He farther addes[18], that _Aristotle_ had clearly confuted the Ancients, who said, that light Bodies moved upwards[19], driven by the impulse of the more grave Ambient: which if it were so, it should seem of necessity to follow, that all naturall Bodies are by nature heavy, and none light: For that the same would befall the Fire and Air, if put in the Bottom of the water. And, howbeit, _Aristotle_ grants a Pulsion in the Elements, by which the Earth is reduced into a Sphericall Figure, yet nevertheless, in his judgement; it is not such that it can remove grave Bodies from their naturall places, but rather, that it send them toward the Centre, to which (as he somewhat obscurely continues to say,) the water principally moves, if it in the interim meet not with something that resists it, and, by its Gravity, thrusts it out of its place: in which case, if it cannot directly, yet at least as well as it can, it tends to the Centre: but it happens, that light Bodies by such Impulsion, do all ascend upward: but this properly they have by nature, as also, that other of swimming. He concludes, lastly[20], that he concurs with _Archimedes_ in his Conclusions; but not in the Causes, which he would referre to the facile and difficult Separation of the _Medium_, and to the predominance of the Elements, so that when the Moveable superates the power of the _Medium_; as for example, Lead doth the Continuity of water, it shall move thorow it, else not. [18] His fourth Objection. [19] The _A_ncients denyed _A_bsolute Levity. [20] The causes of Natation & Submersion, according to the Peripateticks.