OF THE FOUNDATION AND PROGRESS OF SCIENTIFIC CHEMISTRY IN GREAT BRITAIN.
The spirit which Newton had infused for the mathematical science
was so great, that during many years they drew within their vortex
almost all the scientific men in Great Britain. Dr. Stephen Hales is
almost the only remarkable exception, during the early part of the
eighteenth century. His vegetable statics constituted a most ingenious
and valuable contribution to vegetable physiology. His hæmastatics was
a no less valuable contribution to iatro-mathematics, at that time
the fashionable medical theory in Great Britain. While his _analysis
of air_, and experiments on the animal calculus constituted, in all
probability, the foundation-stone of the whole discoveries respecting
the gases to which the great subsequent progress of chemistry is
chiefly owing.
Dr. William Cullen, to whom medicine lies under deep obligations,
and who afterwards raised the medical celebrity of the College of
Edinburgh to so high a pitch, had the merit of first perceiving the
importance of scientific chemistry, and the reputation which that man
was likely to earn, who should devote himself to the cultivation of
it. Hitherto chemistry in Great Britain, and on the continent also,
was considered as a mere appendage to medicine, and useful only so
far as it contributed to the formation of new and useful remedies.
This was the reason why it came to constitute an essential part of the
education of every medical man, and why a physician was considered as
unfit for practice unless he was also a chemist. But Dr. Cullen viewed
the science as far more important; as capable of throwing light on the
constitution of bodies, and of improving and amending of those arts and
manufactures that are most useful to man. He resolved to devote himself
to its cultivation and improvement; and he would undoubtedly have
derived celebrity from this science, had not his fate led rather to the
cultivation of medicine. But Dr. Cullen, as the true commencer of the
study of scientific chemistry in Great Britain, claims a conspicuous
place in this historical sketch.
William Cullen was born in Lanarkshire, in Scotland, in the year
1712, on the 11th of December. His father, though chief magistrate of
Hamilton, was not in circumstances to lay out much money on his son.
William, therefore, after serving an apprenticeship to a surgeon in
Glasgow, went several voyages to the West Indies, as surgeon, in a
trading-vessel from London; but tiring of this, he settled, when very
young, in the parish of Shotts; and after residing for a short time
among the farmers and country people, he went to Hamilton, with a view
of practising as a physician.
While he resided near Shotts, it happened that Archibald, Duke of
Argyle, who at that time bore the chief political sway in Scotland,
paid a visit to a gentleman of rank in that neighbourhood. The duke
was fond of science, and was at that time engaged in some chemical
researches which required to be elucidated by experiment. Eager in
these pursuits, while on his visit he found himself at a loss for some
piece of chemical apparatus which his landlord could not furnish; but
he mentioned young Cullen to the duke as a person fond of chemistry,
and likely therefore to possess the required apparatus. He was
accordingly invited to dine, and introduced to his Grace. The duke
was so pleased with his knowledge, politeness, and address, that an
acquaintance commenced, which laid the foundation of all Cullen’s
future advancement.
His residence in Hamilton naturally made his name known to the Duke of
Hamilton, whose palace is situated in the immediate vicinity of that
town. His Grace being taken with a sudden illness, sent for Cullen,
and was highly delighted with the sprightly character, and ingenious
conversation of the young physician. He found no difficulty, especially
as young Cullen was already known to the Duke of Argyle, in getting him
appointed to a place in the University of Glasgow, where his singular
talents as a teacher soon became very conspicuous.
It was while Dr. Cullen was a practitioner in Shotts that he formed a
connexion with William, afterwards Doctor Hunter, the famous lecturer
on anatomy in London, who was a native of the same part of the country
as Cullen. These two young men, stimulated by genius, though thwarted
by the narrowness of their circumstances, entered into a copartnery
business, as surgeons and apothecaries, in the country. The chief
object of their contract was to furnish the parties with the means
of carrying on their medical studies, which they were not able to do
separately. It was stipulated that one of them, alternately, should be
allowed to study in whatever college he preferred, during the winter,
while the other carried on the common business in his absence. In
consequence of this agreement, Cullen was first allowed to study in
the University of Edinburgh, for a winter. When it came to Hunter’s
turn next winter, he rather chose to go to London. There his singular
neatness in dissecting, and uncommon dexterity in making anatomical
preparations, his assiduity in study, his mild manners, and easy
temper, drew upon him the attention of Dr. Douglas, who at that time
read lectures on anatomy and midwifery in the capital. He engaged
him as his assistant, and he afterwards succeeded him in the same
department with much honour to himself, and advantage to the public.
Thus was dissolved a copartnership of perhaps as singular a kind as any
that occurs in the annals of science. Cullen was not disposed to let
any engagement with him prove a bar to his partner’s advancement in the
world. The articles were abandoned, and Cullen and Hunter kept up ever
after a friendly correspondence; though there is reason to believe that
they never afterwards met.
It was while a country practitioner that young Cullen married a Miss
Johnston, daughter of a neighbouring clergyman. The connexion was
fortunate and lasting. She brought her husband a numerous family, and
continued his faithful companion through all the alterations of his
fortune. She died in the summer of 1786.
In the year 1746 Cullen, who had now taken the degree of doctor of
medicine, was appointed lecturer on chemistry in the University of
Glasgow; and in the month of October began a course on that science.
His singular talent for arrangement, his distinctness of enunciation,
his vivacity of manner, and his knowledge of the science which he
taught, rendered his lectures interesting to a degree which had
been till then unknown in that university: he was adored by the
students. The former professors were eclipsed by the brilliancy of his
reputation, and he had to encounter all those little rubs and insults
that disappointed envy naturally threw in his way. But he proceeded in
his career regardless of these petty mortifications; and supported by
the public, he was more than consoled for the contumely heaped upon him
by the ill nature and pitiful malignity of his colleagues. His practice
as a physician increased every day, and a vacancy occurring in the
chair in 1751, he was appointed by the crown professor of medicine,
which put him on a footing of equality with his colleagues in the
university. This new appointment called forth powers which he was not
before known to possess, and thus served still further to increase his
reputation.
At that time the patrons of the University of Edinburgh were eagerly
bent on raising the reputation of their medical school, and were in
consequence on the look out for men of abilities and reputation to fill
their respective chairs. Their attention was soon drawn towards Cullen,
and on the death of Dr. Plummer, in 1756, he was unanimously invited to
fill the vacant _chemical chair_. He accepted the invitation, and began
his academical career in the College of Edinburgh in October of that
year, and here he continued during the remainder of his life.
The appearance of Dr. Cullen in the College of Edinburgh constitutes
a memorable era in the progress of that celebrated school. Hitherto
chemistry being reckoned of little importance, had been attended by
very few students; when Cullen began to lecture it became a favourite
study, almost all the students flocking to hear him, and the chemical
class becoming immediately more numerous than any other in the college,
anatomy alone excepted. The students in general spoke of the new
professor with that rapturous ardour so natural to young men when
highly pleased. These eulogiums were doubtless extravagant, and proved
disgusting to his colleagues. A party was formed to oppose this new
favourite of the public. His opinions were misrepresented, it was
affirmed that he taught doctrines which excited the alarm of some of
the most moderate and conscientious of his colleagues. Thus a violent
ferment was excited, and some time elapsed before the malignant arts by
which this flame had been blown up were discovered.
During this time of public ferment Cullen went steadily forward; he
never gave an ear to the gossip brought him respecting the conduct
of his colleagues, nor did he take any notice of the doctrines which
they taught. Some of their unguarded strictures on himself might
occasionally have come to his ears; but if it was so, he took no notice
of them whatever; they seemed to have made no impression on him.
This futile attempt to lower his character being thus baffled, his fame
as a professor, and his reputation as a physician, increased daily: nor
could it be otherwise; his professional knowledge was always great, and
his manner of lecturing singularly clear and intelligible, lively, and
entertaining. To his patients his conduct was so pleasing, his address
so affable and engaging, and his manner so open, so kind, and so little
regulated by pecuniary considerations, that those who once applied to
him for medical assistance could never afterwards dispense with it: he
became the friend and companion of every family he visited, and his
future acquaintance could not be dispensed with.
His private conduct to his students was admirable, and deservedly
endeared him to every one of them. He was so uniformly attentive to
them, and took so much interest in the concerns of those who applied
to him for advice; was so cordial and so warm, that it was impossible
for any one, who had a heart susceptible of generous emotions, not to
be delighted with a conduct so uncommon and so kind. It was this which
served more than any thing else to extend his reputation over every
civilized quarter of the globe. Among ingenuous youth gratitude easily
degenerates into rapture; hence the popularity which he enjoyed, and
which to those who do not well weigh the causes which operated on the
students must appear excessive.
The general conduct of Cullen to his students was this: with all
such as he observed to be attentive and diligent he formed an early
acquaintance, by inviting them by twos, by threes, and by fours at a
time to sup with him; conversing with them at such times with the most
engaging ease, entering freely with them into the subject of their
studies, their amusements, their difficulties, their hopes and future
prospects. In this way he usually invited the whole of his numerous
class till he made himself acquainted with their private character,
their abilities, and their objects of pursuit. Those of whom he formed
the highest opinion were of course invited most frequently, till an
intimacy was gradually formed which proved highly beneficial to them.
To their doubts and difficulties he listened with the most obliging
condescension, and he solved them to the utmost of his power. His
library was at all times open for their accommodation: in short, he
treated them as if they had been all his relatives and friends. Few men
of distinction left the University of Edinburgh, in his time, with whom
he did not keep up a correspondence till they were fairly established
in business. This enabled him gradually to form an accurate knowledge
of the state of medicine in every country, and the knowledge thus
acquired put it in his power to direct students in the choice of places
where they might have an opportunity of engaging in business with a
reasonable prospect of success.
Nor was it in this way alone that he befriended the students in the
University of Edinburgh. Remembering the difficulties with which he had
himself to struggle in his younger days, he was at all times singularly
attentive to the pecuniary wants of the students. From the general
intimacy which he contracted with them he found no difficulty in
discovering those whose circumstances were contracted, or who laboured
under any pecuniary embarrassment, without being under the necessity of
hurting their feelings by a direct inquiry. To such persons, when their
habits of study admitted it, he was peculiarly attentive: they were
more frequently invited to his house than others, they were treated
with unusual kindness and familiarity, they were conducted to his
library and encouraged by the most delicate address to borrow from it
freely whatever books he thought they had occasion for; and as persons
under such circumstances are often extremely shy, books were sometimes
pressed upon them as a sort of task, the doctor insisting upon knowing
their opinion of such and such passages which they had not read, and
desiring them to carry the book home for that purpose: in short, he
behaved to them as if he had courted their company. He thus raised
them in the opinion of their acquaintances, which, to persons in their
circumstances, was of no little consequence. They were inspired at the
same time with a secret sense of dignity, which elevated their minds,
and excited an uncommon ardour, instead of that desponding inactivity
so natural to depressed circumstances. Nor was he less delicate in the
manner of supplying their wants: he often found out some polite excuse
for refusing to take money for a first course, and never was at a loss
for one to an after course. Sometimes (as his lectures were never
written) he would request the favour of a sight of their notes, if he
knew that they were taken with care, in order to refresh his memory.
Sometimes he would express a wish to have their opinion of a particular
part of his course, and presented them with a ticket for the purpose.
By such delicate pieces of address, in which he greatly excelled, he
took care to anticipate their wants. Thus he not only gave them the
benefit of his own lectures, but by refusing to take money enabled them
to attend such others as were necessary for completing their course of
medical study.
He introduced another general rule into the university dictated by the
same spirit of disinterested benevolence. Before he came to Edinburgh,
it was the custom of the medical professors to accept of fees for their
medical attendance when wanted, even from medical students themselves,
though they were perhaps attending the professor’s lectures at the
time. But Dr. Cullen never would take a fee from any student of the
university, though he attended them, when called on as a physician,
with the same assiduity and care as if they had been persons of the
first rank who paid him most liberally. This gradually led others
to follow his example; and it has now become a general rule for
medical professors to decline taking any fees when their assistance
is necessary to a student. For this useful reform, as well as for
many others, the students in the University of Edinburgh are entirely
indebted to Dr. Cullen.
The first lectures which Dr. Cullen delivered in Edinburgh were on
chemistry; and for many years he also gave lectures on the cases
that occurred in the infirmary. In the month of February, 1763, Dr.
Alston died, after having begun his usual course of lectures on the
materia medica. The magistrates of Edinburgh, who are the patrons of
the university, appointed Dr. Cullen to that chair, requesting that
he would finish the course of lectures that had been begun by his
predecessor. This he agreed to do, and, though he had only a few days
to prepare himself, he never once thought of reading the lectures of
his predecessor, but resolved to deliver a new course, which should be
entirely his own. Some idea may be formed of the popularity of Cullen,
by the increase of students to a class nearly half finished: Dr. Alston
had been lecturing to ten; as soon as Dr. Cullen began, a hundred new
students enrolled themselves.
Some years after, on the death of Dr. Whytt, professor of the theory of
medicine, Dr. Cullen was appointed to give lectures in his stead. It
was then that he thought it requisite to resign the chemical chair in
favour of Dr. Black, his former pupil, whose talents in that department
of science were well known. Soon after, on the death of Dr. Rutherford,
professor of the practice of medicine, Dr. John Gregory having become a
candidate for this place, along with Dr. Cullen, a sort of compromise
took place between them, by which they agreed to give lectures
alternately, on the theory and practice of medicine, during their joint
lives, the longest survivor being allowed to hold either of the classes
he should incline. Unluckily this arrangement was soon destroyed, by
the sudden and unexpected death of Dr. Gregory, in the flower of his
age. Dr. Cullen thenceforth continued to give lectures on the practice
of medicine till within a few months of his death, which happened on
the 5th of February, 1790, when he was in the seventy-seventh year of
his age.
It is not our business to follow Dr. Cullen’s medical career, nor
to point out the great benefits which he conferred on nosology and
the practice of medicine. He taught four different classes in the
University of Edinburgh, which we are not aware to have happened to any
other individual, except to professor Dugald Stewart.
Notwithstanding the important impulse which he gave to chemistry,
he published nothing upon that science, except a short paper on the
cold produced by the evaporation of ether, which made its appearance
in one of the volumes of the Edinburgh Physical and Literary Essays.
Dr. Cullen employed Dr. Dobson of Liverpool, at that time his pupil,
to make experiments on the heat and cold produced by mixing liquids
and solids with each other. Dr. Dobson, in making these experiments,
observed that the thermometer, when lifted out of many of the liquids,
and suspended a short time in the air beside them, fell to a lower
degree than indicated by another thermometer which had undergone no
such process. After varying his observations on this phenomenon, he
found reason to conclude that it was occasioned by the evaporation of
the last drop of liquid which adhered to the bulb of the thermometer;
the sinking of the thermometer being always greatest when this
instrument was taken out of the most volatile liquids. Dr. Cullen
had the curiosity to try whether the same phenomenon would appear
on repeating these experiments under the exhausted receiver of an
air-pump. To satisfy himself, he put on the plate of the air-pump
a glass goblet containing water; and in the goblet he placed a
wide-mouthed phial containing sulphuric ether. The whole was covered
with an air-pump receiver, having at the upper end a collar of leathers
in a brass socket, through which a thick smooth wire could be moved;
and from the lower end of this wire, projecting into the receiver, was
suspended a thermometer. By pushing down the wire, the thermometer
could be dipped into the ether; by drawing it up it could be taken out,
and suspended over the phial.
The apparatus being thus adjusted, the air-pump was worked to extract
the air. An unexpected phenomenon immediately appeared, which prevented
the experiment from being made in the way intended. The ether was
thrown into a violent agitation, which Dr. Cullen ascribed to the
extrication of a great quantity of air: in reality, however, it was
boiling violently. What was still more remarkable, the ether, by this
boiling or rapid evaporation, became all of a sudden so cold, as to
freeze the water in the goblet around it; though the temperature of
the air and of all the materials were at the fifty-fourth degree of
Fahrenheit at the beginning of the experiment.
I have been particular in giving an account of this curious phenomenon,
as it was the only direct contribution to the science of chemistry
which Dr. Cullen communicated to the public. The nature of the
phenomenon was afterwards explained by Dr. Black; in addition to Dr.
Cullen, a philosopher, whom the grand stimulus which his lectures gave
to the cultivation of scientific chemistry in this country, had the
important merit of bringing forward.
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, but
of a Scottish family which had been for some time settled there. Mr.
Black resided for the most part at Bordeaux, where he was engaged in
the wine trade. He married a daughter of Mr. Robert Gordon, of the
family of Hillhead, in Aberdeenshire, who was also engaged in the same
trade at Bordeaux. Mr. Black was a gentleman of most amiable manners,
candid and liberal in his sentiments, and of no common information.
These qualities, together with the warmth of his heart, appear very
conspicuous in a series of letters to his son, which that son preserved
with the nicest care. His good qualities did not escape the discerning
eye of the great Montesquieu, one of the presidents of the court of
justice in that province. This illustrious and excellent man honoured
Mr. Black with a friendship and intimacy altogether rare; of which his
descendants were justly proud.
Long before Mr. Black retired from business, his son Joseph was sent
home to Belfast, that he might have the education of a British subject.
This was in the year 1740, when he was twelve years of age. After the
ordinary instruction at the grammar-school, he was sent, in 1746, to
continue his education in the University of Glasgow. Here he studied
with much assiduity and success: physical science, however, chiefly
engrossed his attention. He was a favourite pupil of Dr. Robert Dick,
professor of natural philosophy, and the intimate companion of his
son and successor. This young professor was of a character peculiarly
suited to Dr. Black’s taste, having the clearest conception, and
soundest judgment, accompanied by a modesty that was very uncommon.
When he succeeded his father, in 1751, he became the delight of the
students. He was carried off by a fever in 1757.
Young Black being required by his father to make choice of a
profession, he preferred that of medicine as the most suitable to the
general habits of his studies. Fortunately Dr. Cullen had just begun
his great career in the College of Glasgow, and having made choice
of the field of philosophical chemistry which lay as yet unoccupied
before him. Hitherto chemistry had been treated as a curious and useful
art; but Cullen saw in it a vast department of the science of nature,
depending on principles as immutable as the laws of mechanism, and
capable of being formed into a system as comprehensive and as complete
as astronomy itself. He conceived the resolution of attempting himself
to explore this magnificent field, and expected much reputation from
accomplishing his object. Nor was he altogether disappointed. He
quickly took the science out of the hands of artists, and exhibited
it as a study fit for a gentleman. Dr. Black attended his chemical
lectures, and, from the character which has already been given of him,
it is needless to say that he soon discovered the uncommon value of
his pupil, and attached him to himself, rather as a co-operator and a
friend, than a pupil. He was considered as his assistant in all his
operations, and his experiments were frequently adduced in the lecture
as good authority.
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.
It was during his residence in Glasgow, between the years 1759 and
1763, that he brought to maturity those speculations concerning the
combination of _heat_ with _matter_, which had frequently occupied
a portion of his thoughts. It had long been known that ice has the
property of continuing always at the temperature of 32° till it be
melted. This happens equally though it be placed in contact with the
warm hand or surrounded with bodies many degrees hotter than itself.
The hotter the bodies are that surround it, the sooner is it melted;
but its temperature during the whole process of melting, continues
uniformly the same. Yet, during the whole process of melting, it is
constantly robbing the surrounding bodies of heat; for it makes them
colder, without acquiring itself any sensible heat.
Dr. Black had some vague notion that the heat so received by the ice,
during its conversion into water, was not lost, but was contained in
the water. This opinion was founded chiefly on a curious observation
of Fahrenheit, recorded by Boerhaave; namely, that water might in some
cases be made considerably colder than melting snow, without freezing.
In such cases, when disturbed it would freeze in a moment, and in the
act of freezing always gave out a quantity of heat. This opinion was
confirmed by observing the slowness with which water is converted
into ice, and ice into water. A fine winter-day of sunshine is never
sufficient to clear the hills of snow; nor is one frosty night capable
of covering the ponds with a thick coating of ice. The phenomena
satisfied him that much heat was absorbed and fixed in the water which
trickles from wreaths of snow, and that much heat emerged from it while
water was slowly converted into ice; for during a thaw the melting snow
is always colder than the air, and must, therefore, be always receiving
heat from it; while, during a frost, the air is always colder than the
freezing water, and must therefore be always receiving heat from it.
These observations, and many others which it is needless to state,
satisfied Dr. Black that when ice is converted into water it unites
with a quantity of heat, without increasing in temperature; and that
when water is frozen into ice it gives out a quantity of heat without
diminishing in temperature. The heat thus combined is the cause of the
fluidity of the water. As it is not sensible to the thermometer, Dr.
Black called it _latent heat_. He made an experiment to determine the
quantity of heat necessary to convert ice into water. This he estimated
by the length of time necessary to melt a given weight of ice,
measuring how much heat entered into the same weight of water, reduced
as nearly to the temperature of ice as possible during the first
half-hour that the experiment lasted. As the ice continued during the
whole of its melting at the same temperature as at first, he concluded
that it would absorb, every half-hour that the process lasted, as much
heat as the water did during the first half hour. The result of this
experiment was, that the latent heat of water amounts to 140°; or, in
other words, that this heat, if thrown into a quantity of water, equal
in weight to that of the ice melted, would raise its temperature 140°.
Dr. Black, having established this discovery in the most
incontrovertible manner by simple and decisive experiments, drew up an
account of the whole investigation, and the doctrine which he founded
upon it, and read it to a literary society which met every Friday in
the faculty-room of the college, consisting of the members of the
university and several gentlemen of the city, who had a relish for
science and literature. This paper was read on the 23d of April, as
appears by the registers of the society.
Dr. Black quickly perceived the vast importance of this discovery, and
took a pleasure in laying before his students a view of the beneficial
effects of this habitude of heat in the economy of nature. During the
summer season a vast magazine of heat was accumulated in the water,
which, by gradually emerging during congelation, serves to temper the
cold of winter. Were it not for this accumulation of heat in water and
other bodies, the sun would no sooner go a few degrees to the south of
the equator, than we should feel all the horrors of winter. He did not
confine his views to the congelation of water alone, but extended them
to every case of congelation and liquefaction which he has ascribed
equally to the evolution or fixation of latent heat. Even those bodies
which change from solid to fluid, not all at once, but by slow degrees,
as butter, tallow, resins, owe, he found, their gradual softening to
the same absorption of heat, and the same combination of it with the
substance undergoing liquefaction.
Another subject that engaged his attention at this time, was an
examination of the scale of the thermometer, to learn whether
equal differences of expansion corresponded to equal additions or
abstractions of heat. His mode was to mix together equal weights of
water of different temperatures, and to measure the temperature of the
mixture by a thermometer. It is obvious that the temperature must be
the exact mean of that of the two portions of water; and that if the
expansion or contraction of the mercury in the thermometer be an exact
measure of the difference of temperature, a thermometer, so placed,
will indicate the exact mean. Suppose one pound of water at 100° to
be mixed with one pound of water at 200°, and the whole heat still
to remain in the mixture, it is obvious that it would divide itself
equally between the two portions of water. The water of 100° would
become hotter, and the water of 200° would become colder: and the
increase of temperature in the colder portion would be just as much
as the diminution of temperature in the hotter portion. The colder
portion would become hotter by 50°, while the hotter portion would
become colder by 50°. Hence the real temperature, after mixture, would
be 150°; and a thermometer plunged into such a mixture, if a true
measurer of heat, would indicate 150°. The result of his experiments
was, that as high up as he could try by mixing water of different
temperatures, the mercurial thermometer is an accurate measurer of the
alterations of temperature.
An account of his experiments on this subject was drawn up by him, and
read to the literary society of the College of Glasgow, on the 28th of
March, 1760. Dr. Black, at the time he made these experiments, did not
know that he had been already anticipated in them by Dr. Brooke Taylor,
the celebrated mathematician, who had obtained similar results, and had
consigned his experiments to the Royal Society, in whose Transactions
for 1723 they were published. It has been since found by Coulomb
and Petit, that at higher temperatures than 212° the rate of the
expansion of mercury begins to increase. Hence it happens that at high
temperatures the expansion of mercury is no longer an accurate measurer
of temperature. Fortunately, the expansion of glass very nearly equals
the increment of that of mercury. The consequence is, that in a common
glass-thermometer mercury measures the true increments of temperature
very nearly up to its boiling point; for the boiling point of mercury
measured by an air-thermometer is 662°: and if a glass mercurial
thermometer be plunged into boiling mercury, it will indicate 660°, a
difference of only 2° from the true point.
There is such an analogy between the cessation of thermometric
expansion during the liquefaction of ice, and during the conversion of
water into steam, that there could be no hesitation about explaining
both in the same way. Dr. Black immediately concluded that as water is
ice united to a certain quantity of _latent heat_, so steam is water
united to a still greater quantity. The slow conversion of water into
steam, notwithstanding the great quantity of heat constantly flowing
into it from the fire, left no reasonable doubt about the accuracy of
this conclusion. In short, all the phenomena are precisely similar to
those of the conversion of ice into water; and so, of course, must
the explanation be. So much was he convinced of this, that he taught
the doctrine in his lectures in 1761, before he had made a single
experiment on the subject; and he explained, with great felicity of
argument, many phenomena of nature, which result from this vaporific
combination of heat. From notes taken in his class during this session,
it appears that nothing more was wanting to complete his views on this
subject, than a set of experiments to determine the exact quantity
of heat which was combined in steam in a state not indicated by the
thermometer, and therefore _latent_, in the same sense that the heat of
liquefaction in water is _latent_.
The requisite experiments were first attempted by Dr. Black, in 1764.
They consisted merely in measuring the time requisite to convert a
certain weight of water of a given temperature into steam. The water
was put into a tin-plate wide-mouthed vessel, and laid upon a red-hot
plate of iron, the initial temperature of the water was marked, and the
time necessary to heat it from that point to the boiling point noted,
and then the time requisite to boil the whole to dryness. It was taken
for granted that as much heat would enter into the water during every
minute that the experiment lasted, as did during the first minute. From
this it was concluded that the latent heat of steam is not less than
810 degrees.
Mr. James Watt afterwards repeated these experiments with a better
apparatus and very great care, and calculated from his results that the
latent heat of steam is not under 950 degrees. Lavoisier and Laplace
afterwards made experiments in a different way, and deduced 1000° as
the result of their experiments. The subsequent experiments of Count
Rumford, made in a very ingenious manner, so as to obviate most of the
sources of error, to which such researches are liable, come very nearly
to those of Lavoisier. 1000° therefore, is usually now-a-days adopted
as the number which denotes the true latent heat of steam.
Dr. Black continued in the University of Glasgow from 1756 to 1766,
much esteemed as an eminent professor, much employed as an able and
attentive physician, and much beloved as an amiable and accomplished
man, happy in the enjoyment of a small but select society of friends.
Meanwhile his reputation as a chemical philosopher was every day
increasing, and pupils from foreign countries carried home with them
the peculiar doctrines of his courses--so that _fixed air_ and _latent
heat_ began to be spoken of among the naturalists of the continent. In
1766 Dr. Cullen, at that time professor of chemistry 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 regard
to a successor. Indeed, when the vacancy happened in 1756, on the death
of Dr. Plummer, the reputation of Dr. Black, who had just taken his
degree, was so high, both as a chemist and an accurate thinker and
reasoner, that, had the choice depended on the university, he would
have been the new professor of chemistry. He had now, in 1766, greatly
added to his claim of merit by his important discovery of latent heat;
and he had acquired the esteem of all by the singular moderation and
scrupulous caution which marked all his researches.
Dr. Black was appointed to the chemical chair in Edinburgh in 1766, to
the general satisfaction of the public, but the University of Glasgow
suffered an irreparable loss. In this new situation his talents were
more conspicuous and more extensively useful. He saw that the case was
so, and while he could not but be gratified by the number of students
whom the high reputation of Edinburgh, as a medical school, brought
together, his mind was forcibly struck by the importance of his duties
as a teacher. This led him to form the resolution of devoting the
whole of his study to the improvement of his pupils in the elementary
knowledge of chemistry. Many of them came to his class with a very
scanty stock of previous knowledge. Many from the workshop of the
manufacturer had little or none. He was conscious that the number
of this kind of pupils must increase with the increasing activity
and prosperity of the country; and they appeared to him by no means
the least important part of his auditory. To engage the attention of
such pupils, and to be perfectly understood by the most illiterate
of his audience, Dr. Black considered as a sacred duty: he resolved,
therefore, that plain doctrines taught in the plainest manner, should
henceforth employ his chief study. To render his lectures perfectly
intelligible they were illustrated by suitable experiments, by the
exhibition of specimens, and by the repetition of chemical processes.
To this method of lecturing Dr. Black rigidly adhered, endeavouring
every year to make his courses more plain and familiar, and
illustrating them by a greater variety of examples in the way of
experiment. No man could perform these more neatly or successfully;
they were always ingeniously and judiciously contrived, clearly
establishing the point in view, and were never more complicated than
was sufficient for the purpose. Nothing that had the least appearance
of quackery; nothing calculated to surprise and astonish his audience;
nothing savouring of a showman or sleight-of-hand man was ever
permitted in his lecture-room. Every thing was simple, neat, and
elegant, calculated equally to please and to inform: indeed simplicity
and neatness stamped his character. It was this that constituted the
charm of his lectures, and rendered them so delightful to his pupils.
I can speak of them from experience, for I was fortunate enough to
hear the last course of lectures which he ever delivered. I can say
with perfect truth that I never listened to any lectures with so
much pleasure as to his: and it was the elegant simplicity of his
manner, the perfect clearness of his statements, and the vast quantity
of information which he contrived in this way to communicate, that
delighted me. I was all at once transported into a new world--my views
were suddenly enlarged, and I looked down from a height which I had
never before reached; and all this knowledge was communicated without
any apparent effort either on the part of the professor or his pupils.
His illustrations were just sufficient to answer completely the object
in view, and nothing more. No quackery, no trickery, no love of mere
dazzle and glitter, ever had the least influence upon his conduct. He
constituted the most complete model of a perfect chemical lecturer that
I have ever had an opportunity of witnessing.
The discovery which Dr. Black had made that marble is a combination
of lime and a peculiar substance, to which he gave the name of _fixed
air_, began gradually to attract the attention of chemists in other
parts of the world. It was natural in the first place to examine the
nature and properties of this fixed air, and the circumstances under
which it is generated. It may seem strange and unaccountable that Dr.
Black did not enter with ardour into this new career which he had
himself opened, and that he allowed others to reap the corn after
having himself sown the grain. Yet he did take some steps towards
ascertaining the properties of _fixed air_; though I am not certain
what progress he made. He knew that a candle would not burn in it,
and that it is destructive to life, when any living animal attempts
to breathe it. He knew that it was formed in the lungs during the
breathing of animals, and that it is generated during the fermentation
of wine and beer. Whether he was aware that it possesses the properties
of an acid I do not know; though with the knowledge which he possessed
that it combines with alkalies and alkaline earths, and neutralizes
them, or at least blunts and diminishes their alkaline properties,
the conclusion that it partook of alkaline properties was scarcely
avoidable. All these, and probably some other properties of _fixed air_
he was in the constant habit of stating in his lectures from the very
commencement of his academical career; though, as he never published
anything on the subject himself, it is not possible to know exactly
how far his knowledge of the properties of _fixed air_ extended. The
oldest manuscript copy of his lectures that I have seen was taken
down in writing in the year 1773; and before that time Mr. Cavendish
had published his paper on _fixed air_ and _hydrogen gas_, and had
detailed the properties of each. It was impossible from the manuscript
of Dr. Black’s lectures to know which of the properties of _fixed air_
stated by him were discovered by himself, and which were taken from Mr.
Cavendish.
This languor and listlessness, on the part of Dr. Black, is chiefly to
be ascribed to the delicate state of his health, which precluded much
exertion, and was particularly inconsistent with any attempt at putting
his thoughts down upon paper. Hence, probably, that carelessness
about posthumous fame, and that regardlessness of reputation, which,
however it may be accounted for from bodily ailment, must still be
considered as a blemish. How differently did Paschal act in a similar
state of health! With what energy did he exert himself in spite of
bodily ailment! But the tone of his mind was quite different from that
of Dr. Black. Gentleness, diffidence, and perhaps even slowness of
apprehension, were the characteristic features by which the latter was
distinguished.
There is an anecdote of Black which I was told by the late Mr. Benjamin
Bell, of Edinburgh, author of a well-known system of surgery, and
he assured me that he had it from the late Sir George Clarke, of
Pennicuik, who was a witness of the circumstance related. Soon after
the appearance of Mr. Cavendish’s paper on hydrogen gas, in which he
made an approximation to the specific gravity of that body, showing
that it was at least ten times lighter than common air, Dr. Black
invited a party of his friends to supper, informing them that he had
a curiosity to show them. Dr. Hutton, Mr. Clarke of Elden, and Sir
George Clarke of Pennicuik, were of the number. When the company
invited had assembled, he took them into a room. He had the allentois
of a calf filled with hydrogen gas, and upon setting it at liberty,
it immediately ascended, and adhered to the ceiling. The phenomenon
was easily accounted for: it was taken for granted that a small black
thread had been attached to the allentois, that this thread passed
through the ceiling, and that some one in the apartment above, by
pulling the thread, elevated it to the ceiling, and kept it in this
position. This explanation was so probable, that it was acceded to
by the whole company; though, like many other plausible theories, it
turned out wholly unfounded; for when the allentois was brought down no
thread whatever was found attached to it. Dr. Black explained the cause
of the ascent to his admiring friends; but such was his carelessness
of his own reputation, and of the information of the public, that he
never gave the least account of this curious experiment even to his
class; and more than twelve years elapsed before this obvious property
of hydrogen gas was applied to the elevation of air-balloons, by M.
Charles, in Paris.
The constitution of Dr. Black had always been exceedingly delicate. The
slightest cold, the most trifling approach to repletion, immediately
affected his chest, occasioned feverishness, and if the disorder
continued for two or three days, brought on a spitting of blood.
In this situation, nothing restored him to ease, but relaxation of
thought, and gentle exercise. The sedentary life to which study
confined him, was manifestly hurtful; and he never allowed himself to
indulge in any investigation that required intense thought, without
finding these complaints increased.
Thus situated, Dr. Black was obliged to be a contented spectator of the
rapid progress which chemistry was making, without venturing himself to
engage in any of the numerous investigations which presented themselves
on every side. Such indeed was the eagerness with which chemistry was
at that time prosecuted, and such the passion for discovery, that there
was some risk that his undoubted claim to originality and priority
in his own great discoveries, might be called in question, and even
rendered doubtful. His friends at least were afraid of this, and often
urged him to do justice to himself, by publishing an account of his
own discoveries. He more than once began the task; but was so nice in
his notions of the manner in which it should be executed, that the
pains he took in forming a plan of the work never failed to affect
his health, and oblige him to desist. It is known that he felt hurt
at the publication of several of Lavoisier’s papers, in the Mémoires
de l’Académie, without any allusion whatever to what he himself had
previously done on the same subject. How far Lavoisier was really
culpable, and whether he did not intend to do full justice to all the
claims of his predecessors, cannot now be known; as he was cut off
in the midst of his career, while so many of his scientific projects
remained unexecuted. From the posthumous works of Lavoisier, there
is some reason for believing that if he had lived, he would have
done justice to all parties; but there is no doubt that Dr. Black,
in the mean time, thought himself aggrieved, and that he formed the
intention of doing himself justice, by publishing an account of his own
discoveries; however this intention was thwarted and prevented by bad
health.
No one contributed more largely to establish, to support, and to
increase, the high character of the medical school in the University
of Edinburgh than Dr. Black. His talent for communicating knowledge
was not less eminent than his faculty of observation. He soon became
one of the principal ornaments of the university; and his lectures
were attended by an audience which continued increasing from year to
year for more than thirty years. His personal appearance and manners
were those of a gentleman, and peculiarly pleasing: his voice, in
lecturing, was low, but fine; and his articulation so distinct, that he
was perfectly well heard by an audience consisting of several hundreds.
While in Glasgow, he had practised extensively as a physician; but in
Edinburgh he declined general practice, and confined his attendance to
a few families of intimate and respected friends. He was, however, a
physician of good repute in a place where the character of a physician
implied no common degree of liberality, propriety, and dignity of
manners, as well as of learning and skill.
Such was Dr. Black as a public man. While young, his countenance was
comely and interesting; and as he advanced in years, it continued to
preserve that pleasing expression of inward satisfaction which, by
giving ease to the beholder, never fails to please. His manners were
simple, unaffected, and graceful; he was of the most easy approach,
affable, and readily entered into conversation, whether serious
or trivial: for he was not merely a man of science, but was well
acquainted with the elegant accomplishments. He had an accurate musical
ear, and a voice which would obey it in the most perfect manner; he
sang and performed on the flute with great taste and feeling; and could
sing a plain air at sight, which many instrumental performers cannot
do. Music was his amusement in Glasgow; after his removal to Edinburgh
he gave it up entirely. Without having studied drawing he had acquired
a considerable power of expression with his pencil, both in figures
and in landscape. He was peculiarly happy in expressing the passions,
and seemed in this respect to have the talents of a historical
painter. Figure indeed, of every kind, attracted his attention; in
architecture, furniture, ornament of every sort, it was never a matter
of indifference to him. Even a retort, or a crucible, was to his eye
an example of beauty, or deformity. These are not indifferent things;
they are features of an elegant mind, and they account for some part of
that satisfaction and pleasure which persons of different habits and
pursuits felt in Dr. Black’s company and conversation.
Those circumstances of form, and in which Dr. Black perceived or sought
for beauty, were suitableness or propriety: something that rendered
them well adapted for the purposes for which they were intended. This
love of propriety constituted the leading feature in Dr. Black’s mind;
it was the standard to which he constantly appealed, and which he
endeavoured to make the directing principle of his conduct.
Dr. Black was fond of society, and felt himself beloved in it. His
chief companions, in the earlier part of his residence in Edinburgh,
were Dr. Adam Smith, Mr. David Hume, Dr. Adam Ferguson, Mr. John Home,
Dr. Alexander Carlisle, and a few others. Mr. Clarke of Elden, and his
brother Sir George, Dr. Roebuck, and Dr. James Hutton, particularly
the latter, were affectionately attached to him, and in their society
he could indulge in his professional studies. Dr. Hutton was the
only person near him to whom Dr. Black imparted every speculation in
chemical science, and who knew all his literary labours: seldom were
the two friends asunder for two days together.
Towards the close of the eighteenth century, the infirmities of
advanced life began to bear more heavily on his feeble constitution.
Those hours of walking and gentle exercise, which had hitherto
been necessary for his ease, were gradually curtailed. Company and
conversation began to fatigue: he went less abroad, and was visited
only by his intimate friends. His duty at college became too heavy for
him, and he got an assistant, who took a share of the lectures, and
relieved him from the fatigue of the experiments. The last course of
lectures which he delivered was in the winter of 1796-7. After this,
even lecturing was too much for his diminished strength, and he was
obliged to absent himself from the class altogether; but he still
retained his usual affability of temper, and his habitual cheerfulness,
and even to the very last was accustomed to walk out and take
occasional exercise. As his strength declined, his constitution became
more and more delicate. Every cold he caught occasioned some degree of
spitting of blood; yet he seemed to have this unfortunate disposition
of body almost under command, so that he never allowed it to proceed
far, or to occasion any distressing illness. He spun his thread of
life to the very last fibre. He guarded against illness by restricting
himself to an abstemious diet; and he met his increasing infirmities
with a proportional increase of attention and care, regulating his food
and exercise by the measure of his strength. Thus he made the most of a
feeble constitution, by preventing the access of disease from abroad.
And enjoyed a state of health which was feeble, indeed, but scarcely
interrupted; as well as a mind undisturbed in the calm and cheerful use
of its faculties. His only apprehension was that of a long-continued
sick-bed--from the humane consideration of the trouble and distress
that he might thus occasion to attending friends; and never was such
generous wish more completely gratified than in his case.
On the 10th of November, 1799, 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 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 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 halfway to 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 was sometimes wont
to happen after 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 he again returned,
and coming close up to him, he found him without life. His very near
neighbour, Mr. Benjamin Bell, the surgeon, was immediately sent for;
but nothing whatever could be done.[185]
[185] The preceding character of Dr. Black is from Professor Robison,
who knew him intimately; and from Dr. Adam Ferguson, who was his next
relation. See the preface to Dr. Black’s lectures. The portrait of Dr.
Black prefixed to these lectures is an excellent likeness.
Dr. Black’s writings are exceedingly few, consisting altogether of
no more than three papers. The first, entitled “Experiments upon
Magnesia alba, Quicklime, and other Alkaline Substances,” constituted
the subject of his inaugural dissertation. It afterwards appeared
in an English dress in one of the volumes of The Edinburgh Physical
and Literary Essays, in the year 1755. Mr. Creech, the bookseller,
published it in a separate pamphlet, together with Dr. Cullen’s
little essay on the “cold produced by evaporating fluids,” in the
year 1796. This essay exhibits one of the very finest examples of
inductive reasoning to be found in the English language. The author
shows that magnesia is a peculiar earthy body, possessed of properties
very different from lime. He gives the properties of lime in a pure
state, and proves that it differs from limestone merely by the absence
of the carbonic acid, which is a constituent of limestone. Limestone
is a _carbonate of lime_; quicklime is the pure uncombined earth. He
shows that magnesia has also the property of combining with carbonic
acid; that caustic potash, or soda, is merely these bodies in a pure
or isolated state; while the mild alkalies are combinations of these
bodies with carbonic acid. The reason why quicklime converts mild
into caustic alkali is, that the lime has a stronger affinity for
the carbonic acid than the alkali; hence the lime is converted into
carbonate of lime, and the alkali, deprived of its carbonic acid,
becomes caustic. Mild potash is a carbonate of potash; caustic potash,
is potash freed from carbonic acid.--The publication of this essay
occasioned a controversy in Germany, which was finally settled by
Jacquin and Lavoisier, who repeated Dr. Black’s experiments and showed
them to be correct.
Dr. Black’s second paper was published in the Philosophical
Transactions for 1775. It is entitled “The supposed Effect of boiling
on Water, in disposing it to freeze more readily, ascertained by
Experiments.” He shows, that when water that has been recently boiled
is exposed to cold air, it begins to freeze as soon as it reaches the
freezing point; while water that has not been boiled may be cooled some
degrees below the freezing point before it begins to congeal. But if
the unboiled water be constantly stirred during the whole time of its
exposure, it begins to freeze when cooled down to the freezing point as
well as the other. He shows that the difference between the two waters
consists in this, that the boiled water is constantly absorbing air,
which disturbs it, whereas the other water remains in a state of rest.
His last paper was “An Analysis of the Water of some boiling Springs
in Iceland,” published in the Transactions of the Royal Society of
Edinburgh. This was the water of the Geyser spring, brought from
Iceland by Sir J. Stanley. Dr. Black found it to contain a great deal
of silica, held in solution in the water by caustic soda.
The tempting career which Dr. Black opened, and which he was unable to
prosecute for want of health, soon attracted the attention of one of
the ablest men that Great Britain has produced--I mean Mr. Cavendish.
The Honourable Henry Cavendish was born in London on the 10th of
October, 1731: his father was Lord Charles Cavendish, a cadet of the
house of Devonshire, one of the oldest families in England. During his
father’s lifetime he was kept in rather narrow circumstances, being
allowed an annuity of £500 only; while his apartments were a set of
stables, fitted up for his accommodation. It was during this period
that he acquired those habits of economy, and those singular oddities
of character, which he exhibited ever after in so striking a manner. At
his father’s death he was left a very considerable fortune; and an aunt
who died at a later period bequeathed him a very handsome addition to
it; but, in consequence of the habits of economy which he had acquired,
it was not in his power to spend the greater part of his annual income.
This occasioned a yearly increase to his capital, till at last it
accumulated so much, without any care on his part, that at the period
of his death he left behind him nearly £1,300,000; and he was at that
time the greatest proprietor of stock in the Bank of England.
On one occasion, the money in the hands of his bankers had accumulated
to the amount of £70,000. These gentlemen thinking it improper to keep
so large a sum in their hands, sent one of the partners to wait upon
him, in order to learn how he desired it disposed of. This gentleman
was admitted; and, after employing the necessary precautions to a man
of Mr. Cavendish’s peculiar disposition, stated the circumstance, and
begged to know whether it would not be proper to lay out the money at
interest. Mr. Cavendish dryly answered, “You may lay it out if you
please,” and left the room.
He hardly ever went into any other society than that of his scientific
friends: he never was absent from the weekly dinner of the Royal
Society club at the Crown and Anchor Tavern in the Strand. At these
dinners, when he happened to be seated near those that he liked, he
often conversed a great deal; though at other times he was very silent.
He was likewise a constant attendant at Sir Joseph Banks’s Sunday
evening meetings. He had a house in London, which he only visited
once or twice a-week at stated times, and without ever speaking to
the servants: it contained an excellent library, to which he gave all
literary men the freest and most unrestrained access. But he lived
in a house on Clapham Common, where he scarcely ever received any
visitors. His relation, Lord George Cavendish, to whom he left by will
the greatest part of his fortune, visited him only once a-year, and the
visit hardly ever exceeded ten or twelve minutes.
He was shy and bashful to a degree bordering on disease; he could not
bear to have any person introduced to him, or to be pointed out in any
way as a remarkable man. One Sunday evening he was standing at Sir
Joseph Banks’s in a crowded room, conversing with Mr. Hatchett, when
Dr. Ingenhousz, who had a good deal of pomposity of manner, came up
with an Austrian gentleman in his hand, and introduced him formally to
Mr. Cavendish. He mentioned the titles and qualifications of his friend
at great length, and said that he had been peculiarly anxious to be
introduced to a philosopher so profound and so universally known and
celebrated as Mr. Cavendish. As soon as Dr. Ingenhousz had finished,
the Austrian gentleman began, and assured Mr. Cavendish that his
principal reason for coming to London was to see and converse with one
of the greatest ornaments of the age, and one of the most illustrious
philosophers that ever existed. To all these high-flown speeches Mr.
Cavendish answered not a word, but stood with his eyes cast down quite
abashed and confounded. At last, spying an opening in the crowd, he
darted through it with all the speed of which he was master; nor did he
stop till he reached his carriage, which drove him directly home.
Of a man, whose habits were so retired, and whose intercourse with
society was so small, there is nothing else to relate except his
scientific labours: the current of his life passed on with the utmost
regularity; the description of a single day would convey a correct idea
of his whole existence. At one time he was in the habit of keeping
an individual to assist him in his experiments. This place was for
some time filled by Sir Charles Blagden; but they did not agree well
together, and after some time Sir Charles left him. Mr. Cavendish died
on the 4th of February, 1810, aged seventy-eight years, four months,
and six days. When he found himself dying, he gave directions to his
servant to leave him alone, and not to return till a certain time which
he specified, and by which period he expected to be no longer alive.
The servant, however, who was aware of the state of his master, and
was anxious about him, opened the door of the room before the time
specified, and approached the bed to take a look at the dying man. Mr.
Cavendish, who was still sensible, was offended at the intrusion, and
ordered him out of the room with a voice of displeasure, commanding him
not by any means to return till the time specified. When he did come
back at that time, he found his master dead. What a contrast between
the characters of Mr. Cavendish and Dr. Black!
The appearance of Mr. Cavendish did not much prepossess strangers in
his favour; he was somewhat above the middle size, his body rather
thick, and his neck rather short. He stuttered a little in his speech,
which gave him an air of awkwardness: his countenance was not strongly
marked, so as to indicate the profound abilities which he possessed.
This was probably owing to the total absence of all the violent
passions. His education seems to have been very complete; he was an
excellent mathematician, a profound electrician, and a most acute
and ingenious chemist. He never ventured to give an opinion on any
subject, unless he had studied it to the bottom. He appeared before
the world first as a chemist, and afterwards as an electrician. The
whole of his literary labours consist of eighteen papers, published
in the Philosophical Transactions, which, though they occupy only a
few pages, are full of the most important discoveries and the most
profound investigations. Of these papers, there are ten which treat
of chemical subjects, two treat of electricity, two of meteorology,
three are connected with astronomy, and there is one, the last which
he wrote, which gives his method of dividing astronomical instruments.
Of the papers in question, those alone which treat of Chemistry can be
analyzed in a work like this.
1. His first paper, entitled, “Experiments on fictitious Air,” was
published in the year 1766, when Mr. Cavendish was thirty-five years
of age. Dr. Hales had demonstrated (as had previously been done by
Van Helmont and Glauber) that _air_ is given out by a vast number of
bodies in peculiar circumstances. But he never suspected that any of
the _airs_ which he obtained differed from common air. Indeed common
air had always been considered as an elementary substance to which
every elastic fluid was referred. Dr. Black had shown that the mild
alkalies and limestone, and carbonate of magnesia, were combinations
of these bodies with a gaseous substance, to which he had given
the name of _fixed air_; and he had pointed out various methods of
collecting this fixed air; though he himself had not made much progress
in investigating its properties. This paper of Mr. Cavendish may be
considered as a continuation of the investigations begun by Dr. Black.
He shows that there exist two species of air quite different in their
properties from common air: and he calls them _inflammable air_ and
_fixed air_.
Inflammable air (hydrogen gas) is evolved when iron, zinc, or tin,
are dissolved in dilute sulphuric or muriatic acid. Iron yielded
about 1-22d part of its weight, of inflammable air, zinc about
1-23d or 1-24th of its weight, and tin about 1-44th of its weight.
The properties of the inflammable air were the same, whichever of
the three metals was used to procure it, and whether they were
dissolved in sulphuric or muriatic acids. When the sulphuric acid was
concentrated, iron and zinc dissolved in it with difficulty and only
by the assistance of heat. The air given out was not inflammable, but
consisted of sulphurous acid. These facts induced Mr. Cavendish to
conclude that the inflammable air evolved in the first case was the
unaltered _phlogiston_ of the metals, while the sulphurous acid evolved
in the second case, was a compound of the same phlogiston and a portion
of the acid, which deprived it of its inflammability. This opinion was
very different from that of Stahl, who considered combustible bodies as
compounds of phlogiston with acids or calces.
Cavendish found the specific gravity of his inflammable air about
eleven times less than that of common air. This determination is under
the truth; but the error is, at least in part, owing to the quantity
of water held in solution by the air, and which, as Mr. Cavendish
showed, amounted to about 1-9th of the weight of the air. He tried
the combustibility of the inflammable air, when mixed with various
proportions of common air, and found that it exploded with the greatest
violence when mixed with rather more than its bulk of common air.
Copper he found, when dissolved in muriatic acid by the assistance of
heat, yielded no inflammable air, but an air which lost its elasticity
when it came in contact with water. This _air_, the nature of which Mr.
Cavendish did not examine, was _muriatic acid gas_, the properties of
which were afterwards investigated by Dr. Priestley.
The _fixed air_ (_carbonic acid gas_) on which Mr. Cavendish made his
experiments was obtained by dissolving marble in muriatic acid. He
found that it might be kept over mercury for any length of time without
undergoing any alteration; that it was gradually absorbed by cold
water; and that 100 measures of water of the temperature 55° absorbed
103·8 measures of fixed air. The whole of the air thus absorbed was
separated again by exposing the water to a boiling heat, or by leaving
it for sometime in an open vessel. Alcohol (the specific gravity not
mentioned) absorbed 2¼ times its bulk of this air, and olive-oil about
1-3d of its bulk.
The specific gravity of fixed air he found 1·57, that of common air
being 1.[186] Fixed air is incapable of supporting combustion, and
common air, when mixed with it, supports combustion a much shorter time
than when pure. A small wax taper burnt eighty seconds in a receiver
which held 180 ounce measures, when filled with common air only. The
same taper burnt fifty-one seconds in the same receiver when filled
with a mixture of one volume fixed air, and nineteen volumes of common
air. When the fixed air was 3-40ths of the whole volume the taper
burnt twenty-three seconds. When the fixed air was 1-10th, the taper
burnt eleven seconds. When it was 6-55ths or 1-9·16 of the whole
mixture, the taper would not burn at all.
[186] This I apprehend to be a little above the truth, the true
specific gravity of carbonic acid gas being 1·5277, that of air being
unity.
Mr. Cavendish was of opinion that more than one kind of fixed air was
given out by marble; in other words, that the elastic fluid emitted,
consisted of two different airs, one more absorbable by water than
the other. He drew his conclusion from the circumstance that after a
solution of potash had been exposed to a quantity of fixed air for
some time, it ceased to absorb any more; yet, if the residual portion
of air were thrown away and new fixed air substituted in its place, it
began to absorb again; but Mr. Dalton has since given a satisfactory
explanation of this seeming anomaly by showing that the absorbability
of fixed air in water is proportional to its purity, and that when
mixed with a great quantity of common air or any other gas not soluble
in water, it ceases to be sensibly absorbed.
Mr. Cavendish ascertained the quantity of fixed air contained in
marble, carbonate of ammonia, common pearlashes, and carbonate of
potash: but notwithstanding the care with which these experiments were
made they are of little value; because the proper precautions could not
be taken, in that infant state of chemical science, to have these salts
in a state of purity. The following were the results obtained by Mr.
Cavendish:
1000 grains of marble contained 408 grs. fixed air.
1000 -- carb. of ammonia 533 --
1000 -- pearlashes 284 --
1000 -- carb. of potash 423 --
Supposing the marble, carbonate of ammonia, and carbonate of potash, to
have been pure anhydrous simple salts, their composition would be
1000 grains of marble contain 440 grs. fixed air.
1000 -- carb. of ammonia 709·6 --
1000 -- carb. of potash 314·2 --
Bicarbonate of potash was first obtained by Dr. Black. Mr. Cavendish
formed the salt by dissolving pearlashes in water, and passing a
current of carbonic acid gas through the solution till it deposited
crystals. These crystals were not altered by exposure to the air, did
not deliquesce, and were soluble in about four times their weight of
cold water.
Dr. M’Bride had already ascertained that vegetable and animal
substances yield fixed air by putrefaction and fermentation. Mr.
Cavendish found by experiment that sugar when dissolved in water
and fermented, gives out 57-100ths of its weight of fixed air,
possessing exactly the properties of fixed air from marble. During
the fermentation no air was absorbed, nor was any change induced on
the common air, at the surface of the fermenting liquor. Apple-juice
fermented much faster than sugar; but the phenomena were the same,
and the fixed air emitted amounted to 381/1000 of the weight of the
solid extract of apples. Gravy and raw meat yielded inflammable air
during their putrefaction, the former in much greater quantity than the
latter. This air, as far as Mr. Cavendish’s experiments went, he found
the same as the inflammable air from zinc by dilute sulphuric acid; but
its specific gravity was a little higher.
This paper of Mr. Cavendish was the first attempt by chemists to
collect the different kinds of air, and endeavour to ascertain their
nature. Hence all his processes were in some measure new: they served
as a model to future experimenters, and were gradually brought to their
present state of simplicity and perfection. He was the first person
who attempted to determine the specific gravity of airs, by comparing
their weight with that of the same bulk of common air; and though
his apparatus was defective, yet the principle was good, and is the
very same which is still employed to accomplish the same object. Mr.
Cavendish then first began the true investigation of gases, and in his
first paper he determined the peculiar nature of two very remarkable
gases, _carbonic_ and _hydrogen_.
2. Mineral waters have at all times attracted the attention of the
faculty in consequence of their peculiar properties and medical
virtues. Some faint steps towards their investigation were taken by
Boyle. Du Clos attempted a chemical analysis of the mineral waters in
France; and Hierne made a similar investigation of the mineral waters
of Sweden. Though these experiments were rude and inaccurate, they
led to the knowledge of several facts respecting mineral waters which
chemists were unable to explain. One of these was the existence of a
considerable quantity of _calcareous earth_ in some mineral waters,
which was precipitated by boiling. Nobody could conceive in what way
this insoluble substance (_carbonate of lime_) was held in solution,
nor why it was thrown down when the water was raised to a boiling
heat. It was to determine this point that Mr. Cavendish made his
experiments on Rathbone-place water, which were published in the year
1767, and which may be considered as the first analysis of a mineral
water that possessed tolerable accuracy. Rathbone-place water was
raised by a pump, and supplied the portion of London in its immediate
neighbourhood. Mr. Cavendish found that when boiled, it deposited a
quantity of earthy matter, consisting chiefly of lime, but containing
also a little magnesia. This he showed was held in solution by fixed
air; and he proved experimentally, that when an excess of this gas
is present, it has the property of holding lime and magnesia in
solution.[187] Besides these earthy carbonates, the water was found to
contain a little ammonia, some sulphate of lime, and some common salt.
Mr. Cavendish examined, likewise, some other pump-water in London, and
showed that it contained lime, held in solution by carbonic acid.
[187] The salts held in solution are in the state of bicarbonates of
lime and magnesia. Boiling drives off half the carbonic acid, and the
simple carbonates being insoluble are precipitated.
3. Dr. Priestley, at a pretty early period of his chemical career,
had discovered that when nitrous gas is mixed with common air over
water, a diminution of bulk takes place; that there is a still greater
diminution of bulk when oxygen gas is employed instead of common
air; and that the diminution is always proportional to the quantity
of oxygen gas present in the gas mixed with the nitrous gas. This
discovery induced him to employ nitrous gas as a test of the quantity
of oxygen present in common air; and various instruments were contrived
to facilitate the mixture of the gases, and the measurement of the
diminution of volume which took place. As the goodness of air, or its
fitness to support combustion, and maintain animal life, was conceived
to depend upon the proportion of oxygen gas which it contained, these
instruments were distinguished by the name of _eudiometers_; the
simplest of them was contrived by Fontana, and is usually distinguished
by the name of the _eudiometer of Fontana_. Philosophers, in examining
air by means of this instrument, at various seasons, and in various
places, had found considerable differences in the diminution of
bulk: hence they inferred that the proportion of oxygen varies in
different places; and to this variation they ascribed the healthiness
or noxiousness of particular situations. For example, Dr. Ingenhousz
had found a greater proportion of oxygen in the air above the sea, and
on the sea-coast; and to this he ascribed the healthiness of maritime
situations. Mr. Cavendish examined this important point with his usual
patient industry and acute discernment, and published the result in the
Philosophical Transactions for 1783. He ascertained that the apparent
variations were owing to inaccuracies in making the experiment; and
that when the requisite precautions are taken, the proportion of oxygen
in air is found constant in all places, and at all seasons. This
conclusion has since been confirmed by numerous observations in every
part of the globe. Mr. Cavendish also analyzed common air, and found it
to consist of
79·16 volumes azotic gas,
20·84 volumes oxygen gas.
------
100·00
4. For many years it was the opinion of chemists that mercury is
essentially liquid, and that no degree of cold is capable of congealing
it. Professor Braun’s accidental discovery that it may be frozen by
cold, like other liquids, was at first doubted; and when it was finally
established by the most conclusive experiments, it was inferred from
the observations of Braun that the freezing point of mercury is several
hundred degrees below zero on Fahrenheit’s scale. It became an object
of great importance to determine the exact point of the congelation
of this metal by accurate experiments. This was done at Hudson’s Bay,
by Mr. Hutchins, who followed a set of directions given him by Mr.
Cavendish, and from his experiments Mr. Cavendish, in a paper inserted
in the Philosophical Transactions for 1783, deduced that the freezing
point of mercury is 38·66 degrees below the zero of Fahrenheit’s
thermometer.
5. These experiments naturally drew the attention of Mr. Cavendish to
the phenomena of freezing, to the action of freezing mixtures, and the
congelation of acids. He employed Mr. M’Nab, who was settled in the
neighbourhood of Hudson’s Bay, to make the requisite experiments; and
he published two very curious and important papers on these subjects
in the Philosophical Transactions for 1786 and 1788. He explained the
phenomena of congelation exactly according to the theory of Dr. Black,
but rejecting the hypothesis that heat is a _substance_ sui generis,
and thinking it more probable, with Sir Isaac Newton, that it is
owing to the rapid internal motion of the particles of the hot body.
The latent heat of water, he found to be 150°. The observations on the
congelation of nitric and sulphuric acids are highly interesting: he
showed that their freezing points vary considerably, according to the
strength of each; and drew up tables indicating the freezing points of
acids, of various degrees of strength.
6. But the most splendid and valuable of Mr. Cavendish’s chemical
experiments were published in two papers, entitled, “Experiments on
Air,” in the Transactions of the Royal Society for 1784 and 1785. The
object of these experiments was to determine what happened during the
_phlogistication of air_, as it was at that time termed; that is, the
change which air underwent when metals were calcined in contact with
it, when sulphur or phosphorus was burnt in it, and in several similar
processes. He showed, in the first place, that there was no reason for
supposing that carbonic acid was formed, except when some animal or
vegetable substance was present; that when _hydrogen gas_ was burnt
in contact with air or oxygen gas, it _combined_ with that gas, and
formed _water_; that _nitrous gas_, by combining with the oxygen of the
atmosphere, formed _nitrous acid_; and that when _oxygen_ and _azotic_
gas are mixed in the requisite proportions, and electric sparks passed
through the mixture, they _combine_, and form _nitric_ acid.
The first of these opinions occasioned a controversy between Mr.
Cavendish, and Mr. Kirwan, who maintained that carbonic acid is always
produced when air is phlogisticated. Two papers on this subject by
Kirwan, and one by Cavendish, are inserted in the Philosophical
Transactions for 1784, each remarkable examples of the peculiar manner
of the respective writers. All the arguments of Kirwan are founded on
the experiments of others. He displays great reading, and a strong
memory; but does not discriminate between the merits of the chemists
on whose authority he founds his opinions. Mr. Cavendish, on the other
hand, never advances a single opinion, which he has not put to the
test of experiment; and never suffers himself to go any further than
his experiment will warrant. Whatever is not accurately determined
by unexceptionable trials, is merely stated as a conjecture on which
little stress is laid.
In the first of these celebrated papers, Mr. Cavendish has drawn a
comparison between the phlogistic and antiphlogistic theories of
chemistry; he has shown that each of them is capable of explaining
the phenomena in a satisfactory manner; though it is impossible to
demonstrate the truth of either; and he has given the reasons which
induced him to prefer the phlogistic theory--reasons which the French
chemists were unable to refute, and which they were wise enough not
to notice. There cannot be a more striking proof of the influence of
fashion, even in science, and of the unwarrantable precipitation with
which opinions are rejected or embraced by philosophers, than the total
inattention paid by the chemical world to this admirable dissertation.
Had Mr. Kirwan adopted the opinions of Mr. Cavendish, when he undertook
the defence of phlogiston, instead of trusting to the vague experiments
of inaccurate chemists, he would not have been obliged to yield to his
French antagonists, and the antiphlogistic theory would not so speedily
have gained ground.
Such is an epitome of the chemical papers of Mr. Cavendish. They
contain five notable discoveries; namely, 1. The nature and properties
of hydrogen gas. 2. The solubility of bicarbonates of lime and magnesia
in water. 3. The exact proportion of the constituents of common air. 4.
The composition of water. 5. The composition of nitric acid. It is to
him also that we are indebted for our knowledge of the freezing point
of mercury; and he was likewise the first person who showed that potash
has a stronger affinity for acids than soda has. His experiments on the
subject are to be found in a paper on Mineral Waters, published in the
Philosophical Transactions, by Dr. Donald Monro.
END OF VOL. I.
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most esteemed authors of Greece and Rome, but possess not the means or
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must prove a valuable acquisition. The following are the contents of
the volumes already published.
No. I.--DEMOSTHENES (translated by Dr. Leland), comprising a sketch of
the Life of Demosthenes: his Orations against Philip, King of Macedon;
and those pronounced on occasions of public deliberation.
No. II.--DEMOSTHENES, concluded, and SALLUST complete: (the latter
translated by William Rose, M. A.) comprising the Orations of
Dinarchus against Demosthenes, and Account of the Exile and Death of
Demosthenes, and the Orations of Æschines and Demosthenes on the Crown:
a Biographical Sketch of SALLUST: his History of Catiline’s
conspiracy; and History of the Roman War against Jugurtha, King of
Numidia.
No. III.--XENOPHON, Vol. I. (translated by E. Spelman, Esq.),
comprising a Biographical Sketch of the Historian; and his Anabasis, or
Expedition of Cyrus into Persia, and retreat of the 10,000 Greeks.
No. IV.--XENOPHON, vol. II. (translated by the Hon. Maurice Ashley
Cooper), comprising the Cyropædia, or the Education, Life and Manners,
Government, Wars, and Achievements of Cyrus, King of Persia.
No. V.--HERODOTUS, vol. I. (translated by the Rev. W. Beloe),
comprising a Biographical Sketch of the Historian; and the first two
Books of his History, containing a Narrative of the Acquisition of
the Kingdom of Lydia by Crœsus, and the subsequent overthrow of the
Lydian Empire by Cyrus; the early History of the Republics of Athens
and Lacedæmon; with an account of Egypt, its Customs, Manners, and
Governments.
No. VI.--HERODOTUS, vol II., comprising, in the 3d, 4th, and 5th Books,
the Exploits of Cambyses, with the subjugation of the whole of Egypt;
the elevation of Darius Hystaspes to the Persian throne; the disastrous
Expeditions of the Persians against the Scythians during his reign; the
progress of the Republics of Athens, Lacedæmon and Corinth, and their
state during the time of the Persian Emperor Darius.
No. VII.--HERODOTUS, vol. III., comprising, in the 6th to the 9th Book,
the Origin of the Lacedæmonian Kings; the first Invasion of Greece
by the Persians; the Battle of Marathon; the memorable Expedition of
Xerxes into Greece; the Battle of Thermopylæ; the Capture and Burning
of Athens by the Persians; the Sea-fight of Salamis; the Battles of
Platæa and of the Promontory of Mycale; and the overthrow of the
Persian power in Greece.
No. VIII.--VIRGIL, vol. I., comprising a Biographical Sketch of the
Poet; his _Eclogues_, or Pastoral Poems, translated by Archdeacon
Wrangham; the _Georgics_, or Poems on Husbandry, translated by William
Sotheby, Esq.; and the first two Books of the _Æneid_, translated by
Dryden, and prefaced with his celebrated Dedication.
No. IX.--VIRGIL, vol. II., comprising the remainder of Dryden’s
translation of the _Æneid_, namely, from the third to the twelfth Book.
No. X.--PINDAR (translated by the Rev. C. A. Wheelwright, Prebendary of
Lincoln); and ANACREON, by Mr. Thomas Bourne.
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[Transcriber’s Note:
Inconsistent spelling and hyphenation are as in the original.
Page 51: “zeb” changed to read “zahav”.
Page 53: “kemep” changed to read “keseph”.
Page 54: “necheshet” changed to read “nechooshat”.
Page 63: “berezel” changed to read “barzel”.
Page 63: “ber” changed to read “bar”.
Page 63: “nezel” changed to read “nazal”.
Page 76: “arrenichon” changed to read “arrhenichon”.
Page 81: “chuanos” changed to read “kyanos”.]