THE VERNAL MIGRATION 21 



record. In the interval — the wide interval between molten 

 heat and "eternal ice " — the Arctic lands have passed, 

 stage by stage, through every gradation of climate, and 

 have been, at one period or another, adapted for every 

 form of life — and that condition, it follows, these regions 

 would attain in advance of all other portions of the 

 earth's surface. Spitsbergen and Franz-Josef Land once 

 luxuriated in the profuse plant-life of the carboniferous 

 epoch. Incidentally I may mention having observed in 

 the first-named ice-bound land, palpable evidence of that 

 period of "grass and herb yielding seed" — though at 

 the present day neither tree nor shrub exist there — and 

 a small series of fossils brought home from Spitsbergen 

 proved to be identical with those of our own coal- 

 measures of Durham and Northumberland. 



The whole theory obviously depends, in the first 

 instance, on the presumption that the earth's axis has 

 remained comparatively stationary. But has this been 

 so ? This, again, is a problem, the answer to which 

 depends on a consideration of an intricate congeries of 

 facts and forces, all of which must be studied and their 

 effects calculated. Nor can they be examined sepa- 

 rately ; they must be regarded as a great moving whole, 

 a vast aggregation of forces acting and reacting on 

 each other with ever-varying results. The whole system 

 on which the earth moves through space, the effects 

 upon it of attraction, counter-attraction, and even such 

 complexities as the precession of the equinoxes, all have 

 their bearing on the question. It is, however, sufficient 

 here merely to name such awe-inspiring topics, and to 

 add that a consideration of them appears to justify a 

 conclusion that the earth's axis has not materially 

 altered in relation to the sun. 



