the original patents, the references to old fields are very numerous; these were lands which, after passing out of cultivation, had at first been given up as pastures to roaming cattle, but which in a few years relapsed into thickets, and finally into forests of a second growth. There was an abundance of natural manures which might have been scattered over the surface of these impoverished fields if their owners had considered it to be advisable. Rolfe had observed the presence of marl in the Powhatan valley, and drawn attention to its value as a means of increasing the fertility of ground under tillage.[1] Clayton, who visited the Colony in 1688, was very much impressed by the spectacle of the vast quantity of shells, which, with little trouble, could be converted into lime; in some places, he came upon deposits extending for several miles, the soil being so much intermixed with oyster shells that it seemed to be composed more of shells than of earth. At the foot of many hills where the underground was exposed to view, he saw veins of shell rock three or four yards in thickness, and in many cases pieces of this rock which had fallen off were several tons in weight. As the soil was thin and sandy, Clayton was of the opinion that marl and not lime should be used in manuring it.[2]
It was not until nearly a century and a half had passed that the value of these natural manures was generally recognized. It is recorded that Governor Yeardley used marl on one occasion to increase the fertility of a small tract which he had under tillage; but the example that be set was not followed on a notable scale until Edmund Ruffin, in his memorable treatise on calcareous manures, pointed out the important part which this material could
