l62 THE REIGN OF LAW. 



possible variety of direction without requiring 

 to give a single stroke to its pinions. Now, 

 the Albatross has the extreme form of this 

 kind of wing. Its wings are immensely long 

 - — about fourteen or fifteen feet from tip to 

 tip — and almost as narrow in proportion as 

 a riband* Our common Gannet is an excel- 

 lent, though a more modified, example of the 

 same kind of structure. On the other hand, birds 

 of short wings, though their flight is sometimes 

 very fast, are never able to sustain it very long. 

 The muscular exertion they require is greater, be- 

 cause it does not work to the same advantage. 

 Most of the gallinaceous birds (such as the common 

 Fowl, Pheasants, Partridges, &c.) have wings of this 

 kind ; and some of them never fly except to escape 

 an enemy, or to change their feeding ground. 



* The mechanical principle involved in the sufficiency of very- 

 narrow wings has, I believe, been adequately explained in a very 

 ingenious Paper read before the Aeronautical Society, by Mr F. H. 

 Wenham, C. E. It is the same mechanical principle which accounts 

 for the narrow blades of a Screw Propeller having a resisting force 

 as great as would be exerted upon the whole area of rotation by a 

 solid Disc. In the case of a flat body, such as the wing of a Bird, 

 being propelled edgeways through the air, nearly the whole resisting 

 and sustaining force is exerted upon the first few inches of the ad- 

 vancing surface. 



