Page:Discourse Concerning the Natation of Bodies.djvu/21

Rh Solid that weighs above 100 pounds: in that we have demonstrated, That it sufficeth, that such difference be found between the Specificall Gravities of the Mediums and Moveables, let the particular and absolute Gravities be what they will: insomuch, that a Solid, provided that it be Specifically less grave than the water, although its absolute weight were 1000 pounds, yet may it be born up and elevated by ten pounds of water, and less: and on the contrary, another Solid, so that it be Specifically more grave than the water, though in absolute Gravity it were not above a pound, yet all the water in the Sea, cannot raise it from the Bottom, or float it. This sufficeth me, for my present occasion, to have, by the above declared Examples, discovered and demonstrated, without extending such matters farther, and, as I might have done, into a long Treatise: yea, but that there was a necessity of resolving the above proposed doubt, I should have contented my self with that only, which is demonstrated by Archimedes, in his first Book De Insidentibus humido: where in generall termes he infers and confirms the same Conclusions, namely, that Solids (a) less grave than water, swim or float upon it, the (b) more grave go to the Bottom, and the (c) equally grave rest indifferently in all places, yea, though they should be wholly under water.

But, because that this Doctrine of Archimedes, perused, transcribed and examined by Signor Francesco Buonamico, in his fifth Book of Motion, Chap. 29, and afterwards by him confuted, might by the Authority of so renowned, and famous a Philosopher, be rendered dubious, and suspected of falsity; I have judged it necessary to defend it, if I am able so to do, and to clear Archimedes, from those censures, with which he appeareth to be charged. Buonamico rejecteth the Doctrine of Archimedes, first, as not consentaneous with the Opinion of Aristotle, adding, that it was a strange thing to him, that the Water should exceed the Earth in Gravity, seeing on the contrary, that the Gravity of water, increaseth, by means of the participation of Earth. And he subjoyns presently after, that he was not satisfied with the Reasons of Archimedes, as not being able with that Doctrine, to assign the cause whence it comes, that a Boat and a Vessell, which otherwise, floats above the water, doth sink to the Bottom, if once it be filled with water; that by reason of the equality of Gravity, between the water within it, and the other water without, it should stay a top; but yet, nevertheless, we see it to go to the Bottom.

He farther addes, that Aristotle had clearly confuted the Ancients, who said, that light Bodies moved upwards, 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, Rh