160 NORFOLK DRIFT. [Ch. XII. 



gravel and sand of a sea beach and of a river's bed, wlien organic re- 

 mains are wanting ; but, on the other hand, when we consider the 

 general rarity of shells in drift which we know to be of marine origin, 

 we cannot suppose that, in the shelly sands of Moel Tryfaen, we have 

 hit upon the exact uppermost limit of marine deposition, or, in other 

 words, a precise measure of the submergence of the land beneath the 

 sea during the glacial period. 



We are gradually obtaining proofs of the larger part of England 

 north of a line drawn from the mouth of the Thames to the Bristol 

 Channel, having been under the sea and traversed by floating ice since 

 the commencement of the glacial epoch. Among recent observations 

 illustrative of this point, I may allude to the discovery, by Mr. J. F. 

 Bateman, near Blackpool, fifty miles from the sea, and at the height 

 of 568 feet above its level, of till containing rounded and angular 

 stones and marine shells, such as TurrUella communis, Purpura 

 lapillus, Cardium edule, and others, among which Trophon clathratum 

 (=zFusus Bamffius), though still surviving in North British seas, in- 

 dicates a cold climate. Drift of similar character covers a large part 

 of Ireland, although marine shells have not been detected in it at 

 greater height than 600 feet, and very rarely higher than 500 ; but 

 there can be no doubt that that island, like the greater part of Eng- 

 land and Scotland, was for ages an archipelago traversed by floating ice. 

 There was first a period when Ireland formed part of the continent of 

 Europe, from whence it received the plants and animals now inhabit- 

 ing it. In some part of this period its rocks were largely smoothed 

 and striated by ice-action in the more mountainous regions. After this 

 there was great subsidence, and the conversion of the island into an 

 archipelago, followed by a re-elevation of land and a second continental 

 period, and, after all these changes, a final separation from England and 

 Wales.* 



Norfolk Drift. — In England the monuments of the period of sub- 

 mergence can nowhere be so advantageously studied as in the cliffs of 

 the Norfolk coast between Happisburgh and Cromer. Vertical sections, 

 varying in height from 30 to 300 feet, are there exposed to view for a 

 distance of about fifty miles, where the series of formations, beginning 

 with the lowest, is as follows : — First, chalk, with flints in nearly hori- 

 zontal strata ; secondly, Norwich Crag, or a marine tertiary formation 

 of the Newer Pliocene era, which extends from Weybourne seven miles 

 to Cromer, and then thins out ; thirdly, the forest bed, chiefly com- 

 posed of vegetable matter, with scattered cones of the Scotch and 

 spruce firs, and many other recent plants, and with bones of the ele- 

 phant and of other extinct and living species of mammalia. In this 

 forest bed the stumps of many trees stand erect with their roots in an 

 ancient soil. Fourthly, a fluvio-marine series, with abundant lignite 

 beds, and with alternations of freshwater and marine strata of sand 



* See Antiquity of Man, by the Author, chap. xiv. 



