TUOCIIIMD.K — THE IIl'MMING-BIRDS. 441 



ica, eitlior in the isliuids ov on tlie continent, ami number in all not tar from 

 lour liundred species, distriliutoJ into various subdivisions and genera, but 

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

 which the well-known iJuljy-throat of eastern Nortii America may be taken 

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

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

 been contributed l)y 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, lie at once noticed what he at first took to be a brilliant green insect, 

 of rapid flight, aiijiroaching him by successive alternations of movements 

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

 shrubs, lie was surprised l)y 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. Tlieir 

 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 tlie Swift. Yet 

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

 very long, vibrate even more rapidly than do those of Ijirds with projiortion- 

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

 that, more than tliis, they vibrate witli an intensity so vastly superior, that 

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



Tlie altogether exceptional character of their Hight is a subject for never- 

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

 ceive it to l)e possible for a l)ird to vibrate its wings with so great a rapidity, 

 and by them to sui)))ort itself in the air in the same manner witii the Anthvaccs 

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

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

 which is (piite considerable, on account of the compactness of the flesh and 

 bones, and th(i small size of the birds themselves, whose wings di,splace 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 ita cube, if the movement is very rapid. Hence it follows 

 tliat a due pro])ortion being re(piired as between the weight of the body and 

 tlie 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. 

 Tliis is, without doubt, one explanation of the fact that Hummiug-IJirds, in 



vol,, II. 56 



