246 NEOZOIC TIME. [CHAP. XII. 



to have been derived from Carboniferous, Lower Creta- 

 ceous, and Eocene rocks. There is a total absence of 

 Jurassic debris and of the liver-coloured quartzites which 

 are so common in the English Trias. " In fact," to quote 

 Mr. Reid, 1 " if the river had flowed from the south, west, 

 or north, it must have brought quite a different collection 

 of stones. From the north-east [had it come from that 

 direction] it would probably flow entirely over chalk. It 

 therefore seems that only from the south-east or east could 

 the stones be derived." This conclusion, as will be seen in 

 the sequel, is an important factor in the restoration of the 

 physical geography of the North Sea area at this particular 

 time. 



Near Cromer these terrestrial deposits are succeeded by 

 the Leda myalis bed, which is from 4 to 15 feet thick, and 

 consists of fine loamy sand with marine shells, some of 

 them lying undisturbed in the position of life. It is clear, 

 therefore, that the last change which occurred in this por- 

 tion of the Pliocene area was a submergence which brought 

 in the sea once more over the lower parts of the newly- 

 formed land. This, however, seems to have been only a 

 temporary change, followed by an elevation of much greater 

 extent, during which the climate underwent an enormous 

 alteration. 



2. Geographical Restoration. 



Miocene Time. It will be remembered that the Oligocene 

 epoch was described as one of gradual upheaval, and as 

 closing with a general elevation of western Europe in 

 which the British region participated. That this continental 

 period lasted a long time is proved by the great change 

 which took place in the molluscan and mammalian fauna. 2 



1 " Geology of Country around Cromer, Mem. Geol. Surv.," p. 56. 



2 See "Historical Geology," p. 489. 



