By the Rev. A. C. Smith. 241 
framework, and clothed with a plumage in specific gravity but little 
exceeding the air itself, we are at no loss to understand the ease 
with which birds mount from the earth and soar among the clouds; 
but to enable them to pass quickly through the air, to progress 
rapidly and without fatigue, no instruments could be desired more 
excellent than the wings with which they are provided; so light 
and yet so vigorous; furnished with such strong muscles; so spacious 
when extended in flight, and yet so compact when closed in rest. 
By the help of these oars or sails they can strike the air so forcibly, 
and with such a succession of rapid and powerful strokes, as to 
impel forward their bodies with wonderful velocity: the greater 
the extent of the wings, in proportion to the size of the bird, the 
greater is the facility with which it can sustain itself in the air, and 
the greater the rapidity of its flight: as an example of this, 
compare the stretch of wing and the proportionate speed of the 
common swift and the common sparrow. Almost all species can 
fly with exceeding swiftness, but the progress of some is so very 
rapid, as rather to rival the velocity of the arrow from the bow, than 
the movements of any other creature: yet, with such amazing power, 
what can be lighter than the materials of which the wings are 
formed? the bones hollow and filled with air, the muscles strong 
and unincumbered by flesh: the feathers large like sails, and of 
exceeding buoyancy. Then again in like manner, what can be more 
perfect than their tails? these too are only composed of feathers, but 
they serve as rudders, enabling them to steer their course through the 
air at pleasure with the greatest ease and with the greatest accuracy. 
Thus when we look at the external formation of a bird, we can 
but admire its symmetry and elegance, the buoyancy and lightness 
of its frame, so admirably adapted for flight: but not less perfect 
nor less calculated to excite our admiration in its internal structure. 
Is a bird furnished with bones and muscles so absolutely necessary 
to its aerial evolutions? but mark how thin and light are the 
bones, how delicate the muscles, those only excepted which are 
adapted for moving the wings. Then again observe the lungs: 
small indeed they are, but so placed, and the air so introduced into 
them from the windpipe, that in passing it is conveyed into certain 
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