LECTURE XI. 313 



thickness. It overlies the platforms^ follows tlie slopes of 

 mountains down to the valleys^ it forms frequently the bottom 

 which prevents rivers from further excavating the valleys ; it 

 contains in the North large angular erratic blocks^ or rounded^ 

 scratched^ and striated rolled stones in the vicinity of the Alps 

 and the Scandinavian mountains. Where the formation re- 

 poses upon solid rocks, the latter are polished, grooved, and 

 striped hke the rocks passed over by a glacier. Most geolo- 

 gists of the present day agree as to the origin of this formation. 

 It is the glacial loam produced by the grinding of the rock 

 under the weight of the moving ice masses, which also pro- 

 duced the scored stones. "Where these latter only exist, it is 

 the lower moraine which so presents itself; but where large 

 blocks occur, then either the earth-moraine has coalesced with 

 the fundamental moraine, or the angular blocks have been 

 carried upon the moving ice masses and deposited in the loam. 



On taking, for the present, this formation as a starting 

 point, we find that but few land and fresh-water deposits are 

 known which intervene between this formation and the tertiary 

 period. That the tertiary period did not suddenly enter the 

 glacial epoch, seems to be proved by the condition of those 

 tertiary strata known in England as " crag." There was also 

 found, near Cromer, on the Norfolk coast, a group of beds 

 underlying the glacial loam, but characteristicallj'' distinct from 

 the tertiary period. There are sunken forests which, in many 

 spots, are exposed at low water. The roots of the broken off 

 trunks are still in their natural position, and the loam in which 

 they are imbedded is black from the intermixture with vege- 

 table matter. The fir, pine, yew, alder, oak, and sloe grew 

 here in a marshy soil, in which the white, and yellow water 

 lilies, marsh-trefoil, frogsbit, and other aquatic plants of our 

 present Flora, were found. There were also discovered fossil 

 bones of three species of elephants, of the mammoth, rhino- 

 ceros, hippopotamus, of the extinct large beaver, of horses, 

 oxen, deer, the common beaver, and the water rat, of the wal- 

 rus, the narwhal, large whales whose carcasses had been washed 

 ashore. 



This fresh-water formation, the insects and shells of which 



