Structure and Flight 



our winter migrants from Norway rise to such a 

 height that England becomes visible ere they are 

 out of sight of the land they left. And this journey 

 across the North Sea is made (every autumn) by 

 vast numbers of so frail a creature as the Golden 

 Crested Wren, the smallest of British birds. It is 

 true that numbers sink exhausted on the rigging 

 of fishing boats and many are doubtless drowned, 

 but that makes the fact that so many are successful 

 none the less wonderful. 



Let us look at the principles of flight, which are 

 now occupying the attention of man to a hitherto 

 unparalleled extent. Nature overcomes the diffi- 

 culties by conforming to law, and in this connec- 

 tion there are three great laws of which we must 

 take note. The first is the law of gravitation ; the 

 second, that the air offers resistance to any body 

 passing through it ; and the third, that every force 

 has an equal and opposite reaction. 



By certain contrivances, these laws, apparently 

 hostile to flight, are, as it were, conquered by 

 obedience and actually made to assist it. The 

 law of gravitation is a statement of the tendency 

 of a body towards the centre of the earth, surely 

 a serious obstacle to aerial navigation. There is a 

 popular impression that prior to flight a bird 

 inflates itself with air until it becomes as light as 

 the element in which it flies, but a moment's thought 

 will show the fallacy of such an idea. If the bird 

 were as light as air, it would float as helplessly as 



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