To John Scott   15 January 1872

My Dear Sir,—

Many years ago I wrote a paper showing that stones laid on a grass field gradually become completely covered up by worm castings. I am now resuming the subject and making more accurate observations, as I believe they will bear on the denudation of the land.¹ You will remember the appearance of lawns, fields, and commons in England, especially during the autumn. Now I want much to know whether in India worms eject their castings on the surface in like manner.² A surface which is continually dug is not good for observation, but I suppose you could find some neglected part of the garden which you could observe. I find here abundant castings even in rather thick woods. If there are such castings, I should like to know whether they are numerous, and whether they are larger or smaller than those in England. If you could spare the time I should be very glad to hear how any two or three fresh castings marked by you disappeared. Does the heavy tropical rain wash them quickly away? The heavy rain in England causes a fresh casting to subside into a disk which will flow an inch or so down a slope. If they once get dry they endure for a surprising time, crumble into pellets, with part washed away and the remainder covered by growing grass. If these trifling observations would not trouble you, I should be really obliged. If you watch any fresh castings, you would have to enclose with stakes or somehow the spot, so that no one might trample them down.

My Dear Sir, yours very sincerely, | Ch. Darwin.

I wrote to you a month or two ago.³

N.B.—I have not yet been able to ascertain whether the castings on a sandy soil ever disintegrate into dust or powder, so that they can be blown away.

Have you ever observed how deep worms burrow in India?