130 THE MIGRATION OF BIRDS 



and the insects and plants upon which they feed, 

 we share a common heritage, and the more we learn 

 of the life of these, our fellow workers, the nearer 

 we approach solution of the great riddle of the 

 Universe, the mysterious law-abiding scheme of 

 Nature. The book of knowledge to which we may 

 add some iota is marred with mystery, superstition 

 and error, but each proved fact cleanses its pages. 

 ' Facts/' says Laing, ' ' are the spokes of the ladder 

 by which we climb from earth to heaven/' 



