63c}--on
which he writes in his diary, "found it was old." Besides another paper
in the _Messenger of Mathematics_, he reviewed "Whitney on Language,"
{163d} and wrote a "Defence of Jevons" which I have not been able to
trace. In 1875 he was at work on the "Flow of Pitch," on an
"Equipotential Tracer," on slide rules, and sent a paper on "Cousin
Marriages" to the Statistical Society. {164a} It is not my province to
deal with these papers; they are enumerated here as showing his activity
of mind and his varied interests,--features in his character which were
notable throughout life.

The most interesting entry in his diary for 1875 is a "Paper on
Equipotentials much approved by Sir W. Thomson." This is the first
notice of an association of primary importance in George's scientific
career. Then came his memoir, "On the influence of geological changes in
the earth's axis of rotation." Lord Kelvin was one of the referees
appointed by the Council of the Royal Society to report on this paper,
which was published in the _Philosophical Transactions_ in 1877.

In his diary, November 1878, George records, "Paper on tides ordered to
be printed." This refers to his work, "On the bodily tides of viscous
and semi-elastic spheroids, etc.," published in the _Phil. Trans._ in
1879. It was in regard to this paper that his father wrote to George on
October 29th, 1878: {164b}

My dear old George,

I have been quite delighted with your letter and read it all with
eagerness. You were very good to write it. All of us are delighted,
for considering what a man Sir William Thomson is, it is most grand
that you should have staggered him so quickly, and that he should
speak of your 'discovery, etc.' . . . Hurrah for the bowels of the
earth and their viscosity, and for the moon and for the Heavenly
bodies, and for my son George (F.R.S. very soon). . . . {165a}

The bond of pupil and master between George Darwin and Lord Kelvin,
originating in the years 1877-8, was to be a permanent one, and
developed, not merely into scientific co-operation, but into a close
friendship. Sir Joseph Larmor has recorded {165b} that George's "tribute
to Lord Kelvin, to whom he dedicated Volume I of his Collected Papers
{165c} . . . gave lively pleasure to his master and colleague." His
words were:

Early in my scientific career it was my good fortune to be brought
into close personal relationship with Lord Kel