ances of small animals exceed those of the larger in proportion to their size. Thus the kangaroo, a tolerably large animal weighing about as much as a sheep, can leap about twenty feet, between three and four times its length, whilst the jerboa, a native of Canada, a very small animal, leaps fifty times its length. This seems at first very remarkable, yet it is in strict accordance with the laws of mechanics. The objects of this are pretty clear. It gives the smaller species a fair chance of escaping from the larger; besides, as the texture of their parts does not increase in strength and power of resistance in proportion to their size, the larger animals would be destroyed by the concussion, were they capable of exertions proportioned to those of the smaller. For the same reason, small animals can fall a much greater distance than the larger in proportion to their size; indeed, absolutely a much greater distance. A mouse, a squirrel, or a cat may fall fifteen or twenty feet and escape without harm, whilst a horse, an ox, or an elephant would be irreparably maimed.

Birds have at once great disposition and great power for motion. The ostrich, in whom the amount of muscle, which in other birds is appropriated to the movements of the wings, is transferred to the legs, is the most rapid of all animals on foot, easily distancing the fleetest Arabian horses. But it is in the flight of birds that we find the most wonderful exhibitions of speed. The common crow can accomplish twenty-five miles an hour, but it is one of the slowest of birds. The flight of the eider-duck has been found to average ninety miles, the swallow a little more, but the swift two hundred and seventy; and these birds will pass the greater part of the daylight upon the wing. Hawks fly at the rate of one hundred and fifty miles, and eagles not much, if any, less. Several facts are historically recorded, which show that these estimates are not probably exaggerated. A falcon, belonging to Henry IV. of France, escaped from Fontainebleau, and was found, twenty-four hours afterward, at Malta, one thousand three hundred and fifty miles distant. This would give fifty-seven miles an hour, supposing it to have been all the time upon the wing; which is not likely, so that its speed was not probably less than from seventy-five to one hundred miles while in mo

tion. A canary bird has been known to fly from Andalusia to the island of Teneriffe in sixteen hours, the distance being about eight hundred miles. Birds have been killed in the northern States of the Union, in whose crops was found rice undigested which must have been eaten in the rice-fields of Carolina.

Of the rate at which the swimming Mammalia and Fishes move, we know much less. It is greater than that of quadrupeds, but less than that of birds. Boats and sailing vessels rarely exceed ten or twelve miles an hour, but whales and porpoises pass by them when under full sail with apparent ease. There is reason to believe that true fishes move more rapidly than this. The speed of a whale is probably not less than twenty miles an hour, and the fish which migrate in shoals go at least as rapidly.

Some animals possess a capacity for motion dependent upon a power of suction that enables them to attach themselves closely to objects upon which or over which they wish to move. Many insects are able, probably by this provision, to walk along perpendicular walls, or even the ceilings of rooms, as the common house-fly. A structure for this purpose has been supposed to exist in the walrus and seal, by means of which they are able to crawl up the sides of smooth rocks or pieces of ice, and also to make an opening from beneath upward, through an expanse of ice.

A species of lizard in the East moves about like an insect, and adheres to perpendicular and inverted surfaces with great tenacity. Its feet have been found provided with a great number of cavities, which act like cupping-glasses and fit them to the smoothest surfaces. A kind of fish, called the remora, has upon the top of its head a large surface endowed with this power. Being naturally of a slow and indolent habit, it thus attaches itself to the bodies of other fish, or to the bottoms of vessels, and is thus transported from place to place. So aware is it of its necessities that, when once attached, it cannot be induced by the most tempting bait to quit its hold till the end of its journey. It was an ancient belief that this fish had the power of impeding or even arresting the progress of the vessel to which it was attached, and to this was once attributed the loss of the battle of Actium.

There is no class of animals which present the phenomena of motion in so varied and remarkable a manner as Insects. They, indeed, combine the powers of all the other classes, sometimes even in the same individual at different stages of its existence. They walk, run, jump, and burrow with the quadruped. They fly with the bird. They glide or crawl with the serpent. They swim with the fish. The locust by the help of its wings leaps two hundred times its own length, and the flea without them a corresponding distance. The froghopper exceeds this by one quarter, leaping two hundred and fifty times its length. There is a kind of spider which spins no web to entangle its prey, but secures it by leaping upon it, which it can do even sideways. It has been seen to jump two feet upon a humblebee.

Their rapidity of motion in flight is not less remarkable, and some species can fly in all directions without turning. Leuwenhoek once watched a swallow chasing an insect in an inclosure a hundred feet long. The little creature flew with such astonishing velocity, to the right, to the left, upward, and downward, that the bird, remarkable not only for the rapidity of its flight but the quickness of its evolutions, was foiled in all its attempts to seize it. Many insects that live but for a short time in the winged state, pass almost the whole of this period upon the wing. It has been calculated that, in its ordinary flight, the house-fly makes six hundred strokes with its wings which carry it five feet in the second; but when alarmed its velocity is so increased, that it has been calculated to make four thousand strokes and pass over thirty-five feet in the same time.

car.

The rapidity and adroitness of these animals is in no way more familiarly illustrated than by observing them in a railroad When travelling at the rate of thirty or even forty and fifty miles an hour, they move about from place to place, backward, forward, upward, and downward, exactly as if the vehicle. were at rest. Yet in this case their motions must be most nicely adapted with reference to the places on which they alight and the direction in which they fly.

The speed at which some of them run is not less worthy of notice. We are told of a fly, so minute as to be scarcely visible, which can run six inches a second, making in that time ono

thousand and eighty steps. They climb also in various ways and with great skill; some by claws which lay hold on irregularities in the surface of bodies, some by means of soft cushions formed of dense hairs which line the under part of their limbs, some by suction, and others by means of a tenacious fluid which enables them to adhere against the force of gravity.

Insects also swim and dive. Some of them swim by the help of broad, flat hind legs, acting like paddles; others have a fringe of hairs placed in a suitable position to answer the same purpose. Some swim or float along upon the back, whilst others skate, or run upon the surface of the water.

They burrow as the mole does, principally by the head and fore legs where substances are soft, or by the aid of the jaws where they are hard. Many species in this way provide themselves with habitations: ants in the earth, many wasps in wood, and the house cricket in mortar. They bore also in search of food, and to provide a suitable place for depositing their eggs.

Some of the motions of other classes present a striking contrast in their sluggishness and drowsiness with those observed in Insects; so much so that it is not an uncommon notion, that both the fresh and salt water mussels have not the locomotive faculty. But this is a vulgar error. It is almost unnecessary to mention that the exterior part of mussels consists of two shells hinged together, which the animals can open or shut at pleasure. Every person must likewise have observed, in the structure of the animal itself, a fleshy protuberance of a much redder color, and denser consistence, than the other parts of the body. This muscular protuberance, which consists of two lobes, has been denominated a trunk or tongue; but it is an instrument by which the creature is enabled to perform a progressive though a very slow motion; and, therefore, in describing its manner of moving, I shall call these two lobes the animal's tentacula or feet.

'When inclined to remove from its present situation, the river mussel opens its shell, thrusts out its tentacula, and, while lying on its side in a horizontal position, digs a small furrow in the sand. Into this furrow, by the operation of the same tentacula, the ani

mal makes the shell fall, and thus brings it into a vertical position. We have now got our mussel on end; but how is he to proceed? He stretches forward his tentacula, by which he throws back the sand, lengthens the furrow, and this fulcrum enables him to proceed on his journey.'

CHAPTER V. (W.)

VOICE OF ANIMALS AND THEIR MODES OF COMMUNICATION.

As the existence of sight implies objects to be seen, the existence of hearing implies sounds to be heard. Nature is full of these. To man all of them are more or less significant, and are the objects of his attention; that of other animals is chiefly enrossed by those that serve to warn them of danger, to direct them to their food, or to establish an intercourse with others of their own species.

Voice, in its proper sense, is confined to those animals that breathe air through a windpipe by means of lungs. Hence it belongs only to the vertebral animals of the first three classes, Mammalia, Birds, and Reptiles. The air entering the lungs for the purposes of respiration is, in its passage, chiefly in expiration,made to vibrate by an apparatus provided for the purpose, which gives origin to sound. This apparatus, called the larynx, is, in man and quadrupeds, placed at the top of the windpipe. In birds it is situated lower down, where the canal divides to pass to the lungs. The structure of these organs is too complicated to be made intelligible in all their details without actual inspection of the parts themselves. It is sufficient here to say that the principle upon which vibration takes place is the same as that upon which it depends in some wind-instruments, as the hautboy and the clarinet, but modified so as to produce variations far more delicate.

The possession of voice does not imply the use of words, but