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those which move should be cold: for, iri fa&, comets are bodies on fire, yet revolve round a centre: nor does this order obtain between the primary planets and their secondaries, which are all opaque. When we consider, therefore, that the sun is one; that the planets going round it are, at least, seven; that it is indifferent to their nature which are luminous and which are opaque; and also, in what order with respect to each other, these two kinds of bodies are disposed; we may judge of the improbability of the present arrangement tak* ing place by chance.
If, by way of accounting for the state in which we find the solar system, it be alledged (and this is one amongst the guesses of those who reject an intelligent Creator) that the planets themselves are only cooled or cooling masses, and were once, like the fun, many thousand times hotter than red hot iron j then it follows, that the fun also himself must be in his progress towards growing cold; which puts an end to the possibility of his having ex* isted, as he is, from eternity. This consequence arises out of the hypothesis with still more certainty, if we make a part of it, what the philosophers who maintain it, have usually
taught, that the planets were originally masses of matter struck off, in a state of fusion, from the body of the fun, by the percussion of a comet, or by a shock from some other cause with which we are not acquainted: for, if these masses, partaking of the nature and substance of the fun's body, have in process of time lost their heat, that body itself, in time likewise, no matter in how much longer time, must lose its heat also; and therefore be incapable of an eternal duration in the state in which we see it, either for the time to come, or the time past.
The preference of the present to any other mode of distributing luminous and opaque bodies I take to be evident. It requires more astronomy than I am able to lay before the reader, to shew, in its particulars, what would be the effect to the system, of a dark body at the centre, and of one of the planets being luminous: but I think it manifest, without either plates or calculation, first, that, supposing the neceflary proportion, of magnitude between the central and the revolving bodies to be preserved, the ignited planet would not be sufficient to illuminate and warm the rest of the system; secondly, that its light and heat
would would be imputed to the other planets, much more irregularly than light and heat are now received from the fun.
C) II. Another thing, in which a choice appears to be exercised; and in which, amongst the possibilities out of which the; choice was to be made, the number of those which were wrong, bore an infinite proportion to the number of those which were right, is in what geometricians call the axis of rotation. This matter I will endeavour to explain. The earth, it is well known, is not an exact globe, but an oblate spheroid, something like an orange. Now the axes of rotation, or the diameters upon which such a body may be made to turn round, are as many as can be drawn through its centre to opposite points upon its whole surface: but of these axes none are permanent, except either its shortest, diameter, i. e. that which passes through the heart of the orange from the place where the stalk is inserted into it, and which is but one; or its longest diameters, at right angles with the former, which must all terminate in the single circumfcience which goes round the thickest part of the orange. This shortest diameter is that upon which in fact the earth turns; and it is, as the
reader reader sees, what it ought to be, a permanent axis: whereas, had blind chance, had a casual impulse, had a stroke or push at random, set the earth a-spinning, the odds were infinite, but that they had sent it round upon a wrong axis. And what would have been the consequence? The difference between a permanent axis and another axis is this. When a spheroid in a state of rotatory motion gets upon a permanent axis, it keeps there; it remains steady and faithful to its position; its poles preserve their direction with respect to the plane and to the centre of its orbit: but, whilst it turns upon an axis which is not permanent, (and the number of those, we have seen, infinitely exceeds the number of the other), it is always liable to shift and vacillate from one axis to another, with a corresponding change in the inclination of its poles. Therefore, if a planet once set off revolving upon any other than its shortest, or one of its longest axes, the poles on its surface would keep perpetually changing, and it never would attain a permanent axis of rotation. The effect of this unfixedness and instability would be, that the equatorial parts of the earth might become the polar, or the polar the equatorial; to the utter 2 E destruction
destruction of plants and animals, which are not capable of interchanging their situations, but are respectively adapted to their own. As to ourselves, instead of rejoicing in our temperate zone, and annually preparing for the moderate vicissitude, or rather the agreeable succession of seasons, which we experience and expect, we might come to be locked up in the ice and darkness of the arctic circle, with bodies neither inured to its rigors, nor provided with shelter or desence against them. Nor would it be much better, if the trepidation of our pole, taking an opposite course, should place us under the heats of a vertical fun. But, if it would fare so ill with the human inhabitant, who can live under greater varieties of latitude than any other animal, still more noxious would this translation of climate have proved to life in the rest of the creation; and, most perhaps of all, in plants. The habitable earth, and its beautiful variety, might have been destroyed, by a simple mischance in the axis of rotation.
C) III. All this however proceeds upon a supposition of the earth having been formed at first an oblate spheroid. There is another supposition; and, perhaps, our limited infor