Peculiarities of Birds 109 



fry across the ocean. For instance White suggested 

 hibernation as a solution. The whole question, even 

 in this far advanced twentieth century, remains a 

 mystery. Birds are capable of sustaining life in rarified 

 atmospheres where other mammalia could not. By a 

 single mechanical ascert, they can reach within a space 

 of half a dozen miles or so, regions and conditions quite 

 beyond human knowledge, and can find meteorological 

 or atmospheric forces that mitigates the labours of or- 

 dinary flight, or possibly help them forward. Birds 

 travel infinitely higher than our limited vision can pene- 

 trate and in this latter consideration doubtless there is a 

 wide field for speculation. 



