September 4, 1914] 



SCIENCE 



339 



but in the opposite quadrants from the uplifts. 

 This amounts to a shifting of matter from 

 two antipodal regions to regions 90° from 

 them, but on the same meridian circle. 



Erosion and sedimentation serve only to 

 transfer sediment from the high parts of a 

 continent to its low interior or its borders. 

 The limestones may be partly deposited in 

 other regions of the earth, but they constitute 

 not over ten per cent, of the sediments. Iso- 

 static readjustments would tend to affect the 

 regions unbalanced by erosion and sedimenta- 

 tion. All of these actions have had but little 

 tendency to shift matter from one octant of 

 the earth's surface to another octant. Such 

 surface processes have consequently had but 

 little effect in shifting the poles. 



The greater factor lies in the fragmentation 

 of ancient continents, assuming that the possi- 

 bility of this process be granted. But much 

 of the Pacific must always have been a reser- 

 voir for the ocean waters. The fragmentation 

 of Laurentia, extending the North Atlantic 

 ocean basin, would largely be balanced against 

 the sinking of Gondwana to form the South 

 Atlantic. Downsinkings in the Indian Ocean 

 and in the tropical Pacific would have but 

 little effect since they lie mostly within the tor- 

 rid zone. These down-sinkings, furthermore, 

 need not have caused to bulge up by just that 

 much some particular continent or continents. 

 The up-swelling to compensate for the down- 

 sinking may more readily be conceived as 

 affecting the whole earth. Fragmentation, 

 therefore, has not been areally distributed in 

 such a manner as to produce the maximum 

 effects calculated by Darwin as possible from 

 vertical changes of 10,000 feet. 



There is still another vital consideration, 

 however. Darwin considers the case where 

 elevation and subsidence is due to change of 

 density, but not change of mass. Taking a 

 superficial layer ten miles thick as not chang- 

 ing, but a swelling to occur throughout a sec- 

 tion of crust from ten to fifty miles in depth, 

 the change in the position of the axis would 

 be but .0126 of what it would be if the uplift 

 were due to an addition of matter. The perti- 

 nency of this is seen if it be noted that the 



great plateau uplifts of the Tibetan region 

 in Asia, of the Cordillera of North and South 

 America, have been upraised with an approach 

 to isostatic equilibrium from a state of low 

 elevation and broad submergence in the early 

 Tertiary. This is quite commonly viewed as 

 the result of an intumescence in the crust be- 

 neath, due perhaps to the irruption of magmas 

 and their accompanying heat and to the heat 

 of erogenic deformation. But Darwin's figures 

 show that uplifts due ,to this cause have a 

 negligible effect upon the axis of rotation. 

 Continental fragmentation and the sinking 

 of Mediterranean basins, to such extent as 

 they may have gone forward, may have been 

 due to some contrary process of increasing 

 density, the regional vertical movements thus 

 conserving the isostatic principle. 



From these considerations it is seen that 

 closer examination tends to cut down more 

 and more even those moderate limits of polar 

 migration set by Darwin. It would appear 

 that the .assumption of polar wandering as a 

 cause of climatic change and organic migra- 

 tions is as gratuitous as an assumption of a 

 changing earth orbit in defiance of the laws 

 of celestial mechanics. Unless some whoUy 

 unsuspected forces are at work within the 

 centrosphere, polar wandering has no more 

 basis in science than Symmes imaginings of 

 a hollow earth. From all that is known at 

 present the doctrine must be regarded as a 

 vagrant speculation, not as a working hypoth- 

 esis. ^ 



In closing this article it seems appropriate '\ 

 to indulge in a brief moralization. This paper \ 

 does not contribute any new facts, but was \ 

 written to show the untenableness of certain 1 

 hypotheses, emanating in this instance from ■ 

 Germany and in danger of spreading in 

 America, by confronting them with observed 

 facts and mathematical demonstrations, much 

 of which, originating in England and Amer- 

 ica, has been in the possession of science for 

 more than a quarter of a century. Does not 

 the history of this subject show the dangers of 

 over-specialization within one division of sci- 

 ence with the consequent putting forth of hy- 

 potheses regardless of the verdict of related 



