14 BIRD-LIFE OF THE BORDERS. 



in relation to its bearings both on the present distribution and 

 on the migrations of birds (Ibis, 1887, p. 236, 1888, p. 204). 

 With respect to the first-named point, all the salient facts 

 relating to present generic distribution, gleaned from the four 

 quarters of the globe, are adduced by the accomplished Canon 

 of Durham, and the various steps of evidence by which the 

 North Polar region is shown to have been the original centre 

 of dispersal of all life, should be carefully read by all 

 ornithologists. 



Beyond its general bearing on the correctness of the 

 whole theory, it is unnecessary at present further to dwell 

 on that section of the subject ; but I will endeavour, in as 

 few words as possible, to indicate the influence of the Polar 

 theory on migration. 



It must, in the first place, be granted that our globe was 

 "in the beginning" a molten, lifeless mass; that during 

 unknown reons it was gradually cooling preparatory to the 

 reception of life. So much I assume. But the cooling pro- 

 cess would clearly not proceed with equal speed. Those 

 portions of the earth which are furthest removed from the 

 power of the sun, and which most rapidly radiate their heat 

 into space, would necessarily be the first to cool, and there- 

 fore the first to become capable of maintaining life. These 

 colder portions {provided that the axis of the globe has not 

 materially altered in relation to the sun) would be the Polar 

 regions — Arctic and Antarctic. That the North Polar region 

 has so passed through all the stages from intense heat to 

 their existing intense cold, is evidenced by their geological 

 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. 

 Spitzbergen and Franz-Josef Land have once luxuriated in 

 the profuse wealth of plant-life of the carboniferous epoch. 

 Incidentally I may mention having myself witnessed in the 

 first-named ice-bound land palpable evidence of that period 

 of "grass and herb yielding seed, and fruit tree yielding 

 fruit " — though at the present day not a tree or a shrub 

 exists there — and a small series of fossils brought home from 



