But if the individual itself remain unchanged under every possible variation, how are we to conceive that a change in this respect can affect the progeny? Can any one believe that if a greyhound bitch, while with young, were allowed to bring forth. her litter in one place (in Britain suppose, the place of her nativity,) she would produce true greyhounds, but if she were carried to Norway, the litter would turn out to be mastiffs; in Turkey longhaired pointers; and in other countries hounds, terriers, and all the other varieties of dogs? At the bare mention of such a position the mind revolts from it, as from a self-evident absurdity: but if the litter were not brought forth in these states in different climates, the puppies must be changed instantaneously after they come into the world; for, as we have seen, they are not changed by it at any other period of their life, it must be now that the change is effected, (like tadpoles into frogs,) or never. But who has ever heard of such a metamorphoses? We all know that no such thing takes place. Yet this, and more, must have happened were there the smallest foundation for this hypothesis. These changes must have happened not once only, but often; not casually, but invariably; of course it would have been utterly impossible to propagate a greyhound in one country, or a beagle in the other; in short, every country would have had its own particular variety of dogs, and none other. But this we know is contradicted by the clearest facts, and the universal experience of man

kind; and it must appear to be not a little surprising to those who reflect upon it, that an hypothesis which is, under every point of view, so absurd, should ever have obtained currency for one moment among men who had their eyes open, and were not deprived of the power of reasoning.

CHAP. VII.

BIRDS.

"But who the various nations can declare,
That plough with busy wing the peopled air?
These cleave the crumbling bark for insect food;
Those dip the crooked beak in kindred blood;
Some haunt the rushy moor, the lonely woods;
Some bathe their silver plumage in the floods."

THE Ostrich, the Emu, and the Cassowary, are not only remarkable, by reason of their superiority of size, but seem to claim our first attention among the feathery tribes, on account of their constituting some of those apparent links, by which the winged tribe is united to the order of Quadrupeds. For although these animals resemble birds in the outline, and in several parts of their conformation, they certainly cannot be classed among the more perfect orders of the species, in as much as they do not make use of their wings for the purpose of flying; and as to internal formation, the Ostrich is said to have as great a resemblance to the four-footed as to the volatile. order.

The structure of these creatures, as well as their appetites, is however well adapted for the situations in which they are severally placed, and they appear to know well how to supply the defect of some of their members by the use which they make of others.

Of all animals that move on their legs, the Ostrich is by far the swiftest; and although the Arabians train their fleetest horses for the chase, it is not likely they would be successful in the pursuit of this animal, were it not for his circling manner of running. Nor is this surprising, when we consider that this lofty mass of light materials is not only carried forward by his long springing legs, but is impelled along by his wings, which he keeps in constant motion, and apparently serve the purpose of

oars.

The Emu, or Ostrich of the new continent, is also a remarkably swift runner, but its manner of assisting its legs is somewhat different from the former; besides making use of something behind, like a heel, to push it forward, this animal uses a kind of action peculiar to itself, first lifting up one wing and keeping it elevated for some time in form of a sail, then letting it drop and elevating the other; by this means it moves along with such rapidity, that even the Greyhound can seldom overtake it. The favourite climate of the Cassowary seems to begin where that of the Ostrich terminates, in the old world; and although its wings are so very small, that being covered with the hair on the back they are scarcely perceptible, it kicks up behind with the

one leg, and then making a bound forward with the other, proceeds with such amazing speed, that the swiftest racer would be unable to maintain the pursuit!

In the structure of Birds of the more perfect order, a few things demand our most serious attention:

The whole body is shaped in the most convenient manner for making their way through the air; being, as Mr. Ray observes, constructed very near Sir Isaac Newton's form of least resistance, According to Bar, in his continuation of Buffon, " It is neither extremely massive nor equally substantial in all its parts; but, being designed to rise in the air, is capable of expanding a large surface without solidity. The body is sharp before, to pierce and make its way through that element; it then gradually increases in bulk, till it has acquired its just dimensions, and falls off in an expansive tail."

The motion of this order being two-fold, walking and flying, they are provided with legs at once wonderfully contrived to walk with, and raise them like a spring for their flight; wings to buoy them up and waft them along; and a tail to keep them steady in the air, assist them in their evolutions, and to direct their course.

Although their feathery covering is admirably constructed for lightness and buoyancy, their wings are furnished with a strength that is amazing; so that the flap of a Swan's wing has been known to break a man's leg; and a similar blow from an Eagle has produced instant death; and by these they

are enabled to impel themselves forward with a rapidity that exceeds the fleetest quadruped. To fit them the better for their flight, the feathers are disposed in the most perfect order, lying one way; and that they may glide more smoothly along, they are furnished with a gland situated on the rump, from which they occasionally press out oil with the bill, and anoint the feathers. In water-fowl this oil is so plentiful, that by it their plumage is rendered completely water-proof.

The beak, or bill of birds, is a curious piece of art, formed of a hard horny substance, constructed in the most commodious manner for piercing the air. Their ears stand not out from their head to retard their flight, while their eyes are placed in such situations as to take in nearly a hemisphere on either side.

Birds have no teeth to chew their food; but those of the granivorous kind are provided with two stomachs; in one of which the victuals are softened and macerated before they enter the other to be completely digested. Being often employed in traversing the upper regions, where they behoved to be much incommoded did they bring forth their young in the manner of quadrupeds, their manner of generating is wisely made to differ, and their offspring are produced by means of eggs. In the speedy growth of young birds, by which they acquire a degree of strength and size to be able so soon to provide for themselves, we have also an instance of the tender care of Providence.