434 NATURAL SCIENCE. Dec. 



These considerations may not be deemed conclusive, but neither is 

 the objection. We want more knowledge to speak positively either 

 way. Also we have not examined the whole of the Drift yet, so that 

 it contains many unknown possibilities. 



6. — A Subsidence of the land to the required depth is an improbability. 



I confess the attitude of mind which this statement discloses is 

 one I have a difficulty in comprehending. There is no known fact in 

 physical geology on surer foundations than that the land in all know^n 

 continents and islands has undergone considerable fluctuation of 

 level. Some land glacialists admit it as regards elevation and even 

 invoke former continental elevation as the cause of the Glacial Period. 

 They are unwilling to admit subsidence, but the clearest evidence up 

 to 5,000 feet is to be obtained in North America and to 1,000 feet in 

 Greenland, 9 and examples could be quoted from well nigh the whole 

 world. I am not speaking now of aught but post-Tertiary subsidence. 

 Our own coasts in the presence of buried river channels far below 

 low-water bear the marks of subsidence. If we are prepared to 

 dispute their evidence it will be necessary to recommence the study 

 of geology on a new basis. ^° There is no evidence of any kind to 

 indicate that this sort of elevation and subsidence takes place by or 

 is accompanied by faulting, but plenty to show that it is by the bending 

 of the earth's crust and differential vertical movement shading off to 

 nothing. 



Conclusions. 



Having now to the best of my ability fairly stated the case against 

 submergence as an explanation of the marine glacial beds, it will be 

 well to consider the general nature of the objections. A very little 

 examination will show that the criticisms are largely based upon 

 negative evidence, which may become invalid at any moment by 

 further discovery. 



The allegation of the extremely partial nature of the high-level 

 shelly gravels is, I have shown, not borne out by facts, and every 

 additional discovery of shelly drift weakens the argument. That no 

 perfect shells, or shells with the two valves in apposition, were to be 

 found in the Boulder Clay is an assertion that is already disproved, 

 and more examples in the same direction may be forthcoming. 



That the erratics, including in this term all foreign rocks whether 

 occurring as pebbles or boulders, are not found north of their origin, 

 is another objection which has not been proved. The absence of 

 deep-sea beds such as the land glacialists demand, is a further statement 

 of the same sort that it is impossible to prove. There remain, then, 



^De Ranee, Glacialists' Magazine, August, 1S93, p. 6. 



10 Since this was written. Dr. Geo. Dawson (Proc. Geol. Soc, Nov. 8) has 

 described the finding of Mammoth remains in the Pribilov Islands and Alaska, indi- 

 cating a former land-connection of the North American Continent with Asia, and 

 therefore a subsidence either during or since the Glacial Period. 



