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 EARLY MAN which we have seen was clearly after the deposit of the gravels at Warren Hill and other parts of the ridge, the ridge was continuous towards the east with the high ground which extends to and beyond Elveden about 5 miles away. The western boundary of the valley in which these ridge gravels were deposited had already disappeared in the general denudation which gave rise to the present fen districts and the surrounding low-lying chalky plain. On the slope resulting from this denudation Mousterian man lived and made his implements, which were successively buried in the brick-earth in which they are now found. When at some subsequent period the diluvial conditions arose which gave rise to the present river-system of this part of the country, great floods of water poured over from the higher ground in the neighbour- hood of Elveden and rushed down over the ridge (not yet separated on its eastern side) and so into the low-lying country beyond. The great main drain of the district was meantime forming, and is now represented by the River Lark. This would tend to draw towards itself the minor drains of the system, and amongst these would be that represented by the valley which has cut the ridge off from the high ground to the east. This valley would, however, not be formed all at once. It would be shorter and narrower, to begin with, than it subsequently became. But as it cut its way back north- wards it would tap first one and then another of the streams which up till then had been rushing from the high ground to the east towards and over the gravel-topped land which now constitutes our ridge. These streams flowing from east to west would in ordinary course be cutting their way down through the gravels and underlying strata, and with time would deepen and widen their beds. The tapping process described would deflect the water first of the ' gully,' then of the ' vale,' and finally of the ' valley,' The ' gully,' as we have seen, had attained a bottom width of 100 yds., when its further progress was thus stopped ; the ' vale ' a width of about a third of a mile, when it ceased to carry further water ; whilst the ' valley ' was a mile wide before it was finally tapped. Here, then, we must look for the explanation of the superposition of ' drift ' gravels to ' Mousterian ' brick-earth. Not only were there these three breaches made in the ridge by the rush of waters from the east, but a fourth breach was begun half-way between our ' gully ' and the Lark. The water had time to push the gravels capping the ridge at this point over on to the side of the ridge to the west, when the valley which the waters were excavating to the east of the ridge tapped the source of this flow, and here the gravels have remained to this day. The paradox in prehistoric archaeology thus caused comes as an aid to geology in clearing up a very curious problem. A comparatively simple confirmation of the account here given may be obtained. If it be the case that large portions of the ridge with its imple- mentiferous gravels have been carried away by the Lark and by the streams that gave rise to the breaches here described, then there ought to be some signs of the resulting debris in the valley of the Lark below the ridge and in the country to the west of the ridge ; and such evidence is forthcoming. A certain number of typical Warren Hill implements have been found at or near the surface of the ground at various spots in the lower Lark Valley ; and implements of pure ' drift ' types, and with typical ' drift ' patination, have been picked up on fields opposite each of the breaches described at 245