TERRACES AND RIVER VALLEYS DP WESTERN EUROPE. 287 



question of time ; and who that has studied the phenomena of 

 the '• Great Ice Age " can doubt that the time was suffi- 

 ciently prolonged? 



2. The process of subsidence, greatest in the middle 

 glacial submergence of these islands, was probably more 

 rapid than that of emergence, though this is open to 

 question. At the present time the ocean waters are still 

 extending their range along the coasts of the British Isles 

 and of Western Europe. Si monivnentiim quceris. circumspice. 

 The south and east coasts of England attest the rapidit}^ 

 of the process. 



3. Nature of the rocks wider the floor of the ocean. — On this 

 point we can only fall back on conjecture, as the sounding 

 apparatus only brings up specimens of the soft superficial 

 deposits, such as sand, clay, or marl, thougli a general idea 

 of the nature of the solid floor may be gathered from that 

 of the adjoining lands. Dr. J. Joly. F.R.S., has recently 

 invented an apparatus in the form of an electrically driven 

 drill, by means of which cores of solid rock may be hollowed 

 out of the ocean-bed and be drawn to the surface.* 



III. Concluding Observations. — Having on a former 

 occasion pointed out how a great uprise of the ocean-bed 

 and adjoining lands on both sides of the Atlantic must have 

 affected the climatic conditions of these regions to the extent 

 of bringing about glacial conditions in these Isles,! I do not 

 propose to re-open the subject here, further than to observe 

 that we have in this uprise a simple and palpable cause of 

 the general lowering of temperature which took place 

 during the Pleistocene Epoch, and brought about glacial 

 conditions in the northern hemisphere. The prevalence of 

 Arctic conditions brought about by elevation would, it must 

 be remembered, be further accentuated by the uprise of the 

 Antillean continent, as demonstrated by Professor .1. W. 

 Spencer, owing to which the Gulf Stream would have been 

 unable to enter the Gulf of Mexico, and would have passed 

 into the North Atlantic with a, temperature much lower 

 than at the present day ; I have estimated this decrease at 

 12° Fahr. Such an explanation is in harmony with Lyellian 

 principles, which find in the relative distribution of land and 

 sea the causes which have governed conditions of climate in 

 past time. 



* Sclent. Proc. Roif. Dublin Soc, vol. viii, p. 509. 



t "Another possible cause of the Glacial Epoch," Trans. \'ict. Inst., 

 1898. 



