back
Agassiz sooner, but my servant has been very unwell. Emma is going on
pretty well.

My paper on South American boulders and "till," which latter deposit
is perfectly characterised in Tierra del Fuego, is progressing rapidly.
(499/6. "On the Distribution of the Erratic Boulders and on the
Contemporaneous Unstratified Deposits of South America," "Trans. Geol.
Soc." Volume VI., page 415, 1842.)

I much like the term post-Pliocene, and will use it in my present paper
several times.

P.S.--I should have thought that the most obvious objection to the
marine-beach theory for Glen Roy would be the limited extension of the
shelves. Though certainly this is not a valid one, after an intermediate
one, only half a mile in length, and nowhere else appearing, even in the
valley of Glen Roy itself, has been shown to exist.

LETTER 500. TO C. LYELL. 1842.

I had some talk with Murchison, who has been on a flying visit into
Wales, and he can see no traces of glaciers, but only of the trickling
of water and of the roots of the heath. It is enough to make
an extraneous man think Geology from beginning to end a work of
imagination, and not founded on observation. Lonsdale, I observe, pays
Buckland and myself the compliment of thinking Murchison not seeing as
worth nothing; but I confess I am astonished, so glaringly clear after
two or three days did the evidence appear to me. Have you seen last "New
Edin. Phil. Journ.", it is ice and glaciers almost from beginning to
end. (500/1. "The Edinburgh New Philosophical Journal," Volume XXXIII.
(April-October), 1842, contains papers by Sir G.S. Mackenzie, Prof.
H.G. Brown, Jean de Charpentier, Roderick Murchison, Louis Agassiz, all
dealing with glaciers or ice; also letters to the Editor relating to
Prof. Forbes' account of his recent observations on Glaciers, and a
paper by Charles Darwin entitled "Notes on the Effects produced by the
Ancient Glaciers of Carnarvonshire, and on the Boulders transported by
Floating Ice.") Agassiz says he saw (and has laid down) the two lowest
terraces of Glen Roy in the valley of the Spean, opposite mouth of Glen
Roy itself, where no one else has seen them. (500/2. "The Glacial Theory
and its Recent Progress," by Louis Agassiz, loc. cit., page 216. Agassiz
describes the parallel terraces on the flanks of Glen Roy and Glen Spean
(page 236), and expresses himself convinced "that the Glacial theory
alone satisfies all the exigencies of the phenomenon" of