The lighter Bodies ascend more swiftly through Water.
And, howbeit, Experience shewes, that the Bodies, successively less grave, do most expeditiously ascend in water, it cannot be doubted, but that the Ignean Exhalations do ascend more swiftly through the water, than doth the Air: which Air is seen by Experience to ascend more swiftly through the Water, than the Fiery Exhalations through the Air: Therefore, we must of necessity conclude, that the said Fiery Exhalations ascend thorow the Water more swiftly than doth the Air; & the Air ascends more swiftly thorow the Water, than Fire thorow the Air. Exhalations do much more expeditiously ascend through the Water, than through the Air; and that, consequently, they are moved by the Impulse of the Ambient Medium, and not by an intrinsick Principle that is in them, of avoiding the Centre of the Earth; to which other grave Bodies tend.
The Authors confutation of the Peripateticks Causes of Natation & Submersion.
To that which for a finall conclusion, Signor Buonamico produceth of going about to reduce the descending or not descending, to the easie and uneasie Division of the Medium, and to the predominancy of the Elements: I answer, as to the first part, that that cannot in any manner be admitted as a Cause, being that in none of the Fluid Mediums, as the Air, the Water, and other Liquids, there is any Resistance against Division, but all by every the least Force, are Water & other fluids void of Resistance against Division. divided and penetrated, as I will anon demonstrate: so, that of such Resistance of Division there can be no Act, since it self is not in being. As to the other part, I say, that the predominancy of the Elements in Moveables, is to be considered, as far as to the excesse The predominancy of Elements in Moveables to be considered only in relation to their excess or defect of Gravity in reference to the Medium. or defect of Gravity, in relation to the Medium: for in that Action, the Elements operate not, but only, so far as they are grave or light: therefore, to say that the Wood of the Firre sinks not, because Air predominateth in it, is no more than to say, because it is less grave than the Water. Yea, even the immediate Cause, is its being less grave than the Water: and it being under the predominancy of the Air, is the The immediate Cause of Natation is that the Moveable is less grave than the Water. Cause of its less Gravity: Therefore, he that alledgeth the predominancy of the Element for a Cause, brings the Cause of the Cause, and not the neerest and immediate Cause. Now, who knows not that the true Cause is the immediate, and not the mediate? Moreover, The Peripateticks alledge for the reason of Natation the Cause of the Cause. he that alledgeth Gravity, brings a Cause most perspicuous to Sence: Gravity a Cause most perspicuous to sence. The cause we may very easily assertain our selves; whether Ebony, for example, and Firre, be more or less grave than water: but whether Earth or Air predominates in them, who shall make that manifest? Certainly, no Experiment can better do it than to observe whether they swim or sink. So, that he who knows, not whether such a Solid swims, unless when he knows that Air predominates in it, knows not whether it swim, unless he sees it swim, for then he knows that it swims, when he knows that it is Air that predominates, but knows not that Air hath the predominance, unless he sees it swim: therefore, he knows not if it swims, till such time as he hath seen it swim.
Let us not then despise those Hints, though very dark, which Reason, after some contemplation, offereth to our Intelligence, and lets be content to be taught by Archimedes, that then any Body shall submerge in water, when it shall be specifically more grave than it, Lib 1. of Natation Prop. 7 and that if it shall be less grave, it shall of necessity swim, and Id. Lib. 1. Prop. 4. that it will rest indifferently in any place under water, if its Gravity be perfectly like to that of the water.
These things explained and proved, I come to consider that which Id. Lib 1. Prop. 3. offers it self, touching what the Diversity of figure given unto the said Moveable hath to do with these Motions and Rests; and proceed to affirme, that,
THEOREME V.
Diversity of Figure no Cause of its absolute Natation or Submersion.