Dear Marshall

It has just occurred to me that you might have an opportunity of observing a small fact for me, & which if I asked most persons to observe I sh^d. be thought to be a raving lunatic.— I want to know how deep down earth-worms make their tubular burrows.— Perhaps you w^d. have a chance when foundations are being dug, if you could remember to do so.—² An earth-worm cut into two pieces w^d be the best evidence, but the burrows can be recognized by being generally lined with fine black earth.— It w^d be easy to measure how many feet beneath the surface such burrows c^d. be seen.—³

Where a house has long stood the ground beneath w^d. of course be too dry for worms, but I especially want to know, whether the earth is damp enough through capillary attraction, beneath any projection, some 8 or 10 feet across, for earth-worms to live & burrow. It is just possible you might have some opportunity of observing this. It is too long a story for me to explain why I am interested about the habits of worms.—

If you can help me, I am sure that you will.— Believe me, yours sincerely | Ch. Darwin