570 A NATURALIST ON THE "CHALLENGER." 



various stages of perfection in the shaping of the wings, and the 

 skill of the use of them shown by the birds. Eefinement in the 

 art of the use of the wings by birds seems to run in two different 

 directions. The flight of the Albatross, regarded as the per- 

 fection of one mode, the soaring method, performed by aid of 

 great length of wing, may be contrasted with that of the 

 Humming Bird, equally perfect in its way and far more rapid, 

 but performed by the use of short wings and excessively rapid 

 motion of them. 



The movement of the Albatross may be compared to that of 

 a skilful skater on the outside edge ; the Humming Bird's flight 

 is just like that of an insect. The Albatross ekes out to the 

 utmost the momentum derived from a few powerful strokes, and 

 uses it up slowly in gliding, making all possible use at the same 

 time of the force of the wind. 



I believe that Albatrosses move their wings much oftener 

 than is suspected. They often have the appearance of soaring 

 for long periods after a ship without flapping their wings at all, 

 but if they be very closely watched, very short but extremely 

 quick motions of the wings may be detected. The appearance 

 is rather as if the body of the bird dropped a very short distance 

 and rose again. The movements cannot be seen at all unless 

 the bird is exactly on a level with the eye. A very quick 

 stroke, carried even through a very short arc, can of course 

 supply a large store of fresh momentum. In perfectly calm 

 weather, Albatrosses flap heavily. 



The Great White Albatrosses which are seen behind ships, are 

 usually by no means beautiful objects. The long wings look 

 far too long for the body, and being so narrow, the body looks 

 heavy and out of proportion to them. Further, five out of six 

 of the birds seen are young ones, in immature brown plumage, 

 and look dirty and draggled. The old birds when in their best 

 breeding plumage, as seen on their nests, are handsome enough. 



Whilst on the subject of flight, I would say a few words 

 about the flight of the Flying-fish. Dr. Mobius has lately pro- 

 duced an elaborate paper* on the much vexed question as to 



* K. Mobius, Die Bewegungen der fliegenden Fisclie durch die Luft 

 z. fur. Wiss. Zool. 1878, s. 343. 



