lopes,
with Remarks on the Mode of Origin of Mount Etna and on the Theory of
'Craters of Elevation,'" by C. Lyell, "Phil. Trans. R. Soc." Volume
CXLVIII., page 703, 1859.) It seems to me a very grand contribution to
our volcanic knowledge. Certainly I never expected to see E. de B.'s
[Elie de Beaumont] theory of slopes so completely upset. He must have
picked out favourable cases for measurement. And such an array of facts
he gives! You have scotched, and will see die, I now think, the Crater
of Elevation theory. But what vitality there is in a plausible theory!
(490/2. The rest of this letter is published in "Life and Letters," II.,
page 129.)

LETTER 491. TO C. LYELL. Down, November 25th [1860].

I have endeavoured to think over your discussion, but not with much
success. You will have to lay down, I think, very clearly, what
foundation you argue from--four parts (which seems to me exceedingly
moderate on your part) of Europe being now at rest, with one part
undergoing movement. How it is, that from this you can argue that the
one part which is now moving will have rested since the commencement of
the Glacial period in the proportion of four to one, I do not pretend
to see with any clearness; but does not your argument rest on the
assumption that within a given period, say two or three million years,
the whole of Europe necessarily has to undergo movement? This may
be probable or not so, but it seems to me that you must explain the
foundation of your argument from space to time, which at first, to me
was very far from obvious. I can, of course, see that if you can make
out your argument satisfactorily to yourself and others it would be most
valuable. I can imagine some one saying that it is not fair to argue
that the great plains of Europe and the mountainous districts of
Scotland and Wales have been at all subjected to the same laws of
movement. Looking to the whole world, it has been my opinion, from the
very size of the continents and oceans, and especially from the enormous
ranges of so many mountain-chains (resulting from cracks which follow
from vast areas of elevation, as Hopkins argues (491/1. See "Report
on the Geological Theories of Elevation and Earthquakes." by William
Hopkins. "Brit. Assoc. Rep." 1847, pages 33-92; also the Anniversary
Address to the Geological Society by W. Hopkins in 1852 ("Quart. Journ.
Geol. Soc." Volume VIII.); in this Address, pages lxviii et seq.)
reference is made to the theor