1868.] 133 [Shaler. 



these are the alternations of elevation and subsidence, so frequently 

 observable in shore deposits of the present and former geological 

 period. Tliei'e is no way by which these actions are so easily expli- 

 cable as on the supposition of a change in the position of the pivot 

 point of such a movement of the earth's crust, as we have described. 

 The hypothesis demands the supposition of a constantly subsiding 

 ocean floor, or at least the absence of any general elevation of the 

 central regions of any ocean. This view is in accordance with 

 geological evidences. At all times in the earth's history we have 

 evidence of continued subsidence of ocean floors, taking place by a 

 movement so gradual that the deposition kept pace with the sinking, 

 so that thousands of feet of strata were laid down in an ocean which 

 remained always shallow. 



If we could accept the theory so ably presented by Mr. James 

 Crool, which assigns as the cause of the subsidence of the shores 

 within the glacial limits, the accumulation of ice about the pole, and 

 the consequent change in the position of the earth's centre of gravity, 

 then we might easily refer all the upward movements indicated by 

 raised beaches to such' action, and remove them from the purview 

 of the hypothesis Ave have just discussed. But as much doubt exists 

 as to the validity of Mr. Crool's hypothesis, it may not be out of 

 place to notice some facts which seem to militate against it. If his 

 view were correct, we should expect to find in regions of the same lat- 

 itude something like an equal amount of depression indicated by the 

 raised beaches, and other marks of littoral action. This does not 

 seem to be the case. The beach lines of the glacial period are much 

 higher on the North American than the European coast. At Brook- 

 lyn, in about the latitude of Naples, there are evidences of the sea at 

 one hundred feet above the water level. On Lake Cliamplain, on the 

 parallel of Cape Finesterre, at a height of about five hundred feet, 

 we have well defined littoral phenomena. The comparison might be 

 carried still farther with a prevailing result, that the North American 

 continent received a deeper submci-gence than the European shore 

 evinces. A comparison of regions near at hand affords us similarly 

 strong grounds for questioning the probability of equal submergence 

 of regions of the same latitude. Nowhere along the coast of Maine 

 have we shore lines more than two hundred feet above the present 

 level of the sea. Within the same parallels in Vermont the subsi- 

 dence was quite double that depth. 



It is true that all such evidence is of a negative character, and it 

 may be argued that if we had precise knowledge of the highest point 



