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I have seen in N Wales, land showing by ridges and furrows that it had been ploughed apparently centuries ago. Do such exist in your neighbourhood, or can you find a field with ridges and furrows which has been laid down in grass for about 1/2 a century or more? In all such cases if the surface slopes, I want much to learn whether the ridges and furrows run straight or obliquely down the slope, or transversely across it. In the former case it would be of the greatest service to me if you would observe whether the ridges and furrows are as distinct near the base of the slope as at its top. By far the best way to observe wd. be to stretch a string in 2 or 3 places from ridge to ridge and measure the depths of the furrow in the upper and in the lower part of the slope. If the ridges and furrows runs transversely across the slope, the only point to observe would be whether the two slopes of the ridges have become different to what they are in a recent stubble field.— In any field observed please to notice whether there are many worm-castings about.—

My object is to trace the manner of gradual obliteration of ridge and furrow in old pasture-land, as far as such obliteration is ever effected.

C. Darwin