BIRD. 



391 



their mechanical boasting-, and even their mechanical 

 science, have found that they would require to go a 

 long time to school before they could accomplish even 

 the most apparently simple of those objects. A 

 flying apparatus, to be moved by the human arms, 

 is, like the kindred fancy of a perpetual motion, a 

 physical impossibility, and the attempt to construct 

 one is one of those absurdities into which men are 

 apt to fall in the infancy of knowledge, when they 

 have vanity enough to lead them wrong, but want 

 the requisite knowledge for keeping them right. Even 

 if the arms could be trimmed to perfect wings, bearing 

 the same proportion to the weight of the human body 

 as those of the bird of most powerful flight have to its 

 weight, there are not in the human body any muscles 

 by which such wings could receive any thing like a 

 flying motion. Then, if that difficulty could be got 

 the better of (which it evidently could not), the spine 

 would bend, the body cant over, and tumble to the 

 ground on whatever part happened to be the heaviest. 

 Or, if this again could be got the better of, man is 

 not adapted for breathing on the wing, and thus the 

 circulation would stop, and there would be an end of 

 the flier in the very beginning of his flight. In short, 

 it may be said without fear of contradiction that no 

 addition to the human body could make man a flyer. 

 If the study of the structure of birds had no other 

 effect than the preventing of such fancies as these 

 fancies which, like the other absurdity mentioned, 

 still sometimes occupy time in which the schemer 

 might do something not altogether useless it would 

 be worthy of our attention. The writer of this article 

 remembers, long ago, a case in which a young man, 

 in a small country town, had got so much of the 

 formal or colloquial part of science, that he was 

 looked upon as a prodigy, and, among other things, a 

 very Archimedes in mechanics. Earth could not set 

 bounds to his ambition, and he would needs fly : 



not more complicated in its organisation than me 

 slowest-paced of the mammalia. But the bird, when 

 its habit is to be much on the wing, is all-over adapted 

 for flight, and the system of its mechanics, if we could 

 fully comprehend it, would certainly be the most curi- 

 ous, and far from the least instructive, in the whole 

 of the animal kingdom. 



The buoyancy, as well as the upward motion, is not 

 very difficult to. understand, because the wing, from its 

 general form, and the structure of the feathers, rises 

 with much less effort than it descends. Thus the 

 constant tendency of the powerfully- winged bird is to 

 mount upwards, and on this account the firmest 

 bird, that which with the same volume of body and 

 extent of wings, has the greatest specific gravity, is 

 the best flyer, flies more steadily, and apparently with 

 less effort. This must, of course, have a limit ; be- 

 cause, leaving the incapacity of breathing out of the 

 question, no bird could fly in a vacuum, and thus 

 there must be a certain density of air which is the 

 best adapted for the flight of any given species of 

 bird. This appears, even in the case of heavy birds, 

 to be considerably less than the density of the mean 

 level of the earth's surface. Eagles are heavy birds, 

 even for their powerful wings, and yet they are high- 

 fliers, even when their abodes are at great elevations 

 in the mountains. All birds which take long flights 

 fly high, whatever may be their other habits. Wild 

 lieese, herons, all birds indiscriminately "take the 

 sky " when they set out upon long journeys. In some 

 this may be in part done to avoid enemies or obstacles, 

 but the habit is too general for being accounted for 

 upon any principle save that the high flight is the 

 less fatiguing. Even rooks may be observed to ad- 

 just the height of their daily excursions from the 

 rookeries, to the distance at which the pasture upon 

 which they are to feed lies ; and the swallow tribe 

 wheel about far more rapidly and gracefully when 



so, after months of labour, he produced a pair of ! they hawk high before rain, than when they skim 

 wings, and, mounting the top of a high barn at his the surfaces of the pools in fine weather. If we may 

 father's farm-yard, spread them for flight, and shot ! judge from their appearance when we see them on 

 boldly into the air ; but no shot pigeon, or even pig the wing (the only means we have of judging), it 

 of lead, was ever more true to the perpendicular ; and 



it was well for his bones that the cess pool of the 

 farm-yard received him on its soft bosom ; for the 

 wings barely saved him, till he could begot out, from 

 the triple death of being drowned, smothered, and 

 " sconfassed" (that word is untranslatable) in the 

 savoury compost. The consequence of this attempt 

 at flight was not only the loss of all the high repu- 

 tation which the party had previously enjoyed, but 

 so overwhelming a burden of ridicule that it broke 

 his spirit, and he became literally good for nothing 

 while he lived. 



The cases of all who attempt flying by mechanical 

 contrivances may not be quite so disastrous as this 

 one, but they must be all equally unsuccessful. Nor 

 does it appear that the guiding of a balloon, in any 

 other direction than that in which the current of the 

 air happens to drive it, can be more successful. 

 There is no fulcrum from which a purchase can be 

 obtained but the air itself; and the air presses equally 

 in all directions when still, and in the direction of 

 the wind with a force proportional to the velocity of 

 that when it blows. 



Still the bird, when it flies, overcomes mechanical 

 resistances, and, according to the general law of 

 matter, it must overcome them by mechanical means. 

 The bird, too, is very simple in its form, and certainly 



appears that birds, when they are not in search of 

 any thing upon the ground near them, mount up till 

 they come to that density of atmosphere which is 

 best suited to their weight and wings, and then con- 

 tinue onwards. There maybe another reason : those 

 upper regions to which the birds ascend on their 

 long flights are in a great measure exempted from 

 the momentary gusts and squalls which war upon 

 the surface under them. 



This buoyancy, arising from the structure of the 

 wings, is a very beautiful portion of the mechanics of 

 birds, but it is one which man would find it very 

 difficult to imitate. The general form of the wing, 

 the characters of the feathers, the articulations of all 

 the joints, the relative power of the muscles, and even 

 the general form and action of the whole body, are 

 concerned in it. They are all living too all exerting 

 their peculiar animal actions, in unbidden harmony, 

 with each other ; for even the feathers are alive, and 

 the skin in which they are inserted can communicate 

 an individual motion to each. Thus the process is 

 one which we cannot analyse so as to bring it within 

 the scope of our very limited notions of mechanics, 

 though there is no doubt that both the compound 

 motion, and all the individual motions, of which it is 

 made up, are in strict accordance with mechanical 

 principles. 



