﻿EXTERNAL ANATOMY. WING FEATHERS. 83 



quality through almost every one of the minor groups 

 of the perching birds. Taking the other extreme of 

 slowness, we find that all birds belonging to or repre- 

 senting the rasorial order, have the shortest wings, and 

 consequently the most imperfect flight. Not to mention 

 our domestic poultry, including the fowl, Guinea hen, 

 turkey, and peacock, there is the whole of the ostrich 

 family, to whom the power of lifting their heavy bodies 

 from the earth is altogether denied. Between these two 

 orders, or primary types, stands the grallatorial, which, 

 in this respect, is not greatly inferior to the aquatic, but 

 yet vastly superior to the rasorial. We accordingly find 

 that its prototype among the perchers, which is the 

 tenuirostral tribe, is only inferior to the swallows. A 

 humming-bird, indeed, appears to fly with greater 

 swiftness than it really does, because, from its very 

 diminutive size, the eye no sooner discerns it than it 

 disappears ; but this, in some measure, may be the effect 

 of size, more than of pre-eminent rapidity in flight. 

 Admitting, however, that a humming-bird passes 

 through the air even with greater celerity than a 

 swallow, they differ materially in the power of sustain- 

 ing flight. The one can remain on the wing for hours, 

 while the other, after probing the tubes of a flowering 

 shrub, generally perches upon one of its naked twigs, 

 for the obvious purpose of rest. In the two remaining 

 orders of birds, the powers of flight are very unequal. 

 In the raytores, which immediately follow the natatores, 

 we accordingly find this faculty considerably developed : 

 for of all land birds, excepting, perhaps, the swallows, 

 none are so swift or vigorous on the wing as the eagles 

 and falcons. Lastly, we have the insessorial or perch- 

 ing order, where the flight is only moderate : it is less 

 rapid, indeed, than that of the raptores; but more per- 

 fect than in the rasores. These facts lead to a very 

 curious result ; for they establish a circular series in the 

 development of that faculty most characteristic of the 

 whole class. The maximum of flight is found in the 

 natatorial order, from which it branches off, as it were, 

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