20 BIRD-LIFE OF THE BORDERS 



the present distribution and on the migrations of birds 

 {Ibis, 1887, p. 236, and 1888, p. 204). With respect to 

 the first-named point, all the salient facts relating to 

 present distribution of genera gleaned from the four 

 quarters of the globe are adduced by the learned 

 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 are of infinite 

 interest to naturalists. 1 



Beyond its general bearing on the correctness of the 

 whole theory, it is unnecessary here further to dwell on 

 that section of the subject — distribution. But I will 

 endeavour, in as few words as possible, to indicate the 

 influence of the Polar theory upon migration. 



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

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

 during unknown aeons it was gradually cooling, prepara- 

 tory to the reception of life. So much I assume. But the 

 cooling process 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 therefore 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 that intervene between intense heat and their 

 existing intense cold, is evidenced by their geological 



1 I find, at the last moment, that I have inadvertently overlooked the 

 fact that this "Dispersal" had already, some years previously, been briefly 

 foreshadowed by my friend Mr Howard Saunders, in his cosmic review of 

 the " Distribution of the Gulls and Terns " — Proceedings of the Linncean 

 Society ; 1878, pp. 405-406. 



