Thomas Reid.

The works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters online

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different colours much more than another
composition, even with the same degree of
refraction. Dollond has made a fortune by
his telescopes, nobody else having attempted
to imitate them, and is now, I am told,
grown lazy. Nor is the theory of them
prosecuted as it ought. Dollond's micro-
meter is likewise a very fine instrument,
although not built upon anything new in
opticks. We have one of them here fitted to
a reflecting telescope of about 18 inches,
by which one may take the apparent diame-
ter of the sun, or of any planet, within a
second of a degree.

I find a variety of things here to amuse
me in the literary world, and want nothing
so much as my old friends, whose place I
cannot expect, at my time of life, to sup-
ply. I think the common people here and
in the neighbourhood greatly inferior to
the common people with you. They are
Boeotian in their understandings, fanatical
in their religion, and clownish in their dress
and manners. The clergy encourage this
fanaticism too much, and find it the only
way to popularity. I often hear a gospel
here which you know nothing about; for
you neither hear it from the pulpit, nor
will you find it in the bible.

What is your Philosophical Society* do-
ing ? Still battling about D. Hume ? or
have you time to look in ? I hope your
papa holds out in his usual way. I beg to
be remembered to him most affectionately,
and to all the rest of your family. But I
believe you do not like to be charged with
compliments, otherwise I would desire of
you likewise to remember me respectfully
to Sir Archibald Grant, Sir Arthur and
Lady Forbes, and others of my country

« The Philosophical Society to which Reid here
al udes was founded by himself and his relative, I)v
John Gregory. It was vulgarly styled the Wine
Club. Dr David Skene, who is called by Sir W.
F. rbes " a prnsic'an ot genius and taste," was one
of its original members, tee Forties's " Life of Beau
tie," i. 35— H.



acquaintance, when you have occasion to
see them. I should be glad, too, to hear
from you, when leisure, and opportunity, and
the epistolary humour all meet together.
My folks are' all pretty well, and beg their
compliments to you and all yours. — I am,
dear Sir, most affectionately, yours,

Thomas Reid.
Glasgow, 13 Jnh/ 1765,
being the first warm day we
have had since the month of



Glasgow, 20 Dec. 17«5.

Dear Sir, — Your commissions have
been lying by me some time, for want of a
proper conveyance. An Aberdeen carrier
promised to call for them, but disappointed
me ; I therefore sent the two thermometers
wrapt up in paper, and directed for you
by Mr. Menzies, merchant in the Narrow
Wynd, who was to set out from hence yes-
terday morning. One has a circular bore
in the small tube, the other an elliptical
one, and is on that account much fitter for
experiments. As there is a much greater
quantity of quicksilver in the circular one,
it may take four or five minutes to bring it
to the temperature of a fluid in which it
is immersed. For nice experiments, some
of the elliptical ones are made by Dr Wil-
son with the bulb of the small tube naked.
But these are so liable to accidents that
few choose them. The perspective machine
goes to Edinburgh to-morrow with Dr Trail,
who will send it to my sisters to be sent you
by the first proper opportunity. . . .

Mr Watt has made two small improve-
ments of the steam-engine. The first is in
the iron bars which support the fire. These
have always been made of solid iron, and
burn away so fast by the great heat, that the
expense of repairing them comes to be very
considerable. He uses hollow square bars
of plate iron, always kept full of water,
which communicates with a pretty large
reservoir, so that the bars can never be
heated above the degree of boyling water,
and may be kept far below that degree of
heat. The other improvement is to pre-
vent the waste of heat by the chimney pipe
of the furnace. It is evident that a very
large proportion of the heat of the fire
passes off in this way without being applied
to the water in the boyler. To prevent
this, he makes three small chimney pipes
of iron, which are made to pass through the
boyler. He is just now employed in setting
up an engine for the Carron Company with
these imp] ovements.

Since I saw C. Carburi, I have it upon
good authority that there are petrifying
springs in England which petrify things
put into them in a short time. And a
gentleman here expects, in a short time, a
petrified periwig from one of them.

Dr Black tells me that Cramer's fur-
naces, both for essaying and melting, as
you have them described in his "Ars Dnci-
masticn," are the best he knows. His are
of this kind, being made of plate iron,
lined with a coat of a lute, which is com-
posed of one-part clay and three-parts fire-
sand, which, he says, never cracks. He
has not examined the Fechel earth, but con-
jectures it to be a composition of the same
kind with Prussian blue. He has seen a
horse's head, which, by being long buried in
a clay which had some mixture of iron, had
in several places taken a fine blue tinge, or
rather was covered with a fine blue dust.

I have attended Dr Black's lectures hith-
erto. His doctrine of latent heat is the
only thing I have yet heard that is alto-
gether new. And, indeed, I look upon it
as a very important discovery. As Mr
Ogilvie attended him and took notes, I
believe he can give you a fuller account of
it than I can. It gives a great deal of light
to the phsenomena of heat that appear in
mixture, solution, and evaporation ; but, as
far as I see, it gives no light to those which
appear in animal heat, inflammation, and
friction. I wish this discovery may not
reach any person who may be so ungene-
rous as to make it public before the Dr
has time to publish it himself. If the ac-
count which Ogilvie can give you should
suggest any doubts, I will be glad to clear
them, so far as my knowledge of this doc-
trine reaches. — I am very glad to hear that
Dr Hope has a prospect of raising the true
rhubarb. I believe I forgot to tell you that I
wrapped up a head of what I take to be the
daucus sylvesiris, in a piece of paper, and
put it in the box with the drawing machine.
It grows in great plenty in the fields here ;
but I never saw it with you. I have not
met with any botanists here.

Our College is considerably more crowded
than it was last session. My class, indeed,
is much the same as last year ; but all the
rest are better. I believe the number of
our students, of one kind or another, may
be between four and five hundred. But the
College of Edinburgh is increased this year
much more than we are. The Moral
Philosophy class there, is more than double
ours. The Professor, Ferguson, is, indeed,
as far as I can judge, a man of a noble spirit,
of very elegant manners, and has a very
uncommon flow of eloquence. I hear he is
about to publish, I don't know under what
title, a natural history of man : exhibiting
a view of him in the savage state, and in



the several successive states of pasturage,
agriculture, and commerce.

Your friend, the Cte. de Lauraguais,
was very full of you when he was here, and
shewed an anxiety that your merit should
be known. I am told that he has wrote
many things in the Memoirs of the Academy ;
but I know nobody here that has read them.
Our College Library is ten or twelve years
behind in the Memoirs of the Royal Aca-
demy ; and all that the Cte. has wrote must
fall within that period. He seems to have
attached himself so entirely to chemistry
as to have neglected every other branch of
knowledge. Carburi was more universal ;
he gave attention chiefly to the progress of
manufactures and commerce, and to col-
lect books and specimens of natural or artifi-
cial things.

Our society is not so harmonious as I
wish. Schemes of interest, pushed by some
and opposed by others, are like to divide us
into parties, and, perhaps, engage us in
law-suits.* When you see Mr W. Ogilvie,
please make my compliments to him. I
received his letter, and will write him when
I can find leisure. I hope your papa is
quite recovered of his cold, and that all the
rest of the family are in good health. Pray,
make my best compliments to him. Mrs
Reid, Pegie, and I, have all had a severe cold
and cough. I have been keeping the house
these two days, in order to get the better of
it. — I am, dear Sir,

Yours most affectionately,

Thomas Reid.

Ended, Dec. 30.

Wishing you many happy years.



Dear Sir, — I have been sometimes apt
to impute it to laziness, and sometimes to
hurry of business, that I have been so long
without writing you. I am ashamed to
plead the last of these excuses when I con-
sider how many people there are of my
acquaintance that have a great deal more
to do than I have, a-nd would think all my
business but idleness. Yet, I assure you,
I can rarely find an hour which I am at
liberty to dispose of as I please. The most
disagreeable thing in the teaching part is to
have a great number of stupid Irish teagues
who attend classes for two or three years
to qualify them for teaching schools, or
being dissenting teachers. I preach to
these as St Francis did to the fishes.-)- I

• See above, p 40, A, below, pp. 46, A, and47, B.
AH theory and all experience prove, that the worst
and the most corrupt depositaries of acaderr'cal pa-
tronage are a self-eleci ive body of professors.— H.

t Not St Francis, but St Antony (of Padua.)— H.

don't know what pleasure he had in his
audience ; but I should have none in mine
if there was not in it a mixture of reason-
able creatures. I confess I think there is
a smaller proportion of these in my class
this year than was the last, although the
number of the whole is not less. I have
long been of the opinion, that, in a right con-
stituted college, there ought to be two Pro-
fessors for each class — one for the dunces,
and another for those who have parts.
The province of the former would not be
the most agreeable, but, perhaps, it would
require the greatest talents, and, therefore,
ought to be accounted the post of honour.
There is no part of my time more disagree-
ably spent than that which is spent in
College meetings, of which we have often
five or six in a week. And I should have
been attending one this moment if a bad
cold I have got had not furnished me with
an excuse. These meetings are become
more disagreeable by an evil spirit of party
that seems to put us in a ferment, and, I
am afraid, will produce bad consequences.

The temper of our northern colonies
makes our mercantile people here look very
grave. Several of them are going to Lon-
don about this matter, to attend the pro-
ceedings of Parliament. It is said that the
effects in those colonies belonging to this
town amount to above £400,000 sterling.
The mercantile people are for suspending
the stamp-act, and redressing the grievances
of the colonists. Others consider their
conduct as an open rebellion, and an avowed
claim to independence, which ought to be
checked in the beginning. They say that,
for all their boasting, the colonists are a das-
tardly, pusillanimous race, and that a Bri-
tish fleet and army would soon reduce them
to such terms as would secure their future
dependence upon the mother country; that
this is the most proper time for doing so
when we are at peace with all our neigh-
bours. In what light the House of Com-
mons will view this matter, I don't know,
but it seems to be one of the most import-
ant matters that have come before them.
I wish often an evening with you, such as
we have enjoyed in the days of former
times, to settle the important affairs of
State and Church, of Colleges and Corpora-
tions. I have found this the best expedient
to enable me to think of them without
melancholy and chagrin. And I think all
that a man has to do in the world is to
keep his temper and to do his duty.
Mrs Reid is tolerably well just now, but is
often ailing. She desires to be remembered
to you and all your family.— I am, dear Sir,
Yours most affectionately,
Thomas Reid.

Glasgou. Dec. 30, 1765.





Glasgow, 23 March 1766.
Dear Sib,— I had yours of the 14th,
and this moment that of Thursday the 20,
with the inclosed, a letter from your papa
by Mr Duguid, with your circular thermo-
meter. I returned the thermometer, re-
paired by Mr Annan, who left this two days
ago, but was to be a week at Edinburgh in
his return. I shall remember Sir Archi-
bald Grant's commission, but must take
some time to think of it. What would you
think of Alex. Mearns in Gordon's Hospi-
tal ? If you are not acquainted with him,
you may learn his qualities, and tell me
your sentiments. I shall likewise mind your
ell 'ptical thermometer. Mr Stewart's* death
affects me deeply. A sincere friendship,
begun at twelve years of age, and continued
to my time of life without any interruption,
cannot but give you some pangs. You
know his worth, yet it was shaded ever
since you knew him by too great abstraction
from the world- The former part of his life
was more amiable and more social, but the
whole was of a piece in virtue, candour, and
humanity. I have often regretted that the
sol icitude of pro viding for a numerous family,
and the labour of managing an estate and a
farm, should make a man in a great measure
unknown, whose virtue, integrity, and judg-
ment ought to have shone in a more exten-
sive sphere. His scholars could not but
observe and revere his virtues ; and I have
no doubt but great numbers of them have
reapedgreat improvement by him in matters
of higher importance than mathematical
knowledge. I have always regarded him as
my best tutor, though of the same age with
me. ■ If the giddy part of my life was in any
degree spent innocently and virtuously, I
owe it to him more than to any human
creature ; for I could not but be virtuous in
his company, and I could not be so happy
in any other. But I must leave this pleas-
ing melancholy subject. He is happy; and
I shall often be happy in the remembrance
of our friendship ; and I hope we shall meet

There is no such thing as chymical fur-
naces made here for sale. They are made
of plate iron : and a white-iron-man manages
that materia 1 better than a blacksmith. But
you must direct them in everything, and be
still over the work.

I can give but an imperfect account of

* John Stuart, Professor of Mathematics in
Marischal College. This chair is in the presentation
of the Town Council of Aberdeen j and on the va.
cancy, by Stuart's death, Dr Hcid was appointed one
of the examinators of c.imlidatc, for the oificc — H.

the doctrine of latent heat ; but some hint
I shall give, trusting entirely to your hououi
that you will be cautious not to make any
use of it that may endanger the discoverer
being defrauded of his property.

There is in every body a certain quantity
of heat, which makes a part of its form or
constitution, and which it never parts with
without losing or changing its form. This is
called the latent heat of that body. All or
most bodies hare three different forms —
hardness, fluidity, and steam or vapour.
Take water, for an example, in its hard state,
that of ice : we have no means of knowing
what latent heat it may contain ; hut in its
fluid state it has about 140° of latent heat
more than it had in the state of ice. This
heat is latent while the water is fluid ; it
does not affect the thermometer, nor pro-
duce any other effect but that of making the
body fluid. In the very act of melting from
the state of ice to that of water, 140° of heat
is absorbed from the circumambient bodies
without making the water sensibly warmer
than the ice ; and in the act of passing from
the state of water to that of ice, 140° of heat
which was latent in the water becomes sen-
sible, and must pass from the water to the
ambient bodies before it can wholly be con-
verted into ice. As there is no intermediate
state between water and ice, a very small part
of the water freezes at once ; and the latent
heat of that part being communicated to the
remaining water, the freezing even in the
coldest air goes on piecemeal,' according as
the latent heat goes off first into the water
not yet frozen, and from that into the air or
ambient bodies.

Spermaceti, in passing from a solid to a
perfectly fluid form, requires about 150°
of heat, which becomes latent ; bees' wax
about 160°. But there is this remarkable
difference between these bodies — as well as
iron and some other metals on the one
hand, and water on the other — that the
former soften by degrees, so that there are
many intermediate degrees of softness be-
tween the hardest state which the body
takes by cold, and the state of perfect
fluidity ; whereas in water there seems to
be no intermediate degree between perfect
ice and perfect water. Accordingly, in
spermaceti, bees' wax, and iron, the latent
heat is more or less, according to the de-
gree of softness ; but in water it is always
the same. As water has about 140° of
latent heat more than ice, so steam has
about 800° of latent heat more than water ;
hence, an ounce of steam, though it have
little more sensible heat than boyling water,
will heat the cold water that condenses it
almost as much as four ounces of boyling
water would do. I can only at present
give you an experiment or two of the many
by which this theory is confirmed. But



first, it is proper to observe, that equal
quantities of the same fluid of different
temperatures, being mixed, the tempera-
ture of the mixed fluid is always an arith-
metical mean between the temperatures of
the ingredients. Thus, if a pound of water
of 40° be mixed with a pound of 100", the
mixed is found precisely 60°. This has been
tried in an infinite variety of cases, and
found to hold invariably, proper allowance
being made for the heat communicated to
the vessels, or drawn from them in the

Experiment 1. — Two Florence flasks had
six ounces of water put into each. In one
it was made to freeze ; in the other brought
as near as possible to the freezing point
without freezing — that is, to about 33°.
Both were set to warm in a large warm
room. The unfrozen water soon came to
the temperature of the room ; but the frozen
water took eleven or twelve hours to dis-
solve, and for the greatest part of that time
was not sensibly heated. A calculation
was made upon the supposition that the
frozen water had as much heat communi-
cated to it every half hour as the unfrozen
water had the first half hour. The result
of this calculation was, that the frozen
water had absorbed 136° or 140° of heat in
melting, over and above that which affected
the thermometer.

Exp. 2. — Six ounces of ice of the tem-
perature of 32° had six ounces of boyling
water poured upon it. The ice melted im-
mediately, and the whole water was 52"

Exp. 3. — From Mussehenbroek, with a
little variation. When the air is ten degrees
below the freezing point, set a deep, narrow
beer-glass of water to freeze, and let it re-
main perfectly at rest, without the least
motion. The water will cool regularly
below 32° without freezing, even to 22° ;
but, as soon as it is disturbed, a number of
icy spicuke are formed ; and in the same
moment the sensible heat rises to 32°, and
continues so till all is frozen.

I need not tell you, that by sensible heat
is meant that which diffuses itself to the
ambient bodies till all are brought to an
equilibrium. Of this the thermometer is
the measure. But latent heat adheres to
the body without any tendency to diffuse
itself to other bodies, unless they are able
to change the foim of the body from vapour
to a fluid, or from a fluid to ice or hardness —
then the latent heat goes off to other bodies,
and becomes sensible. I hope you will un-
derstand me, though I have wrote in a great
hurry. Yet I cannot find that Cullen or
the Edinburgh people know anything of this
matter. I may give you more of the ex-
periments afterwards.

Thomas Reid.



Glusiiaw, \8th April [17G6.]
Dear Sir, — There is like to be a vacancy
in one of the medical professions of this col-
lege, by the removal of Joseph Black to
Edinburgh. I thought, when I heard of
D^Whlte's (death, that there was very little
probability of our losing Dr Black by that
event ; because the Chymical Profession in
Edinburgh was that which was thought
fittest for l>r Black ; and there was good
reason to think that Cullen would not give
up the Chemistry for the Theory of Medi-
cine — though he would very willingly, ex-
change it for the Practice of Medicine.
But I was informed late yesternight, that
Dr Black is willing to accept of the Theory
of Medicine in Edinburgh, and that the
Council are certainly to present him. I
am very dubious whether his place here
would be worth your acceptance ; but I am
sure it would be so much the interest of
this society to have such a man in it, (and
I need not say how agreeable it would be
to me,) that I beg leave to inform you of
what 1 know of the state of the matter,
that you may think of it, and let me know
your thoughts. The salary of Dr Black's
place, is £50 as Professor of the Theory and
Practice of Medicine ; and the presentation
is in the Crown. The recommendation of the
College would probably have great weight,
if unanimous ; but I think there is no pro-
bability of an unanimous recommendation ;
so that the Court interest must probably
determine it. Dr Black, and Dr Cullen be-
fore him, had £20 yearly from the College, for
teaching chemistry ; and the College have,
from time to time, allowed, I believe, above
£500 for a laboratory. The chemical class
this session might bring £50 or £60 of fees,
and the medical class from £20 to £30 ; so
that the whole salary andfees will be between
£140 and £160. At the same time, the
College can at any time withdraw the £20,
and give that and the chemical laboratory to
another ; and it is not improbable that this
may be done if one be presented of whose
abilities in chemistry the College is not
satisfied. Dr Black, of late, had got a
great deal of practice in the medical way,
so as to leave him but little time for prose-
cuting his chemical discourses, and I think
you might expect the same after some time ;
for he had no natural connection here : it
was his merit alone that brought him into
it ; and he long resisted, instead of courting
it ; so that it was in a manner forced upon
him. The other medical Professor has
anatomy and botany for his province ; he
has a good anatomical class ; but ho Joes



not teach botany at all, nor is, as I appre-
hend, qualified to teach it. All I have far-
ther to say is, that there is a great spirit of
inquiry here among the young people. Lite-
rary merit is much regarded ; and I con-
ceive the opportunities a man has of improv-
ing himself are much greater than at Aber-
deen. The communication with Edinburgh
is easy. One goes in the stage-coach to Edin-
burgh before dinner ; has all the afternoon
there ; and returns to dinner at Glasgow
next day : so that, if you have any ambition
to get into the College of Edinburgh, (which,
I think, you ought to have,) I conceive
Glasgow would be a good step. Now, sir,
if you incline this place, you must, without
delay, try your interest at Court, and get
the best recommendations you can to the
members of this College. The Principal and
Mr Clow are not engaged ; they are the
only persons to whom I have made known,
or intend to make known, my writing to you.
Lord Findlater's interest, I think, would
have weight with Trail and Williamson. I
am told of three candidates — Dr Stevenson,
in Glasgow; Dr Smith Carmichael, a young
doctor, presently at London ; and one Dr
Stork, who was educated here. Each of
these, I apprehend, has interest with some
of the members, and depend upon them ; so
that we will probably be divided, and, con-
sequently, our recommendation, if any is
given, will have little weight at Court. If,
after due deliberation, you think it not worth
your while to stir in this matter for yourself,
will you be so good as communicate the state
of the case to Dr George Skene ?" He is the

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 12 of 114)