September 4, 1914] 



SCIENCE 



335 



remain always at right angles to this oscilla- 

 tion axis but to shift within the earth north 

 and south along the meridian of 10° east of 

 Greenwich. Thus the north pole is supposed 

 in the Pleistocene to have lain north of 

 Scandinavia and to be now advancing in the 

 direction of Bering Sea. In the Jurassic and 

 Cretaceous the continent of Europe is sup- 

 posed to have been in tropic latitudes. An 

 examination of the work of Eeibisch shows no 

 mention of the astronomic side of the problem 

 nor any reference to the work of G. H. Darwin. 

 His argument rests chiefly on various facts in 

 the distribution of animals and plants and 

 also upon the submergence and emergence of 

 certain regions. 



Kreichgauer in 1903 produced a map of the 

 polar wanderings through geologic time as 

 worked out by him, in which he shows the 

 poles actually changing place, the north pole 

 migrating from the Antarctic in the Pre- 

 Cambrian northerly through the Pacific Ocean, 

 through Alaska and the Arctic Archipelago to 

 Greenland, and thence to its present position. 



Jacobitti on the other hand prefers a differ- 

 ent path, his north pole lying in the South 

 Atlantic in Cambrian times, thence moving 

 easterly across South Africa, India, Australia, 

 the Pacific Ocean, Canada and Greenland to 

 its present location. 



Dr. Heinrich Simroth, professor in the Uni- 

 versity of Leipzig, elaborated the hypothesis 

 of Eeibisch, publishing in 190Y a book of 564 

 pages on "Die Pendulations Theorie." 



These hypotheses rest chiefly upon facts and 

 interpretations regarding the distribution of 

 plants and animals. Support for them is 

 also sought in the nature of crust movements 

 and in the geologic evidences of past cli- 

 matic changes. Much of the evidence is 

 vague in delimitation and in significance, 

 some of it is not clearly applicable, some of it 

 could be offset by opposing evidence, and all 

 of it can be given other interpretations which 

 find a better geologic basis and do not con- 

 travene the laws of mechanics. 



The writer has examined in some detail the 

 hypothesis of Eeibisch and Simroth, since this 

 is the one which has been most commended 



to geologists. Most of the foUowing criti- 

 cisms are directed toward their work, but in a 

 general way they apply to the other hypoth- 

 eses also. The kind of evidence upon which 

 Eeibisch founds a hypothesis involving a new 

 earth motion of which he is the discoverer is 

 seen in the following statements. He locates 

 his oscillation poles in Equador and Sumatra 

 because of botanical writings which claim that 

 the Tertiary floras of those regions were not 

 modified by Pleistocene climatic changes. 

 Archaic and related types of animals inhabit 

 these two antipodal regions, preserved from 

 extinction because of the constancy of climate 

 surrounding these oscillation poles. The 

 oscillation circle is at 90° to these poles, run- 

 ning north and south through Europe and 

 Africa. In the vicinity of this circle, climatic 

 changes, owing to the poles moving back and 

 forth on this meridian, are stated to have re- 

 peatedly driven out the faunas and floras and, 

 made this region that which has promoted the' 

 greatest evolutionary progress. Any other- 

 possible mode of accounting for the evidence- 

 these lands lie near his north-south belts of 

 greatest oscillatory climatic change and off- 

 set the arguments drawn from Equador and 

 Sumatra. The early Tertiary fauna pre- 

 served in Madagascar needs especially some 

 explanation since at that time this region ac- 

 cording to Eeibisch would have been near the 

 south pole. However such objections can 

 always be met and conquered by a sufficiently 

 ingenious advocate. 



All hypotheses of polar migration require 

 that there should be enormous changes of 

 figure of the earth in order that the surface 

 for every position of the axis should be in 

 approximate equilibrium. These changes in 

 the earth's body are supposed to take place 

 isostatically, with only a moderate lag. There 

 would be involved however a considerable 

 stretching of those parts of the crust advanc- 

 ing toward the equator because of the greater 

 equatorial circumference, compression in those 

 parts approaching the poles. Several advo- 

 cates have tried to read into the known crust 

 movements an agreement with these require- 

 ments. But as many conflicts as agreements 



