From G. H. Darwin   30 December 1871

A grass field betw. Leaves Green & the Salt Box house on the right hand of the road is marked with ridge & furrow.¹ The field contains the end of a small valley where it quite dies out, so that the land is somewhat in the shape of a shallow spoon;—the furrows run parallel to the main line of the small valley ie parallel to the handle of the spoon.— Horace² & I attempted to find the depth of the soil above the flints in the steepest part where the furrows ran transversly to the hill by probing with a stick   I probed in the furrows & he on the ridges about 10 or 15 times each & then I found that the average distances of the flints below the surface on the furrows & ridges were about 5 inches & 3$\frac{1}{2}$ inches respectively. We excluded the cases in wh. the stick obviously missed the flints & went in deep.— We tried the same thing in a part of the field which was nearly flat & found the depth below the furrows & ridges to be about 4 inches & 3$\frac{1}{2}$ inches respectively.— The furrows appeared slightly more filled up on the hill side than on the flat   There were a good many earth castings about tho’ I sh^d. say that they were by no means very numerous

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