those plants that are cultivated by the farmer and the gardener, for the use of man. All the cereal, leguminous, potato, and cabbage tribes are of this kind, and seem to be intended, along with many other means in the economy of Providence, to verify the sentence so early pronounced on our sinning race, that in the sweat of their face they must eat bread. It is, indeed, in this view, a most remarkable provision, that, while the means of subsistence are so amply provided for the lower animals, man is left to procure his food by the exercise of his own mental and bodily powers, in the labors of cultivation ; and, for this purpose, finds it necessary to counteract the natural tendencies of vegetation, as well as to control the habits, and subdue the propensities of the brute creation.

Among animals, the balance which we have been considering, is kept up in a way different from that which takes place in the vegetable kingdom, though in some respects analogous to it. Here, too, the powers of reproduction are with obvious design unequally distributed, being most copiously bestowed on those species which are either most useful to man, or most harmless in their own nature, or least capable of defending themselves. Were not this the case, animals of prey, whose species are numerous, and are to be found in all the classes of animated nature, from the lowest to the highest, would soon destroy the more helpless kinds, and reduce the various orders of beings to a few of nearly equal strength and prowess in the various genera. Among beasts, the lion and tiger, for example, would desolate the tropical regions; the wolf would reign paramount in the temperate zone; and the arctic bear would overrun the regions bordering on the poles, till nothing would be left for them to devour but creatures of their own species. Among birds, the eagle, the vulture, and the condor, would each assert the terrible powers of its nature, till the other feathered tribes, in their respective localities, had been exterminated; and as to fishes, the enormous whale,* and the

*The Greenland whale is supposed to live only on medusæ or shrimps; but the cachalot, [or spermaceti whale,] and its varieties, are exceedingly voracious.

rapacious shark, each of which devours the inferior tribes by hundreds at a mouthful, would quickly divide the desolated ocean between them.

The very fact, therefore, that, notwithstanding the existence of such formidable enemies, the other tribes of animated beings not only survive, but abound, is a proof that the Author of Nature has provided sufficient checks to their power and rapacity. Of quadrupeds alone, from 800 to 1000 species are known to exist; and, as we descend in the scale to the lower genera, their species proportionally increase, till among the insect and microscopic tribes, they become almost innumerable. If this be the case with regard to species, how would the mind be overwhelmed with the immensity of the subject, were it to attempt to estimate the number of individual existences in the animal and vegetable kingdoms. Let us recognise and admire the Designing Mind which has with such wonderful skill adjusted the balance of nature, and fitted it to the condition of man in his present state. It is impossible not to be struck with the analogy which runs through all the departments of organized existence, from the highest to the lowest, in this as well as in other instances. We see every where a superabundant power of reproduction counteracted and balanced, by what may be justly called antagonist powers. Among these opposing forces, we find voracity and famine every where, excessive heat, and periodical storms, in tropical countries, excessive cold during the winter of the temperate and frigid regions, each in its own manner and its own place, doing the necessary work of destruction.

THIRD WEEK-THURSDAY.

ALTERNATION OF DAY AND NIGHT.

THE SUN now remains but a short period above the horizon; and, even during that short period, the comparative

He is

intensity of his light and heat is much decreased. daily taking a less extensive circuit in our heavens ; and in another month the length of the day will be diminished by more than another hour. Were the influence of the

sun, and the length of the day, to continue in this state, the whole organized world, in the climate which we inhabit, would quickly be destroyed. But the year will soon recommence its annual round; and nature is even now preparing for its coming labors.

The repose of plants, and even of many animals, in this dreary season, reminds us of the salutary provision, of a similar description, which is made for the diurnal recruiting of exhausted strength by the alternation of night with day. That this arrangement is adapted to the constitution of animal and vegetable existences, will be readily admitted; and, on examining particulars, we shall be confirmed in our general conclusion. It is not merely true, that nature requires a frequently recurring period of rest, but that the actual period of twenty-four hours, divided between activity and repose, is the best suited for this end. If this be so, it implies a Designing Cause; for such a period is arbitrary; that is to say, no reason can be assigned, in the nature of things, either why the earth should complete her daily revolution in twenty-four hours, or why animals and vegetables should require a season of rest in that precise interval. As to the former, no mechanical or physical necessity requires, that our earth should complete three hundred and sixty-five revolutions in a year. It might, apparently, move either faster or slower, without the slightest inconvenience to the system with which it is connected. Jupiter and Saturn revolve on their axes each in ten hours, which, considering their bulk, must carry their equators round with a velocity immensely greater than that of the earth, while Mercury, which is so much nearer the sun, and so much smaller, has its day and night nearly of the same length as our

own.

Now, if we look at the vegetable world, we shall find, as already observed, a remarkable adaptation of this arbitrary period of twenty-four hours to the constitution of

I.

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VII.

its various productions. In some plants, indeed, this is not so obvious; but there are others, which clearly show that they are endowed with a periodical character, corresponding with the average length of our day. Linnæus classified a number of plants according to their time of opening and shutting, with reference to the hour of the day, and found, that there are some which change their. hour of opening and shutting as the day becomes longer and shorter, while there are others which do not seem to be affected by the actual state of the light and heat, but have a daily period of their own, independent of these influences, expanding their leaves, and closing them, at a particular hour, whatever be the state of the weather, or the length of the day. Both of these instances prove an adaptation to the diurnal revolution of the earth, which could not be the effect of chance, and must, therefore, have been the work of an Intelligent Cause.

This adjustment, is still more remarkable in the animal world. A period of sleep is necessary for the health and vigor of living beings; and the alternation of day and night, which actually takes place, seems, from various considerations, to be that which is best fitted for them; or, at all events, any very great deviation from the arrangement actually established, would be prejudicial. When a workman retires from his twelve hours' labor, he is sufficiently inclined to take rest; and, although it is possible for him to encroach on the night, without much inconvenience, and to extend his exertions, if not immoderate, to fifteen or sixteen hours, a longer period, without an interval of repose, would incur the risk of undermining the constitution. It is certain, at least, that a considerable proportion of time, spent in sleep, during the four and twenty hours, is of importance to the health, both of body and mind; and that, if our day were extended, for example, to the length of two, the human powers would droop under the prolonged period which would thus occur between the intervals of rest.

To the lower animals, also, the alternation of day and night, as it actually exists, is wisely adapted. To some of these, the day is the season of collecting their food;

to others, the night: but, whatever be the instincts which guide them in this respect, we cannot but perceive that the adjustment between their constitution and habits, on the one hand, and the period of light and darkness on the other, is such, as to show that the one bears reference to the other, and to indicate benevolent contrivance.

It is no valid objection to this view, that the relative length of the days and nights vary, very considerably in our climate, and still more in higher latitudes; because, where this is the case, we find adaptations and adjustments of a different kind, which, in some degree, compensate for these variations; and because, except in regions approaching very near the poles, the revolution of day and night is uniformly comprised in twenty-four hours; and the only difference consists in a longer or shorter time, during which the curtains of night are drawn,—an inconvenience which the ingenuity of man removes by artificial means, and to which, the habits and wants of the lower animals, and of plants, are wonderfully accommodated.

On the whole, we have here another proof of an Intelligent Creator, who has suited the organized beings he has called into existence, to the circumstances of the material world, in which he has been pleased to place them. The observations of Mr. Whewell on this subject, to whose judicious statements we have so frequently had occasion to refer, are entirely to the purpose. The hours of food and repose," says he, "are capable of such wide modifications, in animals, and, above all, in man, by the influence of external stimulants and internal emotions, that it is not easy to distinguish what portion of the tendency to such alternations depends on original constitution. Yet, no one can doubt that the inclination of food and sleep is periodical, or can maintain, with any plausibility, that the period may be lengthened or shortened without limit. We may be tolerably certain, that a constantly recurring period of forty-eight hours, would be too long for one day of employment, and one period of sleep, with our present faculties; and all, whose bodies and minds are tolerably active, will probably agree, that, in