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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 foil 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 5 expressly expressly intended. Two points are manisest: 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, would always live in daylight. An animal, which, though made for action, and delighting in action, must have its strength repaired by sleep, meets by its constitution the returns of day and night. In the human species for instance, were the bustle, the labour, the motion of life, upheld by the constant presence of light, sleep could not be enjoyed without being disturbed by noise, and without expence of that time, which the eagerness of private interest would not contentedly resign. It is happy therefore for this part of the creation, I mean that it is conformable to the frame and wants of their constitution, that nature, by the very disposition of her elements, has commanded, as it were, and imposed upon them, at moderate intervals, a general intermission of their toils, their occupations, and pursuits.
But it is not for man, either solely or principally, that .night is made. Inserior, but less perverted natures, taste its solace, and expect its return, with greater exactness and advantage than he does, I have often observed, and never observed but to admire, the fatisfaction no less than the regularity, with which the greatest part of the irrational world yield to this soft necessity, this grateful vicissitude; how comfortably, the birds of the air, for example, address themselves to the repose of the evening; with what alertness they resume the activity of the day.
Nor does it disturb our argument to congress, that certain species of animals are in motion during the night, and at rest in the day. With respect even to them it is still true, that there is a change of condition in the animal, and an external change corresponding with it. There is still the relation, though inverted. The fact is, that the repose of other animals sets these at liberty, and invites them to their food or their sport, •
If the relation of Jleep to night', and, in some instances, its converse, be real, we cannot reflect without amazement upon the extent to which it carries us. Day and night are things
Y close close to us: the change applies immediately to our sensations: of all the phenomena of nature, it is the most familiar to our experience: but, in its cause, it belongs to the great motions which are pasting in the heavens. Whilst the earth glides round her axle, she ministers to the alternate necessities 'of the animals dwelling upon her surface, at the fame time that the obeys the influence of those attractions which regulate the order of many thoufand worlds. The relation therefore of sleep to night, is the relation of the inhabitants of the earth to the rotation of their globe; probably it is more: it is a relation to the system, of which that globe is a part; and, still further, to the congregation of systems, of which theirs is only one- If this account be true, it connects the meanest individual with the universe itself j a chicken roosting upon its perch, with the spheres re volving in the firmament.
But if any one object to our representation, that the succession of day and night, or the rotation of the earth upon which it depends, is not refolvible into central attraction, we will refer him to that which certainly is,—to the change of the seasons. Now the constitu:. 1 tion tion of animals susceptible of torpor, bears a relation to winter, similar to that which sleep bears to night. Against not only the cold, but the want of food, which the approach of winter induces, the preserver of the world has provided, in many animals by migration, in many others by torpor. As one example out of a thousand, the bat, if it did not sleep through the winter, must have starved, as the moths and flying insects, upon which it seeds, difappear. But the transition from summer to winter carries us into the very midst of physical astronomy, that is to fay, into the midst of those laws-which govern the solar system at least, and probably all the heavenly bodies.