vated, so that at that time the sources of the streams flowing in either direction must have been at least 100 feet above their present level, and 80 feet above the gravels at Brandon Down, and probably at some distance apart. That the heads of the two streams should have cut back their valleys, and at last have met, appears to be due to the fact that, previously to the covering of Boulder Clay being deposited, there existed an old depression in the Chalk, which had been filled with laminated sandy clays, either Glacial or belonging to what is known by geologists as the Chillesford series. These being more easily acted on than the chalk by running water, led the streams to follow the course of the old depression which they filled, and it is to their presence that the small inclination of the upper part of the valley of the Waveney appears to be mainly due. Another cause is to be found in the country near Lopham Ford being coated with clay, so that the streams, even at the present day, exhibit the remarkable phenomenon of being liable to floods at their source. An isolated hill, about 30 feet high, formed of the laminated beds, and with a slight capping of gravel, still remains in the valley of the Waveney, near Redgrave, to show the nature of the beds which have been removed.
The only spot in the valley of the Waveney, where as yet Palæolithic implements have been found, is at Hoxne, where the summit of the beds is about 111 feet above high-water mark at Yarmouth, and though at a higher level than the existing source of the Waveney, probably much below the level of its earlier source. Since the beds were deposited, the surface of the ground in the neighbourhood has been completely remodelled by sub-aërial denudation, and they now lie in a trough on the summit of a hill,[1] both sides of which slope down to small streams which are tributary to the Waveney, and are still at work cutting out their valleys in the Boulder Clay. The beds in which the implement occur are beyond all doubt of freshwater origin, being full of freshwater shells. The trough in which they lie, has much the appearance of the deserted bed of a river, silted up under more lacustrine conditions. Such a change in the position of a river-bed, and its subsequent infilling, is quite in accordance with the hypothetical case of river-action, especially when, as here, its eventual valley had not been distinctly carved out.
The phenomena at Hoxne have lately been more fully examined
- ↑ Prestwich, Phil. Trans., 1860, pl. xi. See p. 577, supra.
