arch 10th, 1866 ("Life of Sir
Charles Lyell," II., page 408), in which the writer says that he is
"more than ever convinced that geographical changes...are the principal
and not the subsidiary causes.") I have come to this conclusion from
reflecting on the geographical distribution of the inhabitants of the
sea on the opposite sides of our continents and of the inhabitants of
the continents themselves.

LETTER 507. TO C. LYELL. Down, September 8th [1866].

Many thanks for the pamphlet, which was returned this morning. I was
very glad to read it, though chiefly as a psychological curiosity. I
quite follow you in thinking Agassiz glacier-mad. (507/1. Agassiz's
pamphlet, ("Geology of the Amazons") is referred to by Lyell in a letter
written to Bunbury in September, 1866 ("Life of Sir Charles Lyell," II.,
page 409): "Agassiz has written an interesting paper on the 'Geology of
the Amazons,' but, I regret to say, he has gone wild about glaciers, and
has actually announced his opinion that the whole of the great valley,
down to its mouth in latitude 0 deg., was filled by ice..." Agassiz
published a paper, "Observations Geologiques faites dans la Vallee de
l'Amazone," in the "Comptes Rendus," Volume LXIV., page 1269, 1867. See
also a letter addressed to M. Marcou, published in the "Bull. Soc. Geol.
France," Volume XXIV., page 109, 1866.) His evidence reduces itself to
supposed moraines, which would be difficult to trace in a forest-clad
country; and with respect to boulders, these are not said to be angular,
and their source cannot be known in a country so imperfectly explored.
When I was at Rio, I was continually astonished at the depth (sometimes
100 feet) to which the granitic rocks were decomposed in situ, and this
soft matter would easily give rise to great alluvial accumulations; I
well remember finding it difficult to draw a line between the alluvial
matter and the softened rock in situ. What a splendid imagination
Agassiz has, and how energetic he is! What capital work he would have
done, if he had sucked in your "Principles" with his mother's milk. It
is wonderful that he should have written such wild nonsense about the
valley of the Amazon; yet not so wonderful when one remembers that he
once maintained before the British Association that the chalk was all
deposited at once.

With respect to the insects of Chili, I knew only from Bates that the
species of Carabus showed no special affinity to northern species;
fr