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It may be mentioned likewife, 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 perfons of men, who much exceed the ordinary ftature, betray this tendency.

VI. Again; and which includes a vast variety of particulars, and thofe of the greatest importance, how clofe is the fuitableness of the earth and fea to their feveral inhabitants; and of thefe inhabitants to the places of their appointed refidence ?

Take the earth as it is; and confider the corre fpondency of the powers of its inhabitants with the properties and condition of the foil which they tread. Take the inhabitants as they are; and confider the fubftances which the earth yields for their use. They can feratch its furface, and its furface fupplies all which they want. This is the length of their faculties; and fuch is the conftitution of the globe, and their own, that this is fufficient for all their occafions.

When we pass from the earth to the fea, from land to water, we país through a great change; but an adequate change accompanies us of animal forms and functions, of animal capacities and wants, fo that correfpondency remains. The earth in its nature is very

different from the fea, and the fea from the earth; but one accords with its inhabitants, as exactly as the other.

VII. The laft relation of this kind which I fhall mention is that of fleep to night. And it appears to me to be a relation which was exprefsly intended. Two points are manifeft: firft, that the animal frame requires fleep; fecondly, that night brings with it a filence, and a ceffation of activity, which allows of fleep being taken without interruption, and without lofs. Aniinal exiflence is made up of action and flumber nature has provided for each. An animal, which flood not in need of reft, would always live in

day-light. An animal, which, though made for action, and delighting in action, muft have its ftrength repaired by fleep, meets by its conftitution the returns of day and night. In the human fpecies, for inftance, were the buffle, the labour, the motion of life, upheld by the conftant prefence of light, fleep could not be enjoyed without being difturbed by noife, and without expence of that time, which the eagernefs of private intereft would not contentedly refign. It is happy therefore for this part of the creation, I mean that it is conformable to the frame and wants of their conftitution, that nature, by the very difpofition of her elements, has commanded, as it were, and impofed upon them, at moderate intervals, a general intermiflion of their toils, their occupations, and purfuits.

But it is not for man, either folely or principally, that night is made. Inferior, but lefs perverted natures, tafte its folace, and expect its return, with greater exactness and advantage than he does. I have often obferved, and never obferved but to admire, the fatisfaction no less than the regularity, with which the greatest part of the irrational world yield to this foft. neceffity, this grateful viciffitude; how comfortably, the birds of the air, for example, addrefs themselves to the repose of the evening; with what alertnefs they refume the activity of the day.

Nor does it difturb our argument to confefs, that certain fpecies of animals are in motion during the night, and at reft in the day. With refpect even to them it is ftill true, that there is a change of condition in the animal, and an external change correfponding with it. There is ftill the relation, though inverted. The fact is, that the repofe of other animals fets these at liberty, and invites them to their food or their sport.

If the relation of fleep to night, and, in fome inftances, its converfe, be real, we cannot reflect with

out amazement upon the extent to which it carries us. Day and night are things clofe to us: the change applies immediately to our fenfations of all the phanomena of nature, it is the most familiar to our experience but, in its caufe, it belongs to the great motions which are paffing in the heavens. Whilft the earth glides round her axle, fhe minifters to the alternate neceffities of the animals dwelling upon her furface, at the fame time that fhe obeys the influence of those attractions, which regulate the order of many thousand worlds. The relation therefore of fleep 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 fyftem, of which that globe is a part; and, ftill further, to the congregation of fyftems, of which theirs is only one. If this account be true, it connects the meaneft individual with the universe itfelf; a chicken roofling upon its perch, with the fpheres revolving in the firmament.

But if any one object to our reprefentation, that the fucceffion 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 feafons. Now the conftitution of animals fufceptible of torpor, bears a relation to winter, fimilar to that which fleep bears to night. Against not only the cold, but the want of food, which the approach of winter induces, the preferver of the world has provided, in many animals by migration, in many others by toi por. As one example out of a thoufand, the bat, if it did not fleep through the winter, muft have ftarved, as the moths and flying infects, upon which it feeds, disappear. But the tranfition from fummer to winter carries us into the very midft of phyfical aftronomy, that is to fay, into the midft of thofe laws which govern the folar fyftem at least, and probably all the heavenly bodies.

CHAPTER XVIII.

INSTINCTS.

THE order may not be very obvious, by which I place inftincts next to relations. But I confider them as a fpecies of relation. They contribute, along with the animal organization, to a joint effect, in which view they are related to that organization. In many cafes they refer from one animal to another animal'; and, when this is the cafe, become strictly relations in a second point of view.

An INSTINCT is a propenfity, prior to experience, and independent of inftruction. We contend, that it is by instinct that the fexes of animals feek each other; that animals cherifh their offspring; that the young quadruped is directed to the teat of its dam; that birds build their nests, and brood with so much patience upon their eggs; that infects, which do not fit upon their eggs, depofit them in those particular fituations, in which the young, when hatched, find their appropriate food; that it is inftinet, which carries the falmon, and some other fish, out of the fea into rivers, for the purpose of shedding their spawn in fresh water.

We may felect out of this catalogue the incubation of eggs. I entertain no doubt, but that a couple of fparrows hatched in an oven, and kept separate from the rest of their fpecies, would proceed as other fparrows do, in every office which related to the production and preservation of their brood. Affuming this fact, the thing is inexplicable upon any other hypothefis, than that of an instinct, imprefled upon the conftitution of the animal. For, firft, what fhould induce the female bird to prepare a neft before the lays her eggs? It is in vain to fuppofe her to be poffeffed

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of the faculty of reafoning; for no reasoning will reach the cafe. The fullness or diftenfion which the might feel in a particular part of her body, from the growth and folidity of the egg within her, could not poffibly inform her, that he was about to produce fomething, which, when produced, was to be preserved and taken care of. Prior to experience, there was nothing to lead to this inference, or to this fufpicion. The analogy was all againft it; for, in every other inftance, what iffued from the body was caft out and rejected.

But, fecondly, let us fuppofe the egg to be produced into day: How fhould birds know that their eggs contain their young? There is nothing either in the afpect, or in the internal compofition of an egg, which could lead even the moft daring imagination to a conjecture, that it was hereafter to turn out, from under its fhell, a living perfect bird. The form of the egg bears not the rudiments of a resemblance to that of the bird. Infpecting its contents, we find ftill lefs reafon, if poffible, to look for the refult which actually takes place. If we fhould go so far, as, from the appearance of order and diftinction in the difpofition of the liquid fubftances which we noticed in the egg, to guefs that it might be defigned for the abode and nutriment of an animal, (which would be a very bold hypothefis,) we should expect a tadpole dabbling in the flime, much rather than a dry, winged, feathered creature; a compound of parts and properties impoffible to be used in a ftate of confinement in the egg, and bearing no conceivable relation, either in quality or material, to any thing obferved in it. From the white of an egg, would any one look for the feather of a goldfinch? or expect from a fimple uniform mucilage, the most complicated of all machines, the most diversified of all collections of fubftances? Nor would the process of incubation,

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