have had an opportunity of knowing his religious and political
sentiments; I have been furnished, in short, with satisfactory evidence of
his attachment to our ecclesiastical and civil establishment. His father
officiated long as a worthy elder of our church: his son was once a student
of divinity; and though he has not prosecuted his theological studies,
having been much engaged in other literary pursuits, I never heard that he
had ceased to respect the doctrines or discipline of the church of Scotland.
On the contrary, the leading doctrines of Christianity he regards with
reverence."
‘There was also read a letter
from Mr Leslie to a friend, of date, February 22nd, 1805, in which he thus
expressed himself: "It was my lot to receive a most virtuous and religious
education, in the bosom of a family eminently distinguished by its exemplary
lives; and the impressions of my early years, no distance of time, or change
of circumstances can ever efface. If my mind is more enlarged by culture, I
have likewise learned to see more deeply the importance of those truths
which bind men together in society, and which, visiting their inmost
recesses, appal the guilty and hold forth comfort to the wretched. I have
ever been a sincere lover of peace, of decency, and good order. My time has
been almost wholly spent in abstract researches, and the study of the
sublime operations of nature. The questions, so much agitated of late,
served with me only to amuse a few leisure moments; and even at that
eventful period, when the minds of men, and particularly of young men, were
so violently inflamed, I escaped in a great measure the contagion. I sighed,
indeed, for the improvement of our species; but the slightest appearance of
tumult, or popular violence, was most abhorrent to my temper. I never had
the remotest connexion with any party or political association whatever. In
the spirit of mildness, I endeavoured to think and act for myself. My
sentiments of loyalty had been confirmed by what I had seen during a short
stay in America, where I witnessed the disgusting and pernicious influence
assumed by an ignorant, licentious, and dissolute rabble. * * It is our
native island that presents the truly cheering picture of equal laws mildly
administered, and holds up a body of religious institutions at once
rational, decent, and impressive. I venerate the great principles of our
Christian faith, and am solicitous to mark, by my external behaviour, that
respect which I cherish. Raising my affections above this little spot of
earth, the restless scene of intrigue, and strife, and malice, I look
forward with joy and expectation to that better country beyond the grave."
Among the most powerful
speakers on the side of Mr Leslie was Sir Henry Moncrieff, who observed that
the question expressly and simply referred to a civil right of the Edinburgh
ministers. This right, he showed, had never been before exercised in the
election of a professor of mathematics, and in all probability would be
confined by a court of law to the professorships existing at the institution
of the university, of which that of mathematics was not one. The right,
however, if right it was, had in reality been exercised: the clergy had gone
to the council and given their advice, and, though it had not been
followed, still it had been received. Sir Henry also commented in strong
terms upon the fact, that the whole of this prosecution, threatening so much
to Mr Leslie, had been conducted in such a way as to allow him no
possibility of appearing in his own defence. "It is a circumstance," further
continued this nervous orator, "which I cannot help mentioning, that the
ministers of Edinburgh, in their zeal to find any sort of heresy in Mr
Leslie’s note, have unfortunately announced a doctrine in opposition to that
which they would fix on him, which is capable of an interpretation more
hostile to religion than any thing that they have imputed to his book. In
asserting such a necessary connexion between cause and effect as
implies an operating principle in the cause, they express a doctrine
of which I can scarcely mention the pernicious tendency. If the necessity is
applied to the first cause, it is not far from blasphemy. If it is
restricted (as I suppose it was meant to be) to the second cause, it is
substantially the doctrine of materialism, and leads directly to atheism.
(Here Mr Ritchie interrupted the speaker, to remind him that he had
qualified the expression, and restricted his meaning to a conditional
or contingent necessity.) True, sir, he did so. He did the very thing
which he will not allow Mr Leslie to do. He gives an explanation for himself
and his friends, when he perceives the consequences of the original
expressions they had employed. He qualifies the necessity they asserted by
the term ‘conditional,’ by which he means to restrict it, and he expects
that we are to take his explanation without a murmur; although, when Mr
Leslie would confine the assertion in his note to ‘objects of physical
examination,’ he obstinately fixes him down to his original expressions, and
rejects the limitation as utterly inadmissible. Unfortunately, sir, the
doctrine of the ministers of Edinburgh, with regard to such a necessary
connexion between cause and effect as implies an operating principle in the
cause, stands in its original state in the protest which they gave to the
town-council, it is recorded in the council books; and there it must
remain in all future times, without any explanation whatever, be its
tendency or its heresy ever so mischievous.
"The use," he continued with
exquisite sarcasm, "which may be made of incautious expressions, may be as
forcibly illustrated from the protest of the ministers of Edinburgh, as from
the note of Mr Leslie. But there is this material distinction between the
two cases: Mr Leslie, at least, understood the precise meaning of his
assertions, as far as they related to the subject of which he was writing;
but my reverend brethren enunciated their dogma in perfect innocence and
simplicity, completely unconscious of its true import and tendency!"
Near midnight, on the second
day of the debate, it was determined by 96 against 84 to dismiss this
vexatious case without further notice. On the vote being announced, a shout
of applause—an unwonted sound in the general assembly—burst from the crowd
assembled in the galleries.
Mr Leslie entered without
further opposition upon the duties of his chair, and upon a course of
experimental discovery by which he was to confer lustre upon the university.
Through the assistance of one of his ingenious contrivances—his
hygrometer—he arrived in 1810 at the discovery of that singularly beautiful
process of artificial congelation, which enabled him to convert water and
mercury into ice. "We happened," says a brother professor, "to witness the
consummation of the discovery—at least, of the performance of one of the
first successful repetitions of the process by which it was effected; and we
shall never forget the joy and elation which beamed on the face of the
discoverer, as, with his characteristic good nature, he patiently explained
the steps by which he had been led to it."
In 1809 Mr Leslie published
his Elements of Geometry, which immediately became a class-book, and has
since gone through four editions. He also published, in 1813, an "Account of
Experiments and Instruments depending on the relation of Air to Heat and
Moisture." In 1817 he produced his "Philosophy of Arithmetic, exhibiting a
Progressive view of the Theory and Progress of Calculation," a small octavo;
and, in 1821, his "Geometrical Analysis, and Geometry of Curve Lines, being
volume second of a Course of Mathematics, and designed as an Introduction to
the study of Natural Philosophy." In 1822 he published "Elements of Natural
Philosophy," for the use of his class—reprinted in 1829—and of which only
one volume appeared. "Rudiments of Geometry," a small octavo, published,
1828, and designed for popular use, was his last separate work. Besides
these separate works, he wrote many admirable articles in the Edinburgh
Review, three profound treatises in Nicholson’s Philosophical Journal, a few
in the Transactions of the Royal Society of Edinburgh, and several very
valuable articles on different branches of physics in the Supplement to the
Encyclopaedia Britannica. In 1819, on the death of professor Playfair, whose
promotion had formerly made room for him in the chair of mathematics, he was
elevated to the professorship of natural philosophy, by which his powers
were of course brought into a far wider field of display and of usefulness,
than they had been for the preceding fourteen years. Among the preliminary
treatises of the seventh edition of the Encyclopaedia Britannica, which
began to be published in 1830, he wrote a "Discourse on the History of
Mathematical and Physical Science, during the eighteenth century," which may
be described as one of the most agreeable and masterly of all his
compositions.
The income enjoyed by Mr
Leslie was for many years so much above his necessities, that he was able,
by careful management, to realise a fortune not far short of ten thousand
pounds. Part of this he expended, in his latter years, upon the purchase and
decoration of a mansion called Coates near his native village, where he
spent all the intervals allowed by his college duties. Early in the year
1832, at the recommendation of the lord chancellor (Brougham), he was
invested with a knighthood of the Guelphic order, at the same time that
Messrs Herschel, C. Bell, Ivory, Brewster, South, and Harris Nicolas,
received a similar honour. Sir John Leslie was not destined long to enjoy
the well-merited honour. In the end of October, while superintending some of
the improvements about his much-loved place, he incautiously exposed himself
to wet, the consequence of which was a severe cold. Among the various
foibles which protruded themselves through the better powers and habitudes
of his mind, was a contempt for medicine, and an unwillingness to think that
he could be seriously ill. He accordingly neglected his ailment, and was
speedily seized with erysipelas in one of his legs; a disorder at that time
raging in Scotland with all the symptoms and effects of a malignant
epidemic. On Wednesday, October 31st, he again exposed himself in his
grounds, and from that day, the malady advanced very rapidly. On the evening
of Saturday, November 3d, he breathed his last.
The scientific and personal
character of Sir John Leslie has been sketched with so bold and free a
pencil by Mr Macvey Napier, his brother in both academic and literary
labours, that we make no apology for presenting it to the reader, in lieu of
any thing of our own:
"It would be impossible, we
think, for any intelligent and well-constituted mind, to review the labours
of this distinguished man, without a strong feeling of admiration for his
inventive genius and vigorous powers, and of respect for that extensive
knowledge which his active curiosity, his various reading, and his happy
memory had enabled him to attain. Some few of his contemporaries in the same
walks of science, may have excelled him in profundity of understanding, in
philosophical caution, and in logical accuracy; but we doubt if any
surpassed him, whilst he must be allowed to have surpassed many, in that
creative faculty—one of the highest and rarest of nature’s gifts—which
leads, and is necessary to discovery, though not all-sufficient of itself
for the formation of safe conclusions; or in that subtilty and reach of
discernment which seizes the finest and least obvious relations among the
objects of science—which elicits the hidden secrets of nature, and ministers
to new combinations of her powers. There were some flaws, it must be
allowed, in the mind of this memorable person. He strangely undervalued some
branches of philosophical inquiry of high importance in the circle of human
knowledge. His credulity in matters of ordinary life was, to say the least
of it, as conspicuous as his tendency to scepticism in science. It has been
profoundly remarked by Mr Dugald Stewart, that ‘though the mathematician may
be prevented, in his own pursuits, from going far astray, by the absurdities
to which his errors lead him, he is seldom apt to be revolted by absurd
conclusions in other matters. Thus, even in physics,’ he adds,
‘mathematicians have been led to acquiesce in conclusions which appear
ludicrous to men of different habits.’ Something of the same kind was
observable in the mind of this distinguished mathematician, for such also he
was. He was apt, too, to run into some startling hypothesis, from an
unwarrantable application of mathematical principles to subjects altogether
foreign to them; as when he finds an analogy between circulating decimals,
and the lengthened cycles of the seasons. In all his writings, with the
exception, perhaps, of his last considerable performance, the discourse
prefixed to the seventh edition of the Encyclopaedia Britannica, even in the
sober field of pure mathematics, there is a constant straining after
‘thoughts that breathe and words that burn,’ and a love of abstract, and
figurative, and novel modes of expression, which has exposed them to just
criticism, by impartial judges, and to some puny fault-finding, by others,
more willing to carp at defects than to point out the merits which redeem
them. But when even severe criticism has said its worst, it must be allowed,
that genius has struck its captivating impress, deep and wide over all his
works. His more airy speculations may be thrown aside or condemned; but his
exquisite instruments, and his original and beautiful experimental
combinations, will ever attest the fruitfulness of his mind, and continue to
act as helps to farther discovery. We have already alluded to the extent and
excursiveness of his reading. It is rare, indeed, to find a man of so much
invention, and who himself valued the inventive above all the other powers,
possessing so vast a store of learned and curious information. His reading
extended to every nook and corner, however obscure, that books have touched
upon. He was a lover, too, and that in no ordinary degree, of what is
commonly called anecdote. Though he did not shine in mixed society, and was
latterly unfitted by a considerable degree of deafness for enjoying it, his
conversation, when seated with one or two, was highly entertaining. It had
no wit, little repartee, and no fine turns of any kind, but it had a
strongly original and racy cast, and was replete with striking remarks and
curious information.
"He had faults, no doubt, as
all ‘of woman born’ have: he had prejudices, of which it would have been
better to be rid; he was not over charitable in his views of human virtue;
and he was not quite so ready, on all occasions, to do that justice to
kindred merit as was to be expected in so ardent a worshipper of genius. But
his faults were far more than compensated by his many good qualities—by his
constant equanimity, his cheerfulness, his simplicity of character, almost
infantine, his straightforwardness, his perfect freedom from affectation,
and, above all, his unconquerable good nature. [The person of Sir John
Leslie was, in later life, far from gainly. It was short and corpulent with
a florid face, and somewhat unsightly projection of the front teeth, and
tottered considerably in walking. He was, moreover, very slovenly in his
mode of dressing—a peculiarity the more curious, as it was accompanied by no
inconsiderable share of self-respect and an anxiety to be thought
young and engaging. The mixture of great intellectual powers with the
humbler weaknesses of human nature, can seldom have been more strikingly
exemplified than in his case; though it is evident that, as his weaknesses
were very much those to which unmarried men in advanced life are supposed to
be most peculiarly liable, they might have probably been obviated in a great
measure, if he had happened to spend his life in the more fortunate
condition of matrimony.] He was, indeed, one of the most placable of human
beings; and if, as has been thought, he generally had a steady eye, in his
worldly course, to his own interest, it cannot be denied that he was,
notwithstanding, a warm and good friend, and a relation on whose
affectionate assistance a firm reliance could ever be placed.
"There is one other matter
which, in justice to the illustrious dead, we cannot pass over in silence;
we mean the permanent service rendered to the class of Natural Philosophy by
the late Sir John Leslie in the collection of by far the finest and most
complete set of apparatus in the kingdom. Augustus boasted that he found
Rome built of brick, and left it a city of palaces and temples constructed
of marble. Without any exaggeration, something analogous may be predicated
of Sir John Leslie in regard to the apparatus of this class. He found it a
collection of antiquated and obsolete rubbish; he left it the most complete
and perfect of its kind in this kingdom; and if it had pleased God to spare
him a few years longer, it would, beyond all doubt, have been rendered the
first in Europe or the world. The renovation which he effected was, indeed,
most radically complete. The whole of the old trash was thrown aside, and
its place supplied by new instruments, constructed on the most improved
principles by the most celebrated artists, both in this country and on the
continent; while its absolute amount was increased tenfold, and adapted, in
the happiest manner, to the present advanced state of science. His
perseverance and enthusiasm in this respect were indeed boundless; and as
his predecessors were not experimentalists, in the same sense in which he
was, and had made little or no effort to accommodate the apparatus to the
progress of science, or even to repair the wear and tear of time, he had the
whole to create, in the same way as if the class had only been founded when
he was first promoted to the chair. By his own continued and
admirably-directed efforts, aided by the liberality of the patrons, who
generously made him several grants in furtherance of the object which he had
so much at heart; and also by very considerable pecuniary sacrifices upon
his own part, for which he has never as yet got the credit that is so justly
due to him; he at length succeeded in furnishing the apparatus-room in the
manner in which it may now be seen by any one who chooses to visit it, and
thus conferred upon the university a benefit for which it ought to be for
ever grateful to his memory. This may sound strange in the ears of those who
have been accustomed to hear it said, as it has often been, most falsely,
that Sir John Leslie was a bad experimenter. The truth is, that of all his
great and varied gifts, none was more remarkable than the delicacy and
success with which he performed the most difficult experiments, excepting
perhaps his intuitive sagacity in instantly detecting the cause of an
accidental failure; and it is a known fact, that, after he had discovered
and communicated to the world his celebrated process of artificial
congelation, particularly as applied to the freezing of mercury, some of the
first men of science in London failed of performing it, till the discoverer
himself, happening to be on the spot personally, showed them wherein
consisted the fault of their manipulation, and at once performed the
experiment which had previously baffled all their efforts. It is equally
well known to those who were acquainted with him, that the most elegant in
form as well as the most delicate in operation of the beautiful instruments
invented by himself, were constructed by his own hand, and that this, to him
most agreeable employment, constituted the recreation of his leisure hours.
The apparatus-room, indeed, contains many specimens of his workmanship in
this line, and they are of such a description as would not do any discredit
to the most practised and skilful artist. To his immediate successor his
acquisitions and his labours will, therefore, be of incalculable importance;
but the merit which really belongs to him can only be duly estimated by
those who know what he found, when he became professor of natural
philosophy, and can compare it with the treasures which he has left behind
him."
[Some further particulars
respecting his various talents and acquirements may be gathered from the
following notice, which appeared in the Edinburgh Courant, and seems to be
the production of one qualified in more ways than one to speak upon the
subject:—"Sir John Leslie has been for many years known in this country, and
over all Europe, as one of the most eminent characters of the age. As a
mathematician and philosopher; as a profound and accomplished scholar; as a
proficient in general literature, and in history and many other branches of
knowledge, he had few rivals. But it was for mathematical science and its
kindred studies, that he discovered, at a very early period, a decided
predilection; and it is in the successful illustration of scientific truth
and of all the complicated phenomena of physics, that his great reputation
has been acquired. In these pursuits he was eminently qualified to excel by
the great original powers of his mind, which were further stimulated by an
ardent enthusiasm, and an early desire of distinction among the illustrious
names of his day. Along with a profound knowledge of his subject, he
possessed great inventive powers, which not only enabled him to sound the
depths of science, but to expound its important problems with a simplicity
and elegance rarely equaled. In making his way through the intricacies of
physical research, his severe judgment guided him in the right path; and
hence his demonstrations always afford a striking and beautiful display of
pure reason, without any tendency to that spirit of metaphysical subtlety
which occasionally perplexes the speculations of Laplace, Legendre, with
others of the continental philosophers; and it is worthy of remark that,
along with the penetrating force of his judgment, he carried into those
studies that taste and fancy—that predilection for the beautiful, which may
be recognised in all his speculations, whether in literature or in science.
His taste in geometry was founded on the purest models of Grecian
philosophy; he delighted to expound to his pupils the simplicity and
elegance of the demonstrations by the great masters of antiquity; he
commended them to their imitation, and expatiated on the subject in a manner
well fitted to inspire a kindred enthusiasm; so that we might have fancied
that he was dilating, not on the merits of a mathematical problem, but on
some of those beautiful forms and classic models of ancient art which have
been the wonder of all succeeding times. Nor was this admiration of ancient
geometry a mere pedantic or barren speculation. The great philosopher of
whom we are speaking carried his principles into practice, and applied the
abstract properties of figures with the happiest success to experimental
philosophs; many branches of which he greatly extended by his discoveries;
and in all of them he developed the most original views, which may yet be
traced to important results. The range of his studies was amazingly
extensive; and he had accumulated vast stores of knowledge, especially on
scientific subjects. He was deeply versed in the history of science, which
he had traced from its earliest dawnings in the times of Greece and Rome,
through all the subsequent vicissitudes which it experienced during the dark
ages of barbarism, till it was revived by the Arabians in the east,
and was afterwards improved and perfected by the more brilliant discoveries
of modern times. We speak literally when we say, that we doubt if there is a
single publication relating to this subject, either in the ancient or the
modern languages, which he had not diligently perused; and his knowledge,
minute and accurate on every point, and, once acquired, never forgotten,
overflowed in his conversation and in his writings. The date of any great
discovery was familiar to him; he could give anecdotes or biographical
sketches of all the great promoters of science in every age; and the
prodigality of his information was not more surprising than the ease with
which he preserved its disposition and arrangement, under certain great
leading principles, which were the land-marks of his mind, by which the
store of facts which he had been treasuring up for years was reduced into
order, and each distributed into its proper place in the great system of
which it formed a part. For the truth of this remark we may refer to the
‘History of the Barometer,’ in the Edinburgh Review, and to his papers on
Meteorology, and other subjects in the Encyclopaedia Britannica, to his
continuation of Playfair’s Introductory Discourses prefixed to that work, as
well as to many of his other productions, which display the great extent of
his researches. On other subjects, also, not connected with his peculiar
studies, his information was minute and extensive. He was deeply read in
Scottish history and antiquities; and on all modern questions of
politics or political economy, he had his own original ideas, which he was
always ready to express and expound in a fair and temperate strain."]