1869]. WOOD INTRAGLACIAL EROSION. 259 



water lake called Breydon Water, which lies on the west of Yar- 

 mouth, 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 ] 004 Sweyn took his fleet up to N'orwich 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. 



Discussioisr. 



Mr. GwTis^ Jeffreys suggested a zoological as well as a geolo- 

 gical 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. Eamsat 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 Ehine 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., E.G.S., and E. W. Harmer, Esq. 



(The publication of this paper is deferred.) 

 [Abstract.] 



Tke 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 Norvrich 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 de- 

 posit of dark-blue clay, full of chalk debris, exactly resembling the 

 Boulder-clay at a distance from Norwich, but quite different in cha- 

 racter from that occurring in the vicinity (No. 5) ; and this is over- 

 lain 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 



