Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/355

 water lake called Breydon Water, which lies on the west of Yarmouth, and to which the tide still has access ; this at present receives the waters of the Bare, the Yare, and the Waveney.

The author considers that the submergence of these valleys may have persisted in part until the historic period ; for it is stated that in the year 1004 Sweyn took his fleet up to Norwich and burned that city ; and as late as the year 1347 Yarmouth stood upon an island, being separated from the mainland by a northern channel called " Grubb's Haven," which was subsequently silted up.

Discussion.

Mr. Gwyn Jeffreys suggested a zoological as well as a geological examination of these lakes. If of marine origin, possibly some marine forms might be found still existing in them, as had been discovered to be the case in some of the lakes of Sweden.

Mr. Searles Wood, Jun., agreed that these broads were of later date than the excavation of the valleys. He cited Mr. Prestwich's account of the boring at Yarmouth, which showed a large amount of silting up of the valley.

Mr. Prestwich inquired whether the amount of silt at the bottom of these broads had been ascertained, and whether any estuarine shells had been found in the beds at the bottom.

Prof. Ramsay suggested that the broads might be relics of the old valleys of the time when the Thames and other rivers of the east of England united with the Rhine and other continental rivers to flow into the Northern Ocean.

5. On a peculiar Instance of Intraglacial Erosion near Norwich. By Searles Wood, Jun., Esq., F.G.S., and F. W. Harmer, Esq.

(The publication of this paper is deferred.)

[Abstract.]

The authors described the general structure of the valley of the Yare, near Norwich, in which the fundamental chalk-rock is covered by the following drift-beds: — 1, the Chillesford sand and clay; 2, pebbly sands and pebble-beds ; 3, the equivalent of the contorted Drift of Cromer; 4, the middle glacial sand; and, 5, the Boulder-clay. The valley is hollowed out in these beds. Sewer-shafts sunk in the bottom of the valley near Norwich have shown the existence of an abrupt hole or narrow trough in the chalk, having one of its sides apparently almost perpendicular. This is filled up in part by a deposit of dark-blue clay, full of chalk debris, exactly resembling the Boulder-clay at a distance from Norwich, but quite different in character from that occurring in the vicinity (No. 5) ; and this is overlain in part by a bed of the middle glacial sand (No. 4), and in part by a postglacial gravel. The authors believed that this peculiar hole or trough was excavated by glacial action after the deposition of the bed No. 3, and that it belongs to the earliest part of the