4 BIRD-MIGRATION 



Arctic Circle as the original cradle of life. From the 

 character of the fossil flora of Franz Josef Land and 

 Spitzbergen, it may be inferred that the climate in 

 these high latitudes was once tropical. Suppose the 

 earth, once a mass of molten mineral too fervid to 

 sustain organic life, gradually cooling down, it would 

 be at the poles where the temperature would first 

 become endurable by living creatures. Through long 

 seons the cooling process went on, till, at last, very few 

 forms of life could endure the winter cold in a region 

 where once tree - ferns towered and giant mosses 

 steamed. Winged creatures were driven forth, following 

 the organisms on which they depend for food ; yet to 

 this day the birds, drawn by a hereditary impulse, press 

 as far as possible northwards, towards the land of their 

 origin, to rear their young, bearing witness that in 

 Polar, not in Equatorial regions, lies the source of 

 animated nature. 



To understand the full force of this teaching, one 

 must take extreme instances of migration, such as the 

 knot and the curlew-sandpiper afford. These little 

 birds pass so far to the north to breed that it is 

 doubtful if any human eye has ever witnessed their 

 domestic arrangements. More than sixty years ago, 

 indeed, the knot was found in company with its newly 

 hatched young on the Parry Islands, Melville Pen- 

 insula, and Grinnel Land; and later, General Greely 



proprietor killed down the rabbits and planted up the warren, yet 

 still these stone curlews and their descendants continued to resort 

 to the place year after year, and reared their young in the unfamiliar 

 environment of dense woodland. 



