333viness does not naturally allow a greater swiftness: but even if it were conceded that its speed is always intensified without end, it would still not reach a swiftness without end.
From the things that have thus far been written, it will be easy for anyone to find the cause for which heavy things in their natural motions do not observe those ratios which we had assigned to them when we discussed the matter {1}; namely, the ratios of their heavinesses, which they have in the medium through which they are moved.For since at the beginning of their motion they are not moved in accordance with their heaviness, because they are impeded by a contrary force, it will surely not be astonishing if the swiftnesses do not observe the ratios of the heavinesses; on the contrary, and this surely seems remarkable, lighter things go down more swiftly than heavier ones at the beginning. Others, too, {1} have tried to assign a cause for this remarkable effect; since they have not been successful, we will in the next chapter refute them and endeavor to bring forth the true cause.
This question, surely, is no less elegant than difficult: others also, like Averroes and those who follow him, have tried to explain its solution; and, in my opinion, they have worked in vain, by laying down certain unattractive hypotheses. For, they say {1} that air in its proper region is heavy; from this it follows that, those things that will have more air, in the place of air are more heavy (and this is also Aristotle's opinion): the result of this is that , for example, since a sphere of wood has within itself more air than one of lead, it has 3 weight exerting elements[gravantia:see my note below], namely air, water and earth; but lead, since within itself it is weak in air, has, as it were, only 2 weight exerting elements[?gravia cf. ms;see my notes below], the wood sphere will go down more swiftly than the lead one. {2}Not content with this, they also say that rare lead is heavier in air than dense iron because there are more parts of air in rare lead than in the dense iron. There is no one who could fail to see