, in such a way that its size becomes equal to the size of a, air b will then somehow be another species of air heavier than air a is; what then is so astonishing if air b goes down in the air of which a is a portion? </s>
<s id="id.1.1.11.04.02">Thus the reason why the inflated bladder pulls by force more is evident: for the air which is in it is heavier than the surrounding air, to the extent that it contains more of the same matter in a smaller place. </s>
<s id="id.1.1.11.04.03">It is thus manifest that the argument concerning the bladder has no soundness; since, wanting to show that air that is free and rare, as is its nature, is heavy, he then takes in his example air condensed by force and compressed in a narrow place.</s>
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<s id="id.1.1.11.05.00"/>
<s id="id.1.1.11.05.01">As for the argument of those who then say that air is heavy since it carries more easily heavy things downward than light ones upward, I answer that this form of arguing goes diametrically against those who argue it. </s>
<s id="id.1.1.11.05.02">For if that medium is to be thought heavy because it carries more easily heavy things downward, air will then be heavier than water: for things that are carried downward, go down more easily and more swiftly in air than in water. </s>
<s id="id.1.1.11.05.03">Add this: it has been demonstrated above {1} that heavy things which are carried downward in water, go down with as much force, as that by which their heaviness exceeds the heaviness of a size of water equal to their size. </s>
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<s id="id.1.1.11.06.00.fig"/>
<s id="id.1.1.11.06.01">If consequently there were a certain heavy body, as, for instance, a body a, whose heaviness is 8, and the heaviness of water b, whose size is equal to the size of a, is 4, then solid a in water will be swiftly and easily carried downward as 4; but if subsequently the same body is carried through a medium lighter than medium b, so that a size of such a medium as great as the size of this same b would have a heaviness of only 3, then a in such a medium would be moved swiftly and easily as 5.</s>
<s id="id.1.1.11.06.02"> Therefore it is evident that this same body a is moved more easily downward through lighter media than through heavier ones: hence it follows necessarily that a medium is to be thought lighter, the more easily heavy things are moved downward in it; of which they were asserting the contrary.</s>
<s id="id.1.1.11.06.03">To whom, then, is it not now perfectly clear that, if air were still lighter, heavy things would be moved downward more easily? </s>
<s id="id.1.1.11.06.04">And if this is so, it follows that air is light for this reason, because heavy things are easily carried downward in it. </s>
<s id="id.1.1.11.06.05">By reasoning in the opposite manner about light things, we will conclude that that medium is to be thought heavy, through which light things are more easily carried upward; but that medium is to be thought light, through which light things rise with difficulty. </s>
<s id="id.1.1.11.06.06">Therefore, both because in air light things are moved upward with more difficulty, and because in it heavy things are moved downward more easily, it follows that air </s>
