556 Fisher — Denudations of Norfolk. 



littoralis is also common, and Corbicula fluminalis in the lower parts of the valleys. 

 Worked flints do not appear to be usual (if, indeed, they occur at all) in the deposits 

 of this age. The occurrence of Elephas antiques in association with worked flints 

 appears by no means usual. ^ 



The valley deposits of Ilford, Grays, Clacton, Lexden, and Walton-on-the-Naze, 

 all in Essex, appear to be of this earlier age ; and at Clacton there is clear evi- 

 dence, and at Grays probable evidence, that a subsequent submergence occurred, 

 since the lower part of the deposit, in which the mammalian bones and land and 

 freshwater shells are found, is covered, in the one case by a distinctly estuarine de- 

 posit, and in the other by false bedded sands, which can scarcely be otherwise than 

 estuarine. 



I would refer the marine deposits of the valley of the Nar to the close of this 

 period,^ because they are newer than the Boulder-clay^ but older than the estuarine 

 mud (Scroblcularia clay) of the Fens,* which, as already mentioned, overlies the 

 submarine forest. But it must be admitted that the exact age of the Nar deposits 

 has not hitherto been determined. 



I am disposed to place the deposit at Mundesley among the earlier valley de- 

 posits, on account of the occurrence of Elephas antiqmis there. Mr. Gunn has the 

 specimen in his possession, which was obtained from the dark silt {b) of Mr. 

 Prestwich's section.^ 



The consideration of the present condition of the surface in connection with the 

 form of the ground and of the denuding agents has led me to refer to the order of 

 the later events in a reverse order. I will shortly recapitulate them in the order of 

 their occurrence. 



After marine denudation had removed vast quantities of deposits, probably 

 exposing the Chalk and the other strata in those areas which they now occupy, 

 the earliest valley denudation, of which we have records remaining, was that 

 characterised by the Elephas antiquus in company with priiiiigenius. This valley 

 system was partly submerged, and again re-elevated to an altitude greater than 

 the present. This second period was that of the Elephas prmiigeitms, with but 

 few of its former companion, antiqinis, and of the fabricators of the early chipped 

 implements. A subsequent denudation took place, of which the travelled material, 

 which I call trail, is the testimony. 



The warp covering the general surface was formed toward the latter part of this 

 period, and, as 1 conceive, the Reindeer then lived in our latitudes, and Elephas 

 primigenius still survived. This was the period also of the submarine forests which 

 occupy most of our low shores. A depression then occurred which covered the 

 lower forest grounds with the Scrobiculai-ia mud (called " buttery clay" in the Fens), 

 and I have found the warp of the lower grounds beneath it in Essex. ^ 



A final elevation of a few feet introduced the recent period. 



I have already alluded to the condition of the surface which shows traces of the 

 upper portion having been moved in a plastic state. I will now call your attentioi 

 to some features in the contour of the surface in this county which ought to thro^ 

 light on the mode of final denudation. 



In the first place the broads of Norfolk are a peculiar feature. They are portions ' 

 of the valleys which have not had time to become filled up, either by silt or by the 

 growth of peat. If the mode of filling up of the broads, as it is now going on, be 

 observed, it will be found that the peat encroaches from the edges. Hence, as 

 might be expected, we find the wider parts of the valleys to be those which are 

 occupied by broads, for it is evident that these would take longer to be filled. 

 But why should we find this feature in this part of England in particular ? Is there 

 any thing peculiar to Norfolk which may account for it? There is this. The 

 winter isothermal of 33° F. takes a course parallel to the eastern coast of England, 

 skirting the western extremity of Norway. Consequently we may well conceive 

 that, under a severer climate, glacial conditions would have lingered longer in the 



1 " Antiquity of Man," pp. 134-173. 



< For Mr. Rose's description of these deposits see Phil. Mag. vol. viii. p. 30, and Geol. Mag. 

 Vol. II. p. 8. For Mr. Trimmer's ditto, Journ. of Agricultural Society, vol. vii. p. 469, and 

 Geol. Journ. vol. vii. p. 23. 



' Rose, Phil, Mag., vol. viii. p. 34. * Ibid, p. 36, 



' Brit. Assoc, i860. See Geologist, 1861, p. 69. 



* Jour. Geol. Soc, vol. xxii. p. 562. 



