TROCHlLIDiE — THE HUMMING-BIRDS. 441 



ica, either in the islands or on the continent, and number in all not far from 

 four hundred species, distributed into various subdivisions and genera, but 

 all possessing, to a very large degree, the same common peculiarities, of 

 which the well-known Kuby-throat of eastern North America may be taken 

 as eminently typical. The habits and peculiarities of this numerous family 

 have been closely studied, and many valuable facts in relation to them have 

 been contributed by various naturalists ; by none, perhaps, with more intelli- 

 gent attention than by the eminent Swiss naturalist, M. H. de Saussure, in 

 his visit to the West India Islands and Mexico, to whose observations 

 we are largely indebted. 



On the first visit of this naturalist to a savanna in the island of Ja- 

 maica, he at once noticed what he at first took to be a brilliant green insect, 

 of rapid flight, approaching him by successive alternations of movements 

 and pauses, and rapidly gliding among and over the network of interlacing 

 shrubs. " He was surprised by the extraordinary dexterity with which it 

 avoided the movements of his net, and yet more astonished to find, when he 

 had captured it, tliat he had taken a bird, and not an insect. 



He soon satisfied himself that this entire family not only have the form 

 and aspect of insects, but that they have also the same movements, the 

 same habits, and the same manner of living, with certain insects. Their 

 fliglit is exactly like that of an insect, and in this respect they form a re- 

 markably exceptional group among birds. When we notice their long wings 

 in our cabinet specimens, we naturally suppose that they use these instru- 

 ments of flight in the same manner with the Swallow or the Swift. Yet 

 investigation shows that, so very far from this, these wings, comparatively so 

 very long, vibrate even more rapidly than do those of birds with .proportion- 

 ately the smallest wings, such as the Grebe, the Loon, and the Penguin, and 

 that, more than this, they vibrate with an intensity so vastly superior, that 

 they become wholly invisible in the wonderful rapidity of their movements. 



The altogether exceptional character of their flight is a subject for never- 

 ceasing astonishment. Until we actually witness it, we should never con- 

 ceive it to be possible for a bird to vibrate its wings with so great a rapidity, 

 and by them to support itself in the air in the same manner with the Anthraces 

 and other aerial insects. This feat is rendered all the more surprising by the 

 extreme narrowness of the wing and the comparative weight of the body, 

 which is quite considerable, on account of the compactness of the flesh and 

 bones, and the small size of the birds themselves, whose wings displace but 

 a small quantity of air. The resistance of the air to the stroke of the wing 

 of a bird should be, not in proportion to the surface of that wing, but to its 

 square, or even to its cube, if the movement is very rapid. Hence it follows 

 that a due proportion being required as between the weight of the body and 

 the surface of this organ, a small bird cannot keep itself poised in the 

 air except by means of vibrations more rapid than those of a larger kind. 

 This is, without doubt, one explanation of the fact tliat Humming-Birds, in 



VOL. II. 56 



