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Show 294 DENUDA'riON OF TIIE LAND. CIIAP. VI. ou the crowns; but this would naturally follow from the finer earth having been washed from the crowns into the furrows before the land was well clothed with turf; and it is impossible to tell what part worm may have played in the work. Nevertheless frmn what wo have seen, castings would certainly tend to flow and to be washed during heavy rain from the crowns into the furrows. But as soon as a bed of fine earth had by any 1neans been accumulated in the furrows, it would be more favourable for worms than the other parts, and a greater number of castings \Vould be thrown up here than elsewhere; and as the furrows on sloping land are usually directed so as to carry off the surface water, son1e of tho finest earth would be washed frmn the castings which had been hero ejected and be carried completely away. The re ult would be that the furrows would be filled up very slowly, while the crowns would be lowered perhaps still more slowly by the flowing and rolling of the castings down their gentle iuclinations into the furrows. N evcrtheless it might be expected that old furrows, especially those on a sloping surface, Crru. VI. ANCIENTLY PLOUGHED FIELDS. 295 would in the course of time be filled np and disappear. Some careful observers, however, who examined fields for me in Gloucestershire and Staffordshire, could not detect any difference in the state of the furrows in the upper and lower parts of sloping fields, supposed to have been long in pasture; and they ca1ne to the conclusion that the crowns and furrows would last for an almost endless number of centuries. On the other hand the process of obliteration seems to have commenced in some places. Thus in a grass field in North Wales, known to have been ploughed about 65 years ago, which sloped at an angle of 15° to the noTth-east, the depth of the furrows (only 7 feet apaTt) was carefully measured, and was found to be al>out 4! inches in the upper part of the slope, and only l inch near the base, where they could be traced with difficulty. On another field sloping at about the same anglo to the southwest, the furrows were scarcely perceptible in the lower part ; although these same furrows when followed on to some adjoining level ground were from 2~- to 3~- inches in' depth. A third and closely similar case was |