﻿Thos. Belt — The Glacial Period in Norfolk. 157 



north-west, as we know that it was of immense thickness in 

 Lancashire.^ 



Now if the brick-earths had been deposited before the ice reached 

 the coast, it seems not improbable that they should be contorted by 

 it and pushed up by the rising ice, so that in some cases the till would 

 be actually deposited below them. We find that the ice has certainly 

 accomplished this with the Lias, the Kimmeridge-clay, and the 

 Chalk, so that great masses of them are often found lying on till ; 

 and at the Ely Clay-pit there was a fine section open last summer, 

 showing highly inclined beds of Chalk, Kimmeridge Clay, and 

 NeocoQiian Sands, all underlain by till, and that by crushed and 

 disturbed beds of Kimmeridge-clay. 



Evidence of the passage of ice over the district has been found by 

 Messrs. Wood and Harmer in the valley of the Yare, the Wensum, 

 and the Little Ouse, and I have noticed it besides in the valleys of 

 the Waveney and the Ouse. 



I believe it was Mr. Croll who first pointed out that the bed of the 

 North Sea between Scotland and Scandinavia had been filled with 

 ice, and this opinion is now held by many geologists. In a letter^to 

 Nature in 1874, I remarked that, as up to the time of the Glacial 

 period the Straits of Dover did not appear to have been cut through, 

 it was evident that as soon as the northern end of the German Ocean 

 was blocked up by ice, a lake must have been formed, which drained 

 to the south-west, and gradually wore out a passage through the 

 Straits of Dover. This has appeared to many a rash speculation ; 

 but if any one will take the trouble to imagine what would be 

 the necessary result of stopping the flow of water to the north, 

 before the passage to the English Channel was open, he will find 

 that the theory is not an improbable one ; and I am glad to see that 

 it has been indorsed by Mr. Croll.^ 



At first, when the northern outlet was only partially obstructed, 

 the water would still be salt, though not so much so as the open sea, 

 and perhaps only stand a few feet above the present sea-level ; but 

 as the ice advanced, the water would rise until it overflowed the 

 isthmus that then connected England with the Continent, The 

 water of the lake would be fresh, or but slightly brackish, and I 

 suppose it was then that the laminated brick-earths, including those 

 of the lower part of the Thames Valley, were deposited. The Straits 

 of Dover were gradually cut through, and the brick-earths denuded, 

 whilst the ice from the north was slowly advancing southward. At 

 last, I suppose, the ice reached the coast of Norfolk, forced up great 

 masses of Chalk, and contorted and shifted the laminated brick- 

 earths. 



A branch of the ice-stream flowed up the Wash, and being re- 

 inforced, as before mentioned, from the north-west, reached certainly 

 as far south as Ely, and probably much further, sending off" a branch 

 along the depression now occupied by the valley of the Little Ouse 

 and the Waveney. 1 suppose that the ice in passing along the sea- 



1 Mr. R. H. Tiddeman, Quart. Journ. Geol. Soc. vol. xxviii. p. 471. 



2 Climate and Time, p. 452. 



