_B._ Then he contradicteth himself. For if all heavy bodies tend naturally to one centre, they shall never settle in a plane, but in a spherical superficies. But against this, that such an horizontal plane is found in water by experience, I say it is impossible. For the experiment cannot be made in a basin, but in half a mile at sea experience visibly shows the contrary. According to this, he should think also that a pair of scales should hang parallel. _A._ He thinks that too. _B._ Let us then leave this experiment. What says he farther concerning gravity? _A._ He takes for granted, not as an experiment but an axiom, that nature worketh not by election, but _ad ultimum virium_, with all the power it can. _B._ I think he means, (for it is a very obscure passage), that every inanimate body by nature worketh all it can without election; which may be true. But it is certain that men, and beasts, work often by election, and often without election; as when he goes by election, and falls without it. In this sense I grant him, that nature does all it can. But what infers he from it? _A._ That naturally every body has every way, if the ways oppose not one another, an endeavour to motion; and consequently, that if a vessel have two holes, one at the side, another at the bottom, the water will run out at both. _B._ Does he think the body of water that runs out at the side, and that which runs out at the bottom, is but one and the same body of water? _A._ No, sure; he cannot think but that they are two several parts of the whole water in the vessel. _B._ What wonder is it then, if two parts of water run two ways at once, or a thousand parts a thousand ways? Does it follow thence that one body can go more than one way at once? Why is he still meddling with things of such difficulty? He will find at last that he has not a genius either for natural philosophy or for geometry. What other suppositions has he? _A._ My first author had affirmed, that a lighter body does not gravitate on a heavier; against this Dr. Wallis thus argueth: Let there be a siphon, A B C D, filled with quicksilver to the level A D; if then you pour oil upon A as high as to E, he asketh if the oil in A E, as being heavy, shall not press down the quicksilver a little at A, and make it rise a little at D, suppose to F; and answers himself, that certainly it will; so that it is neither an experiment nor an hypothesis, but only his opinion. _B._ Whatsoever it be, it is not true; though the doctor may be pardoned, because the contrary was never proved. _A._ Can you prove the contrary?