Life and Letters of Charles Darwin — Volume 2Darwin, Charles
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Life and Letters of Charles Darwin — Volume 2
Darwin, Charles
Darwin, Charles, 1809-1882; Naturalists -- Great Britain -- Biography; Naturalists -- Great Britain -- Correspondence
I am now going to mention a small observation, made by me two or three
years ago, near Southampton, but not followed out, as I have no strength
for excursions. I need say nothing about the character of the drift
there (which includes palaeolithic celts), for you have described its
essential features in a few words at page 506. It covers the whole
country [in an] even plain-like surface, almost irrespective of the
present outline of the land.
The coarse stratification has sometimes been disturbed. I find that you
allude "to the larger stones often standing on end;" and this is the
point which struck me so much. Not only moderately sized angular stones,
but small oval pebbles often stand vertically up, in a manner which I
have never seen in ordinary gravel beds. This fact reminded me of what
occurs near my home, in the stiff red clay, full of unworn flints over
the chalk, which is no doubt the residue left undissolved by rain
water. In this clay, flints as long and thin as my arm often stand
perpendicularly up; and I have been told by the tank-diggers that it
is their "natural position!" I presume that this position may safely be
attributed to the differential movement of parts of the red clay as it
subsided very slowly from the dissolution of the underlying chalk; so
that the flints arrange themselves in the lines of least resistance. The
similar but less strongly marked arrangement of the stones in the
drift near Southampton makes me suspect that it also must have
slowly subsided; and the notion has crossed my mind that during the
commencement and height of the glacial period great beds of frozen snow
accumulated over the south of England, and that, during the summer,
gravel and stones were washed from the higher land over its surface, and
in superficial channels. The larger streams may have cut right through
the frozen snow, and deposited gravel in lines at the bottom. But on
each succeeding autumn, when the running water failed, I imagine that
the lines of drainage would have been filled up by blown snow afterwards
congealed, and that, owing to great surface accumulations of snow, it
would be a mere chance whether the drainage, together with gravel and
sand, would follow the same lines during the next summer. Thus, as I
apprehend, alternate layers of frozen snow and drift, in sheets and
lines, would ultimately have covered the country to a great thickness,
with lines of drift probably deposited in various directions at the
bottom by the larger streams. As the climate became warmer, the lower
beds of frozen snow would have melted with extreme slowness, and the
many irregular beds of interstratified drift would have sunk down with
equal slowness; and during this movement the elongated pebbles would
have arranged themselves more or less vertically. The drift would also
have been deposited almost irrespective of the outline of the underlying
land. When I viewed the country I could not persuade myself that any
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