GEOGRAPHICAL DISTRIBUTION 175 



Though he did all that was in his power to forward 

 this study, the same note, almost of despair of solving 

 the great question, sounds in all his writings on the 

 subject of migration :- 



Lay down the paths of migrating birds, observe 

 their comings and goings, or strive to account for the 

 impulse which urges them forward as we will, there still 

 remains for consideration the most marvellous thing of 

 all How do the birds find their way so unerringly from 

 such immense distances ? 



A writer * in the Contemporary Review, giving a some- 

 what fanciful description of the " army of birds " on the 

 Spring Migration, remarked that it was " like the 

 Kingdom of Heaven which cometh not by observation." 

 Newton justly retorted that all we know of migration is 

 due to observation, and nearly all we do not know to 

 want of it. 



Closely connected with Migration is the Geographical 

 Distribution of Birds. The publication in 1876 of 

 Wallace's great book t was welcomed by Newton as an 

 event 



that will, if I am not mistaken, in after ages charac- 

 terise the present year as an epoch in the history of our 

 sciences inferior only in importance to that which marked 

 some eighteen or nineteen years ago the promulgation 

 of a reasonable Theory of Evolution by Mr. Darwin and 

 Mr. Wallace. And while it is to the latter of these two 

 naturalists that we owe the boon that has recently been 

 conferred on us, it is unquestionably from the former 

 labours of both united yet distinct that the boon 

 acquires its greatest value. 



He was careful, however, to add that he by no means 



* The Duke of Argyll, Contemporary Review, July, 1880. 



t " The Geographical Distribution of Animals, with a Study of the 

 relations of living and extinct Faunas as elucidating the Past Changes of 

 the Earth's Surface." By Alfred Ruseel Wallace, 2 vols. 



