SO A HISTORY OF 



contracted ; so that the animal rises by the impulse, till it spieaus tlifc 

 wing for a second blow. For this reason, we always see bird* choose 

 to rise against the wind, because they have thus a greater body of air 

 on the under than the upper side of the wing. For these reasons, also, 

 large fowls do not rise easily ; both because they have not sufficient 

 room at first for the motion of their wings, and because the body of 

 air does not lie so directly under the wing as they rise. 



In order to move the wings, all birds are furnished with two very 

 strong pectoral muscles, which lie on each side of the breast-bone 

 The pectoral muscles of quadrupeds, are trifling in comparison to 

 those of birds. In quadrupeds, as well as in man, the muscles which 

 move the thighs and hinder parts of the body, are by far the strongest, 

 while those of the arms are feeble ; but in birds, which make use of 

 their wings, the contrary obtains ; the pectoral muscles, that move 

 the wings or arms, are of enormous strength, while those of the thighs 

 are weak and slender. By means of these, a bird can move its wings 

 with a degree of strength which, when compared to the animal's size, 

 is almost incredible. The flap of a swan's wing would break a man's leg ; 

 and a similar blow from that of an eagle has been known to lay a man 

 dead in an instant. Such, consequently, is the force of the wing, and 

 such its lightness, as to be inimitable by art. No machines that human 

 skill can contrive, are capable of giving such force to so light an ap- 

 paratus. The art of flying, therefore, that has so often and so fruit- 

 lessly been sought after, must, it is feared, for ever be unattainable ; 

 since, as man increases the force of his flying machine, he must be 

 obliged to increase its weight also. 



In all birds, except nocturnal ones, the head is smaller, and bears 

 less proportion to the body than in quadrupeds, that it may more rea- 

 dily divide the air in flying, and make way for the body, so as to ren- 

 der its passage more easy. Their eyes also are more flat and depressed 

 than in quadrupeds ; a circle of small plates of bones, placed scalewise, 

 under the outer coat of the organ, encompasses the pupil on each, to 

 strengthen and defend it from injuries. Besides this, birds have a kind 

 of skin, called the nictitating membrane, with which, like a veil, they 

 can at pleasure cover their eyes, though their eye-lids continue open. 

 This membrane takes its rise from the greater or more obtuse corner 

 of the eye, and serves to wipe, cleanse, and probably to moisten its 

 surface. The eyes, though they outwardly appear but small, yet sepa- 

 rately, each almost equals the brain ; whereas in man the brain is more 

 than twenty times larger than the orbit of the eye. Nor is this organ 

 in birds less adapted for vision by a particular expansion of the optic 

 nerve, which renders the impressions of external objects more vivid 

 and distinct. 



From this conformation of the eye, it follows, that the sense of see- 

 Ing in birds is infinitely superior to that of other animals. Indeed this 

 piercing sight seems necessary to the creature's support and safety. 

 Were this organ blunter, from the rapidity of the bird's motion, it 

 would be apt to strike against every object in its way; and it could 

 scarcely find subsistence, unless possessed of a power to discern its 

 food from above with astonishing sagacity. A hawk, for instance; 

 perceives a lark at a distance which neither men nor dogs could spy ; 



