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ty of reflections. We shall state only one or two of those that most obviously occur.
When we consider the provision made by nature for the stability and permanence of the planetary system, a question arises, which was before hinted at, whether is this stability necessary or contingent, the effect of an unavoidable or an arbitrary arrangement ?—If it is the necessary consequence of conditions which are themselves necessary, we cannot infer from them the existence of design, but must content ourselves with admiring them as simple and beautiful truths, having a necessary and independent existence. If, on the other hand, the conditions from which this stability arises necessarily, are not necessary themselves, but the consequences of an arrangement that might have been different, we are then entitled to conclude, that it is the effect of wise design exercised in the construction of the universe.
Now, the investigations of Laplace enable us to give a very satisfactory reply to these questions; viz. that the conditions essential to the stability of a system of bodies gravitating mutually to one another, are by no means necessary, insomuch that systems can easily be supposed in which no such stability exists. The conditions essential to it, are the movement of the bodies all in one directiontheir having orbits of small eccentricity, or not far different from circles-and having periods of revo
lution not commensurable with one another. Now, these conditions are not necessary; they may easily be supposed different; any of them might be changed, while the others remained the same. The appointment of such conditions therefore as would necessarily give a stable and permanent character to the system, is not the work of necessity; and no one will be so absurd as to argue, that it is the work of chance: It is therefore the work of design, or of intention, conducted by wisdom and foresight of the most perfect kind. Thus the discoveries of Lagrange and Laplace lead to a very beautiful extension of the doctrine of final causes, the more interesting the greater the objects are to which they relate. This is not taken notice of by Laplace; and that it is not, is the only blemish we have to remark in his admirable work. He may have thought that it was going out of his proper province, for a geometer or a mechanician to occupy himself in such speculations. Perhaps, in strictness, it is so; but the digression is natural: and when, in any system, we find certain conditions established that are not necessary in themselves, we may be indulged so far as to inquire, whether any explanation of them can be given, and whether, if not referable to a mechanical cause, they may not be ascribed to intelligence.
When we mention, that the small eccentricity of the planetary orbits, and the motion of the planets
in the same direction, are essential to the stability of the system, it may naturally occur, that the comets, which obey neither of these laws in their motion, may be supposed to affect that stability, and to occasion irregularities which will not compensate one another. This would, no doubt, be the effect of the comets that pass through our system, were they bodies of great mass, or of great quantity of matter. There are many reasons, however, for supposing them to have very little density; so that their effect in producing any disturbance of the planets is wholly inconsiderable.
An observation somewhat of the same kind is applicable to the planets lately discovered. They are very small; and therefore the effect they can have in disturbing the motions of the larger planets is so inconsiderable, that, had they been known to Laplace, (Ceres only was known,) they could have given rise to no change in his conclusions. The circumstance of two of these planets having nearly, if not accurately, the same periodic time, and the same mean distance, may give rise to some curious applications of his theorems. Both these planets may be considerably disturbed by Jupiter, and perhaps by Mars.
Another reflection, of a very different kind from the preceding, must present itself, when we consider the historical details concerning the progress of physical astronomy that have occurred in the fore
going pages. In the list of the mathematicians and philosophers, to whom that science, for the last sixty or seventy years, has been indebted for its improvements, hardly a name from Great Britain falls to be mentioned. What is the reason of this? and how comes it, when such objects were in view, and when so much reputation was to be gained, that the country of Bacon and Newton looked silently on, without taking any share in so noble a contest? In the short view given above, we have hardly mentioned any but the five principal performers; but we might have quoted several others, Fontaine, Lambert, Frisi, Condorcet, Bailly, &c. who contributed their share to bring about the conclusion of the piece. In the list, even so extended, there is no British name. It is true, indeed, that before the period to which we now refer, Maclaurin had pointed out an improvement in the method of treating central forces, that has been of great use in all the investigations that have a reference to that subject. This was the resolution of the forces into others parallel to two or to three axes given in position and at right angles to one another. In the controversy that arose about the motion of the apsides in consequence of Clairaut's deducing from theory only half the quantity that observation had established, as already stated, Simpson and Walmsley took a part; and their essays are allowed to have great merit. The late Dr Matthew
Stewart also treated the same subject with singular skill and success, in his Essay on the Sun's Distance. The same excellent geometer, in his Physical Tracts, has laid down several propositions that had for their object the determination of the Moon's irregularities. His demonstrations, however, are all geometrical; and leave us to regret, that a mathematician of so much originality preferred the elegant methods of the ancient geometry to the more powerful analysis of modern algebra. Beside these, we recollect no other names of our countrymen distinguished in the researches of physical astronomy during this period; and of these none made any attempt toward the solution of the great problems that then occupied the philosophers and mathematicians of the Continent. This is the more remarkable, that the interests of navigation were deeply involved in the question of the lunar theory; so that no motive, which a regard to reputation or to interest could create, was wanting to engage the mathematicians of England in the inquiry. Nothing, therefore, certainly prevented them from engaging in it, but consciousness that, in the knowledge of the higher geometry, they were not on a footing with their brethren on the Continent. This is the conclusion which unavoidably forces itself upon us, and which will be but too well confirmed by looking back to the particulars which we stated in the beginning of this review, as either es