[For many years after this his favourite mode of recruiting from the
results of a spell of overwork was to take a short walking tour with a
friend. In April 1857 he is off for a week to Cromer; in 1860 he goes
with Busk and Hooker for Christmas week to Snowdon; another time he is
manoeuvred off by his wife and friends to Switzerland with Tyndall.

In Switzerland he spent his summer holidays both in 1856 and 1857, in
the latter year examining the glaciers with Tyndall scientifically, as
well as seeking pleasure by the ascent of Mont Blanc. As fruits of this
excursion were published late in the same year, his "Letter to Mr.
Tyndall on the Structure of Glacier Ice" ("Phil. Mag." 14 1857), and the
paper in the "Philosophical Transactions of the Royal Society," which
appeared--much against his will--in the joint names of himself and
Tyndall. Of these he wrote in 1893 in answer to an inquiry on the
subject:--]

By the Observations on Glaciers I imagine you refer to a short paper
published in "Phil. Mag." that embodied results of a little bit of work
of my own. The Glacier paper in the "Phil. Trans." is essentially and in
all respects Professor Tyndall's. He took up glacier work in consequence
of a conversation at my table, and we went out to Switzerland together,
and of course talked over the matter a good deal. However, except for my
friend's insistence, I should not have allowed my name to appear as
joint author, and I doubt whether I ought to have yielded. But he is a
masterful man and over-generous.

[And in a letter to Hooker he writes:--]

By the way, you really must not associate me with Tyndall and talk about