496 Seeley — Gravel and Drift of the Fenlands. 



an elevation affected Western Norfolk. But were it so or not, at 

 Hunstanton there terminates a cliff whicli reappears over the Wash 

 at Wainfleet with the same rocks ; and were these cliffs connected, a 

 Cretaceous barrier would dam out the sea, and no Crag could be formed 

 in the Fens. And as there is no evidence that it could have been 

 exposed to the sea diu-ing the Tertiary periods, I am prepared to 

 suggest that, before the Drift began, this barrier was not broken 

 through. 



At the close of the Crag age, as the island was subsiding, every 

 part of it must have come successively under the action of the 

 breakers ; and the result — denudation. But of the detritus the traces 

 are not clear. For when the Boulder-clay appears, so far as may be 

 judged from included fragments, it is not to any extent a drift 

 of local detritus, but came sweeping down from the land of Plutonic 

 and old-life rocks, whose hills seem to have been sawn and grated 

 with ice. It may be that, during this earliest Drift age, — 

 Ice, mast-high, came floating by, 

 As green as emerald, — 



but I have not found in this locality a vestige of iceberg action. Of 

 glacier action the deposits of the Fenlands offer no traces, unless 

 the fragments of northern rocks be held to prove that one great 

 glacier stretched from the Tweed to the Thames, of which there may 

 be as much likelihood as that the ice of the Caucasus excavated the 

 Black Sea. This may have been a long, slow period, for under the 

 Norfolk drift are shells ; in the Boulder-clay are shells ; and marine 

 shells are met with at every elevation up to the top of Moel Tryfaen 

 Some may have come with the drifted material; but wb ether living 

 near where found, or brought from afar, they equally indicate a 

 continuous sea shore changing so slowly that the life of the margin 

 followed it. 



In the typical section at Hasborough, in Norfolk, Boulder-clay 

 covers the laminated beds, and is overlaid by the contorted drift; 

 above this is an Upper Boulder- clay, and finally gravels. The 

 Boulder-clay of Muswell Hill, near London, that of Ely, and the 

 Lower Boulder-clay of Norfolk, contain the same rocks, and present 

 substantially the same characters. The Hunstanton Eed Eock occurs 

 at Muswell Hill, at Ely, and on the Norfolk coast. The Ely Boulder- 

 clay contains thick specimens of Tellina, exactly like those so char- 

 acteristic of the Norfolk Boulder-clay. This, to me, suggests that 

 the Ely deposit is as old as the old Boulder-clay of the Eastern 

 Counties. I am, moreover, led to believe that it is the oldest drift 

 of the Cambridge district, from the fact that it rests on beds 

 which have since been removed from the country round, and that it 

 would almost have disappeared but for the fault letting down a 

 wedge of it into the Eoswell pit, where it is at least some 60 feet 

 thick. And measurements show that, at the date of the fault, Ely 

 Hill must have been from 100 to 200, or more, feet higher than 

 it is now. 



The regular character of the Boulder-clay on the Norfolk coast 

 would lead to the conclusion that it was somewhat uniformly spread 



