ition by a large river, and other such evidence. Your main argument
with respect to the sun seems to me very striking.

My son George desires me to thank you for his copy, and to say how much
he has been interested by it.

2.IX.VII. GEOLOGICAL ACTION OF EARTHWORMS, 1880-1882.

"My whole soul is absorbed with worms just at present." (From a letter
to Sir W. Thistleton-Dyer, November 26th, 1880.)

LETTER 547. TO T.H. FARRER (Lord Farrer).

(547/1. The five following letters, written shortly before and after the
publication of "The Formation of Vegetable Mould through the Action of
Worms," 1881, deal with questions connected with Mr. Darwin's work on
the habits and geological action of earthworms.)

Down, October 20th, 1880.

What a man you are to do thoroughly whatever you undertake to do! The
supply of specimens has been magnificent, and I have worked at them for
a day and a half. I find a very few well-rounded grains of brick in
the castings from over the gravel walk, and plenty over the hole in the
field, and over the Roman floor. (547/2. See "The Formation of Vegetable
Mould," 1881, pages 178 et seq. The Roman remains formed part of a villa
discovered at Abinger, Surrey. Excavations were carried out, under Lord
Farrer's direction, in a field adjoining the ground in which the Roman
villa was first found, and extended observations were made by Lord
Farrer, which led Mr. Darwin to conclude that a large part of the fine
vegetable mould covering the floor of the villa had been brought up
from below by worms.) You have done me the greatest possible service
by making me more cautious than I should otherwise have been--viz., by
sending me the rubbish from the road itself; in this rubbish I find
very many particles, rounded (I suppose) by having been crushed, angles
knocked off, and somewhat rolled about. But not a few of the particles
may have passed through the bodies of worms during the years since the
road was laid down. I still think that the fragments are ground in the
gizzards of worms, which always contain bits of stone; but I must try
and get more evidence. I have to-day started a pot with worms in very
fine soil, with sharp fragments of hard tiles laid on the surface, and
hope to see in the course of time whether any of those become rounded. I
do not think that more specimens from Abinger would aid me...

LETTER 548. TO G.J. ROMANES. Down, March 7th.

I was quite mistaken about the "Gardeners' Chronicl