which it is composed is one of its chief characteristic features; and
this may be well observed in any gravelly country, where a
recently-ploughed field immediately adjoins one which has long remained
undisturbed for pasture, and where the vegetable mould is exposed on the
sides of a ditch or hole. The subject may appear an insignificant one,
but we shall see that it possesses some interest; and the maxim de
minimis non curat lex, does not apply to science. Even Elie de
Beaumont, who generally undervalues small agencies and their accumulated
effects, remarks: {2} La couche tres-mince de la terre vegetale est un
monument d une haute antiquite, et, par le fait de sa permanence, un
objet digne d occuper le geologue, et capable de lui fournir des
remarques interessantes. Although the superficial layer of vegetable
mould as a whole no doubt is of the highest antiquity, yet in regard to
its permanence, we shall hereafter see reason to believe that its
component particles are in most cases removed at not a very slow rate,
and are replaced by others due to the disintegration of the underlying
materials.
As I was led to keep in my study during many months worms in pots filled
with earth, I became interested in them, and wished to learn how far they
acted consciously, and how much mental power they displayed. I was the
more desirous to learn something on this head, as few observations of
this kind have been made, as far as I know, on animals so low in the
scale of organization and so poorly provided with sense-organs, as are
earth-worms.
In the year 1837, a short paper was read by me before the Geological
Society of London, {3} On the Formation of Mould, in which it was shown
that small fragments of burnt marl, cinders, &c., which had been thickly
strewed over the surface of several meadows, were found after a few years
lying at the depth of some inches beneath the turf, but still forming a
layer. This apparent sinking of superficial bodies is due, as was first
suggested to me by Mr. Wedgwood of Maer Hall in Staffordshire, to the
large quantity of fine earth continually brought up to the surface by
worms in the form of castings. These castings are sooner or later spread
out and cover up any object left on the surface. I was thus led to
conclude that all the vegetable mould over the whole country has passed
many times through, and will again pass many times through, the
intestinal canals of worms. Hence the term animal mould would be in
some respects more appropriate than that commonly used of vegetable
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