those which move fhould be cold: for, in fact, comets are bodies on fire, yet revolve round a centre: nor does this order obtain between the primary planets and their fecondaries, which are all opaque. When we confider, therefore, that the fun 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 or der with respect to each other, these two kinds of bodies are disposed; we may judge of the improbability of the present arrangement taking place by chance. If, by way of accounting for the state in which we find the folar fyftem, 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 maffes, and were once, like the fun, many thousand times hotter than red hot iron; then it follows, that the fun also himself must be in his progress towards growing cold; which puts an end to the poffibility of his having exifted, as he is, from eternity. This confequence arifes out of the hypothesis with ftill more certainty, if we make a part of it, what the philofophers who maintain it, have ufually taught, taught, that the planets were originally maffes of matter ftruck off, in a state of fusion, from the body of the fun, by the percuffion of a comet, or by a shock from fome other cause with which we are not acquainted; for, if these masses, partaking of the nature and subftance of the fun's body, have in process of time loft their heat, that body itself, in time likewise, no matter in how much longer time, must lose its heat alfo; and therefore be incapable of an eternal duration in the state in which we fee it, either for the time to come, or the time paft. The preference of the prefent to any other mode of diftributing luminous and opaque bodies I take to be evident. It requires more aftronomy than I am able to lay before the reader, to fhew, in its particulars, what would be the effect to the fyftem, of a dark body at the centre, and of one of the planets being luminous: but I think it manifeft, without either plates or calculation, firft, that, fuppofing the neceffary proportion of magnitude between the central and the revolving bodies to be preferved, the ignited planet would not be fufficient to illuminate and warm the rest of the fyftem; fecondly, that its light and heat would would be imparted to the other planets, much more irregularly than light and heat are now received from the fun. (*) 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, fomething like an orange. Now the axes of rotation, or the diameters upon which fuch a body may be made to turn round, are as many as can be drawn through its centre to oppofite points upon its whole furface: but of these axes none are permanent, except either its fhorteft diameter, i. e. that which paffes through the heart of the orange from the place where the ftalk is inferted into it, and which is but one; or its longeft diameters, at right angles with the former, which must all terminate in the single circumference which goes round the thickeft part of the This shortest diameter is that upon which in fact the earth turns; and it is, as the reader orange. reader fees, what it ought to be, a permanent axis: whereas, had blind chance, had a casual impulfe, had a ftroke or push at random, fet the earth a-spinning, the odds were infinite, but that they had fent it round upon a wrong axis. And what would have been the confequence? 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 pofition; its poles preferve their direction with refpect to the plane and to the centre of its orbit: but, whilft it turns upon an axis which is not permanent, (and the number of thofe, we have feen, infinitely exceeds the number of the other), it is always liable to fhift and vacillate from one axis tó another, with a correfponding change in the inclination of its poles. Therefore, if a planet once fet off revolving upon any other than its fhorteft, or one of its longeft axes, the poles on its furface would keep perpetually changing, and it never would attain a permanent axis of rotation. The effect of this unfixednefs and inftability would be, that the equatorial parts of the earth might become the polar, or the polar the equatorial; to the utter deftruction 2 E deftruction of plants and animals, which are not capable of interchanging their fituations, but are respectively adapted to their own. As to ourselves, instead of rejoicing in our temperate zone, and annually preparing for the moderate viciffitude, or rather the agreeable fucceffion 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 defence against them. Nor would it be much better, if the trepidation of our pole, taking an opposite course, fhould 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, ftill more noxious would this tranflation of climate have proved to life in the reft of the creation; and, moft perhaps of all, in plants. The babitable earth, and its beautiful variety, might have been destroyed, by a fimple mischance in the axis of rotation. (*) III. All this however proceeds upon a fuppofition of the earth having been formed at first an oblate fpheroid. There is another fuppofition; and, perhaps, our limited infor |