We have already considered relation, and under different views; but it was the relation of parts to parts, of the parts of an animal to other parts of the same animal, or of another individual of the same species.

But the bodies of animals hold, in their constitution and properties, a close and important relation to natures altogether external to their own; to inanimate substances, and to the specific qualities of these, e. g. they hold a strict relation to the ELEMENTS by which they are surrounded.

I. Can it be doubted, whether the wings of birds bear a relation to air, and the fins of fish to water? They are instruments of motion, severally suited to the properties of the medium in which the motion is to be

performed : which properties are different. Was not this difference contemplated, when the instruments were differently constituted ?

II. The structure of the animal ear depends for its use not simply upon being surrounded

by a fluid, but upon the specific nature of that fluid. Every fluid would not serve: its particles must repel one another; it must form an elastic medium : for it is by the successive pulses of such a medium, that the undulations excited by the surrounding body are carried to the organ ; that a communication is formed between the object and the sense ; which must be done, before the internal machinery of the ear, subtile as it is, can act at all.

III. The organs of voice, and respiration, are, no less than the ear, indebted, for the success of their operation, to the peculiar qualities of the fluid, in which the animal is immersed. They, therefore, as well as the ear, are constituted upon the supposition of such a fluid, i. e. of a fluid with such particular properties, being always present. Change the properties of the fluid, and the organ cannot act; change the

and the

properties of the Auid would be lost. The structure therefore of our organs, and the properties of our atmosphere, are made for one another. Nor does it alter the relation, whether

you allege the organ to be made for the element (which seems the most natural way of considering it), or the element as prepared for the organ.

IV. But there is another fluid with which we have to do ; with properties of its own; with laws of acting, and of being acted upon, totally different from those of air and water : and that is light. To this new, this singular element; to qualities perfectly peculiar, perfectly distinct and remote from the qualities of any

other substance with which we are acquainted, an organ is adapted, an instrument is correctly adjusted, not less peculiar amongst the parts of the body, not less singular in its form, and in the substance of which it is composed, not less remote from the-materials, the model, and the analogy of any other part of the animal frame, than the element to which it relates, is specific amidst the substances with which we converse. If this does not prove appropriation, I desire to know what would prove it.

Yet the element of light and the organ of vision, however related in their office and use, have no connexion whatever in their original. The action of rays of light upon the surfaces of animals, has no tendency to breed eyes

in their heads. The sun might shine for ever upon living bodies without the smallest approach towards producing the sense of sight. On the other hand also, the animal eye does not generate or emit light.

V. Throughout the universe there is a wonderful proportioning of one thing to another. The size of animals, of the human animal especially, when considered with respect to other animals, or to the plants which grow around him, is such, as a regard to his conveniency would have pointed out. A giant or a pygmy could not have milked goats, Țeaped corn, or mowed grass ; we may add, could not have rode a horse, trained a vine, shorn a sheep, with the same bodily ease as we do, if at all. A pygmy would have been lost amongst rushes, or carried off by birds of prey.

It may be mentioned likewise, that the model and the materials of the human body being what they are, a much greater bulk would have broken down by its own weight. The persons of men who much exceed the ordinary stature, betray this tendency.

VI. Again (and which includes a vast variety of particulars, and those of the greatest importance); how close is the suitableness

of the earth and sea to their several inhabitants; and of these inhabitants, to the places of their appointed residence !

Take the earth as it is; and consider the correspondency of the powers of its inhabitants with the properties and condition of

the soil which they tread. Take the inhabitants as they are; and consider the substances which the earth yields for their use. They can scratch its surface; and its surface supplies all which they want. This is the length of their faculties: and such is the constitution of the globe, and their own, that this is sufficient for all their occasions.

When we pass from the earth to the sea, from land to water, we pass through a great change: but an adequate change accompanies us, of animal forms and functions, of animal capacities and wants; so that correspondency remains. The earth in its nature is very different from the sea, and the sea from the earth: but one accords with its inhabitants, as exactly as the other.

VII. The last relation of this kind which I shall mention, is that of sleep to night: and it appears to me to be a relation which was expressly intended.

Two points are manifest; first, that the animal frame requires sleep ; secondly, that night brings with it a silence, and a cessation of activity, which allows of sleep being taken without interruption, and without loss.

Animal existence is made up of action and slumber; nature has provided a season for each. An animal, which stood not in need of rest,

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