236 THE GLACIAL OR ICE EPOCH. 



second stage of the glacial epoch, and must have been 

 characterised "by all that glacier on land or iceberg on water 

 are capable of performing. The ice-sheet that now gathered 

 over the gradually -decreasing land would push its way 

 shoreward with its annual burden of debris, and this de- 

 bris, as it was carried seaward, would be dropt in part over 

 the clay, shingle, and boulders that had been accumulated 

 during the first stage. Of course, a considerable portion of 

 the debris of the first stage would be removed by shore 

 denudation as the land subsided, but a large portion was 

 also left undisturbed ; and thus it is that we find in many 

 places the earlier clays and angular blocks covered over by 

 other clays, replete with boulders more worn and rounded, 

 and more strongly marked by scratches and furrows. It 

 was then, and during this period of subsidence, that huge 

 boulders were carried by floating ice far from their parent 

 rocks ; and thus it is that these boulders, now hundreds of 

 miles from their original cliffs, mark in a special manner 

 the second stage of the glacial epoch.* During this stage, 

 as during the preceding, we have no evidence of a terres- 

 trial flora or fauna, the climate being evidently too rigorous 

 for their support ; and it is only towards the southern 

 limits of the ice-field (the 40th or 42d parallel of lati- 

 tude t) that we can expect to find the remains either of 



* It is difficult to convey by description the difference between the 

 clays and boulders of the first and second stages ; but a few days in the 

 field will train the eye sufficiently to mark the distinction, and this 

 altogether independent of superposition. There is a roughness of ad- 

 mixture and heterogeneousness about them that never appear in those 

 of the earlier stage. Perhaps the best test of the second stage is the 

 number of " erratic blocks," or boulders far removed from their parent 

 rocks. In Europe, Scandinavian rocks are found in Central Germany 

 and over the south-east of England ; in North America, Canadian blocks 

 occur a hundred and a hundred and fifty miles southward of their 

 parent sources. 



t American geologists give the southern limit of the drift in their 



