In places the land is too steep or too elevated to be cultivated, and so it is left as pasture for the sheep or "sheep walk"; where cultivation is possible the fields are large and without hedges, like those shown in Fig. 51; during autumn, winter and spring there are many sheep about, penned or "folded" on the arable land, eating the crops of swedes, turnips, rape, vetches or mustard grown for them, or grazing on the aftermath of sainfoin or grass and clover. So important are sheep in chalk districts that the whole scheme of farming is often based on their requirements, but corn is also a valuable crop, and, especially in dry districts, barley, so that chalk soils are often spoken of as "sheep and barley" soils. Although the pastures are very healthy there is not generally much food or "keep" for the animals during the summer because of the dryness. [Illustration: Fig. 51. Open chalk cultivated country, Isle of Thanet] The black soil of the fen districts and elsewhere is widely different from any of the preceding. It contains, as its colour shows, a large quantity of combustible material (Chap. V.), which has a great power of holding water. These fens are therefore very wet; until they were drained they were desolate wastes: you may {114} read in Kingsley's _Hereward the Wake_ what they used to be like in old days, and even as late as 1662 Dugdale writes that here "no element is good. The air cloudy, gross and full of rotten harrs[1]; water putrid and muddy, yea, full of loathsome vermin; the earth spongy and boggy; and the fire noisome by the stink of smoking hassocks[2]." But during the Stuart period wide ditches or drains were dug, into which the water could flow and be pumped into rivers. This reclamation has been continued to the present time, and the black soils as well as the others in the Fen districts can be made very productive.