so assured as you ought to do of the earth's motion: are you the less happy on that account? Oh! as to that opinion, I am sure I do my duty; you have no right to complain of me, for I firmly believe that the earth turns. Yet I have not given you the most convincing proof of it, answered I. You use me very ill, said she, to make one believe things without sufficient reason; am I unworthy to hear the best arguments? I wished to prove my opinions, I replied, by easy, entertaining arguments; would you have had me make use of such solid, sturdy ones as I should have attacked a doctor with? Certainly, said she; now fancy me a doctor, and let me have this new proof of the earth's motion. With all my heart, answered I; it is this, and I am vastly pleased with it, because I think I found it out myself; but it is so good and so natural that I can hardly hope to have been the inventor. I am sure an obstinate learned man who wished to oppose it, would be forced to talk a great deal on the occasion; and that is the only way in which a scholar can be overcome. It is evident either that all the heavenly bodies go round the earth in four-and-twenty hours, or the earth, turning on her axis, only imagines the motion in them. It is the most improbable thing in the world that they should in reality go round the earth in that short space of time, though we are not at first aware of the absurdity of such an opinion. All the planets certainly revolve round the sun: but these revolutions are unequal from the unequal distances at which they are placed from the sun: the most remote, as we might naturally suppose, take a longer time than the rest. This order is observed even in the satellites that go round a large planet. Jupiter's four moons, and the five belonging to Saturn, require a longer or shorter time to move round their planet according to their distance from it. It is further ascertained that the planets have a rotation on their own axis; the time of this is likewise unequal; we cannot tell the cause of such inequality, whether it depends on the different size, or the degree of solidity of the planets, or on the different degrees of rapidity of the vortices in which they are enclosed, and the liquid matter by which they are carried along;[57] this inequality however is certain, and in general we find that the order of nature is such as to admit of particular variations in things that are regulated by the same rules. [Footnote 57: We can assign no reason; the irregularity depends on the original cause, whatever that cause may be, which at first determined their motions.]