12 On Drift. 



Northern Germany. Throughout Russia and Poland it is laid 

 down in the map which accompanies the " Geology of Russia." 

 Independently of its zigzag irregularities, it may be considered 

 approximately as the circumference of a circle, having its centre 

 near the northern extremity of the Gulf of Bothnia. A very 

 large majority of the blocks dispersed over this immense area can 

 be distinctly referred to their Scandinavian origin, thus shewing 

 in a remarkable manner the centrifugal or radiating action already 

 mentioned of the forces by which this dispersion has been effected. 



The granite-boulders seem to have been in this, as in so many 

 other cases, the best travellers. They constitute the greater part 

 of the blocks in the external zone of the drift. But it is of more 

 importance to remark, that whatever may be the nature of the 

 blocks, they become almost universally smaller and more rounded 

 as we approach the external boundary above indicated. This 

 seems to me conclusive as to the nature of the transporting agency 

 in this outer zone. I can conceive water alone to be capable of 

 giving these characters to the transported materials. On the con- 

 trary, as we approach the central portion of this region of drift, 

 we find the blocks of enormous size, perfectly angular, and not 

 unfrequently imbedded in masses of fine drift, indicative of the 

 absence, at the time of its deposition, of any violent currents 

 capable of moving the blocks imbedded in it. In this we recog- 

 nise the transport by floating ice. And again, on the central land, 

 we recognise glaciers as the source of the floating ice, and the 

 means of transporting large angular blocks from their original sites 

 on the mountains to the level of the ocean. 



You will not suppose, gentlemen, that, in stating these conclu- 

 sions, I regard myself as opening new views to you. My object 

 is merely to present the subject to you in a general but compen- 

 dious form, in the hope that I may thus lead you to contemplate 

 its various points collectively, and to see how much they are 

 brought into harmony with each other by a distinct recognition of 

 the three causes above mentioned, and a due allotment of the 

 varied phenomena of the drift to their respective modes of trans- 

 port. 



The authors of the " Geology of Russia" consider the present 

 boundary of the region of the drift in North-eastern Russia as indi- 

 cating the approximate boundary of the glacial sea in that region 

 during the drift-period, and this conclusion appears to me per- 

 fectly legitimate. They also consider the low, flat lands of North- 

 ern Asia to have been, about the same period, under the sea. 

 In favour of this view, there appears to be the unequivocal, though 

 not perhaps abundant, evidence of marine remains. There seems 

 to be no evidence, however, of a submergence of this region ap- 

 proximating in depth to that of many parts of the European con- 

 tinent; the present low lands were probably covered only with 



