G. R. Wieland — Polar Climate in Time. 403 



composition of the atmosphere, seasonal distribution of light, 

 and orbital eccentricity. 



J^Tow a point of prime importance when we come to the con- 

 sideration of such topics in connection with the fossil record 

 is the vivid impression we get of the general stability of the 

 globe, and of the main features of climate tliroughout very 

 long periods of time. The facts of the fossil record lend 

 much of reality to our ideas of the relative or the actual per- 

 manence of matter. But it would only be presumption on the 

 part of one who has interested himself almost entirely with 

 biological studies to attempt an arbitrament of the results of 

 research on fundamental physical and astronomical subjects. 

 It will, however, doubtless suffice for the purposes of the 

 present argument if but two of the above climatic factors sub- 

 ject to secular change, — namely, axial fixity .^ and orbital eccen- 

 tricity^ be here mentioned at any length. 



Axial Fixity. — Variations of latitude due to motion of the 

 poles are theoreticall}^ due to mountain making, denudation, 

 and glacial ice caps, and though slight, have with increasing 

 reiinement of astronomical measurement become determinable. 

 As the result of prolonged calculation Dr. S. C. Chandler of 

 Cambridge finds evidence of polar shifting in all reliable 

 observations since 1750. From the available data he finds the 

 motion of the pole to be a much varying component arising 

 from an annual revolution in a narrow ellipse about 30 feet 

 long, but varying in form and position, and a revolution in a 

 circle about 26 feet in diameter with a period of about 428 

 days. 



According to Croll, the shifting of the southern ice caps to 

 the north would move the earth's center of gravity from 500 

 to 1000 feet, but this would in part be compensated by oceanic 

 shifting. It is evident that the change from this cause must 

 be slight. And Lord Kelvin holds that the equatorial bulge 

 is such that no geologic changes of surface could have possibly 

 altered the position of rotation sufficiently to sensibly affect 

 climate. 



^or is it likely that accumulations of extra-terrestrial mate- 

 rial in some one quarter of the globe could ever have had such 

 an effect. If so, there should be some stratigraphical evidence 

 of occasional local large aerolitic deposits. But none are 

 known and the facts indicate that in the long run the surface 

 of the globe has as a whole received accretions from without 

 about equally. Beyond the slight movements above given 

 there is, therefore, no evidence of departure from a relatively 

 fixed position of the earth's axis, and until direct evidence has 

 been adduced, it is both legitimate and necessary to set aside as 

 valueless all mere speculations to the contrary. 



