DESTINATIONS OF THE MIGRANTS. 199 



latitude or longitude is equally certain. I only 

 allude to this subject again in tlie hope of directing 

 research thereto ; it involves a much greater amount 

 of labour than I have yet unfortunately been able 

 to devote to it ; and would, to be dealt with at all 

 adequately, make far too wide a demand on the 

 space here available for its discussion. After all, this 

 little volume is but a pioneer in an almost unknown 

 land, and no one is more conscious than its author 

 of the utter impossibility of exhausting in a first 

 attempt so wide and so little worked a subject as 

 the Migration of Birds, even though that first 

 attempt embodies the research and observation of 

 a life-time. Its aim and purpose is but to point 

 the way to more elaborate and detailed investigation, 

 and to seek to rescue from chaos a branch of 

 Ornithological science as fascinating and as 

 absorbing as any alchemist's endeavour to accom- 

 plish the transmutation of gold ! 



That variation in Temperature was one of the 

 most powerful initiating causes of Migration we 

 have already seen ; it is only natural to presume 

 that it still continues to exert incalculable influence 

 on Migration ; otherwise w^e should not witness all 

 these intricate and complex phenomena that so 

 large a part of this volume has been written in the 

 earnest endeavour to describe and possibly to explain. 

 Depend upon it, the ebbing and the flowing of this 

 great tide of Avian Life is not governed by chance ; 

 the habit of Passage is too vitally important, too 

 deeply rooted, too grandly ancient, to have a trivial 



