PROFESSOR AT KING’S COLLEGE, LONDON.--LIFE AT GLENLAIR.
In 1860 Forbes resigned the chair of Natural Philosophy at Edinburgh.
Maxwell and Tait were candidates, and Tait was appointed. In the
summer of the same year Maxwell obtained the vacant Professorship of
Natural Philosophy at King’s College, London. This he held to 1865,
and this period of his life is distinguished by the appearance of
some of his most important papers. The work was arduous; the College
course extended over nine months of the year; there were as well
evening lectures to artisans as part of his regular duties. His life in
London was useful to him in the opportunities it gave him for becoming
personally acquainted with Faraday and others. He also renewed his
intimacy with various Cambridge friends.
He was at the celebrated Oxford meeting of the British Association in
1860, where he exhibited his colour-box for mixing the colours of the
spectrum. In 1859, at the meeting at Aberdeen, he had read to Section
A his first paper on the “Dynamical Theory of Gases,” published in the
_Philosophical Magazine_ for January, 1860. The second part of the
paper, dealing with the conduction of heat and other phenomena in a
gas, was published in July, 1860, after the Oxford meeting.
A paper on the “Theory of Compound Colours” was communicated to
the Royal Society by Professor Stokes in January, 1860. It contains
the account of his colour-box in the form finally adopted (most of
the important parts of the apparatus are still at the Cavendish
Laboratory), and a number of observations by Mrs. Maxwell and himself,
which will be more fully described later.
In November, 1860, he received for this work the Rumford medal of the
Royal Society.
The next year, 1861, is of great importance in the history of
electrical science. The British Association met at Manchester, and a
Committee was appointed on Standards of Electrical Resistance. Maxwell
was not a member. The committee reported at the Cambridge meeting in
1862, and were reappointed with extended duties. Maxwell’s name, among
others, was added, and he took a prominent part in the deliberations
of the committee, which, as their Report[30] presented in 1863 states,
came to the opinion, “after mature consideration, that the system
of so-called absolute electrical units, based on purely mechanical
measurements, is not only the best system yet proposed, but is the
only one consistent with our present knowledge both of the relations
existing between the various electrical phenomena and of the connection
between these and the fundamental measurements of time, space, and
mass.”
Appendix C of this Report, “On the Elementary Relations between
Electrical Measurements,” bears the names of Clerk Maxwell and Fleeming
Jenkin, and is the foundation of everything that has been done in the
way of absolute electrical measurement since that date; while Appendix
D gives an account by the same two workers of the experiments on the
absolute unit of electrical resistance made in the laboratory of King’s
College by Maxwell, Fleeming Jenkin, and Balfour Stewart. Further
experiments are described in the report for 1864. The work thus begun
was consummated during the year 1894 by the legalisation throughout
the civilised world of a system of electrical units based on those
described in these reports.
Meanwhile, Maxwell’s views on electro-magnetic theory were quietly
developing. Papers on “Physical Lines of Force,” which appeared in the
_Philosophical Magazine_ during 1861 and 1862, contain the germs of
his theory--expressed at that time, it is true, in a somewhat material
form. In the paper published January, 1862, the now well-known relation
between the ratio of the electric units and the velocity of light was
established, and his correspondence with Fleeming Jenkin and C. J.
Munro about this time relates in part to the experimental verification
of this relation. His experiments on this matter were published in the
“Philosophical Transactions” for 1868.
This electrical theory occupied his mind mainly during 1863 and 1864.
In September of the latter year he writes[31] from Glenlair to C.
Hockin, who had taken Balfour Stewart’s place during the second series
of experiments on the measurement of resistance.
“I have been doing several electrical problems. I have got a
theory of ‘electric absorption,’ _i.e._, residual charge, etc.,
and I very much want determinations of the specific induction,
electric resistance, and absorption of good dielectrics, such
as glass, shell-lac, gutta-percha, ebonite, sulphur, etc.
“I have also cleared the electromagnetic theory of light from
all unwarrantable assumption, so that we may safely determine
the velocity of light by measuring the attraction between
bodies kept at a given difference of potential, the value of
which is known in electromagnetic measure.
“I hope there will be resistance coils at the British
Association.”
This work resulted in his greatest electrical paper, “A Dynamical
Theory of the Electromagnetic Field,” read to the Royal Society
December 8th, 1864.
But the molecular theory of gases was still prominently before his mind.
In 1862, writing[32] to H. R. Droop, he says:--
“Some time ago, when investigating Bernoulli’s theory of gases,
I was surprised to find that the internal friction of a gas (if
it depends on the collision of particles) should be independent
of the density.
“Stokes has been examining Graham’s experiments on the rate
of flow of gases through fine tubes, and he finds that the
friction, if independent of density, accounts for Graham’s
results; but, if taken proportional to density, differs from
those results very much. This seems rather a curious result,
and an additional phenomenon, explained by the ‘collision of
particles’ theory of gases. Still one phenomenon goes against
that theory--the relation between specific heat at constant
pressure and at constant volume, which is in air = 1·408, while
it ought to be 1·333.”
And again[33] in the same year, 21st April, 1862, to Lewis Campbell:--
“Herr Clausius of Zürich, one of the heat philosophers, has
been working at the theory of gases being little bodies flying
about, and has found some cases in which he and I don’t tally.
So I am working it out again. Several experimental results have
turned up lately rather confirmatory than otherwise of that
theory.
“I hope you enjoy the absence of pupils. I find the division of
them into smaller classes is a great help to me and to them;
but the total oblivion of them for definite intervals is a
necessary condition for doing them justice at the proper time.”
The experiments on the viscosity of gases, which formed the Bakerian
Lecture to the Royal Society read on February 8th, 1866, were the
outcome of this work. His house in 8, Palace Gardens, Kensington,
contained a large garret running the complete length.
“To maintain the proper temperature a large fire was for some days kept
up in the room in the midst of very hot weather. Kettles were kept on
the fire and large quantities of steam allowed to flow into the room.
Mrs. Maxwell acted as stoker, which was very exhausting work when
maintained for several consecutive hours. After this the room was kept
cool for subsequent experiments by the employment of a considerable
amount of ice.”
Next year, May, 1866, was read his paper on the “Dynamical Theory of
Gases,” in which errors in his former papers, which had been pointed
out by Clausius, were corrected.
Meanwhile he had resigned his London Professorship at the end of the
Session of 1865, and had been succeeded by Professor W. G. Adams.
For the next four years he lived chiefly at Glenlair, working at his
theory of electricity, occasionally, as we shall see, visiting London
and Cambridge, and taking an active interest in the affairs of his
own neighbourhood. In 1865 he had a serious illness, through which he
was nursed with great care by Mrs. Maxwell. His correspondence was
considerable, and absorbed much of his time. Much also was given to the
study of English literature; he was fond of reading Chaucer, Milton, or
Shakespeare aloud to Mrs. Maxwell.
He also read much theological and philosophical literature, and all he
read helped only to strengthen that firm faith in the fundamentals of
Christianity in which he lived and died.
In 1867 he and Mrs. Maxwell paid a visit to Italy, which was a source
of great pleasure to both.
His chief scientific work was the preparation of his “Electricity and
Magnetism,” which did not appear till 1873; the time was in the main
one of quiet thought and preparation for his next great task, the
foundation of the School of Physics in Cambridge.
In 1868 the principalship of the United College in the University of
St. Andrews was vacant by the resignation of Forbes, and Maxwell was
invited by several of the professors to stand. He, however, declined to
submit his name to the Crown.