most curious and peculiar construction, is, beyond all doubt, framed for the express purpose of receiving its impressions. Nothing can be more worthy of observation, than the manner in which the instrument of vision is adapted to the properties of the agent. Light is reflected, in all directions, from every object on which it falls; and, by the construction of a camera obscura, most skilfully contrived, these reflected rays convey form, colour, light, and shade,-a perfect representation, in short, of external objects,-into the interior of the head ; thus, by a mysterious connection between mind and matter, giving rise, in living beings, to the faculty of sight, with all its well known properties and advantages. Who can doubt that there is here a proof of skill and adaptation,that light was made for the eye, and the eye for light?

THIRD WEEK-THURSDAY.

V. THE STARRY HEAVENS.-MOTIONS OF THE PLANETS.

As the fountain of light and heat is placed, by the great Creator, for obviously wise reasons, in the centre of our planetary system, it is natural to expect, that all the arrangements connected with this appointment, should be found so contrived, as to correspond with the beneficent intention; and the more deeply we inquire into the subject, the more distinctly do we observe such an expectation realized. The object of the present paper, will be to illustrate this position, with reference to the motions of the planetary bodies.

And first, with regard to their orbits. We have already stated, that a planet, in its path round the sun, may, according to the laws of motion, describe either an oval or a perfect circle. I have now to observe, that the oval might either be very long or very short, there being, so far as appears, nothing in the mechanical law

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tending to restrict the elliptical form. But it is obvious, that, if the circuit should prove very eccentric, the greatest inconveniences would take place, in a world constituted like ours; and, indeed, a total destruction of animal life would be the necessary consequence; because, at the point of the orbit nearest the sun, the fervour of his rays would be destructive; and, at its greatest distance, his apparent size, and his illuminating and warming power, would diminish together, till the land and the sea would yield equally to the ungenial influence, and be converted into one frozen and lifeless mass. Among the almost numberless forms, therefore, which the orbits of the planets might assume, the production and maintenance of organized existences, such, at least, as those with which we are familiar, required that a selection should be made within narrow limits; and that selection has been made. Every one of the planets, with the exception only of three of the greatest of these bodies, viz. Mercury, Juno, and Pallas, which their peculiar circumstances may account for, move in an orbit nearly approaching to a circle. The earth's orbit, for example, only deviates from an exact circle, by the thirteenth part of its distance from the centre; and, though the deviation of all the other planets, except Venus, is somewhat more than this, that deviation is so small, unless in the instances already alluded to, that it need scarcely be mentioned as a source of inconvenience. "Taking the solar system altogether," says Whewell, "the regularity of its structure is very remarkable. The diagram, which represents the orbits of the planets, might have consisted of a number of ovals, narrow and wide in all degrees, intersecting and interfering with each other, in all directions. The diagram does consist, as all who have opened a book of astronomy know, of a set of figures, which appear, at first sight, concentric circles, and which are very nearly so; no where approaching to any crossing or interfering, except in the case of the small planets, already noticed as irregular. No one, looking at this common

diagram, can believe that the orbits were made to be so nearly circles, by chance, any more than he can believe that a target, such as archers are accustomed to shoot at, was painted in concentric circles by the accidental dashes of a brush in the hands of a blind man.'

"

Another peculiarity in the motions of the planets, is, that they are all in the same direction, and nearly in the same plane. It is quite evident, that, had chance originated these motions, they might, and probably would, have moved round the sun, both as to direction, and as to the plane of their orbit, in very different ways. Now, to those who are acquainted with the properties of the law of attraction, it will appear evident, that a most important object is served by the arrangement which actually subsists. Let it be observed, that such is the extraordinary nature of this law, that every particle of matter attracts, and is attracted by every other particle, the power, of course, being greater, in proportion to the quantity of each mass, and its nearness. The consequence of this is, that not only does the great central mass attract the smaller bodies, so as to cause them to revolve round it, but each of these smaller bodies also attracts the others; and this mutual attraction, which, it is easy to perceive, must be of a very complicated nature, and may produce the most extensive effects, requires to be nicely adjusted, in order to preserve the stability of the system. If the numerous globes, of which our system is composed, were to move in their respective orbits, without any such adjustment, our system would be far indeed from being stable. The disturbing forces, which might only be trifling, when a year, or even an age, was considered, might, in a long series of ages, accumulate to such an amount, as totally to disorganize and subvert the whole frame.

Nor is this a mere gratuitous hypothesis. Astronomers have actually discovered, in our solar system, an apparent tendency to derangement. Changes have been taking * Whewell's Bridgewater Treatise, p. 156.

place, owing to the cause just mentioned, which, at first sight, appear to be of an alarming nature. The eccentricity of the earth's orbit, has been gradually diminishing; the moon has been approaching nearer the earth, and accelerating her motion; and the obliquity of the ecliptic has been diminishing. These changes have been going on, from the period of the first scientific observations, to the present day, and are still in progress. Are they to continue without end? If so, the present system of things is tending to destruction.

This question has, by an amazing effort of calculation, been satisfactorily answered. Aided by the mathematical investigations of ages, two celebrated French philosophers, Lagrange and Laplace, have solved the problem, and have demonstrated, that "the planetary system will only oscillate about a mean state, and will never deviate from it, except by a very small quantity."* This remarkable result depends on these three conditions,—that the orbits of the planets are nearly circular; that these orbits are nearly in the same plane; and that they all move in the same direction.

Had any one of these conditions been different, the equilibrium of the system would not have been maintained; the tendencies to derangement would not have been counteracted, but, on the contrary, year after year, would have been accelerated by accumulation; and, sooner or later, the whole fabric would have broken up, and been dissolved by its own inherent defect.

It is unnecessary to enter into any argument, to show that the combination of the various arrangements alluded to, could not have occurred without design;—that the adjustment is that of an Intelligent Cause; and that it affords an unequivocal proof of consummate and adorable wisdom.

*Laplace, Expos. du Syst. du Monde, p. 441.

THIRD WEEK-FRIDAY.

VI. THE STARRY HEAVENS.-RESISTING MEDIUM.

We have seen, in the case of the planets, including also their satellites, that Supreme Wisdom has so balanced our system, that the disturbing forces, to which it is subjected by the mutual attraction of the heavenly bodies, will, in consequence of simple but selected arrangements, in the course of ages, correct themselves, so as never to endanger any violent change from such mechanical causes, so far, at least, as the power of attraction is concerned. This is highly satisfactory, as a demonstration against the atheistical doctrine, which would exclude from the universe the operation of a Designing Cause. It does not, however, prove the absolute permanency of the system, and we know, from the " more sure word of prophecy," that it is not destined to last for ever.

There is, indeed, another element to be taken into consideration, which the French philosophers, already alluded to, have overlooked or rejected, but which bears directly upon the question of inherent stability,-I mean the question regarding a resisting medium. All their calculations have been founded on the two simple powers of attraction and inertia, under the supposition that these powers acted in empty space, without the existence of any impeding force. If it be found, therefore, that a resisting medium actually exists in the system; that is, that there is some fluid matter, however rare, in which the celestial bodies move, then this one fact will overturn the conclusion as to the absolute and inherent permanency of the present scheme of things, so far as mechanical powers are concerned. Nor will this discovery invalidate the reasoning in the preceding paper; for it will still remain a truth, worthy of the deepest admiration, that the plan was adopted, which, of all others, is best