That a contrary force is impressed more strongly in heavier things is evident from the things which, after being suspended by a thread, are put into a motion of going back and forth: for the heavier they are, the longer they will be moved. </s>
</p>
<p>
<s id="id.5.0.18.02.00"/>
<s id="id.5.0.18.02.01">Things that are more solid, more heavy and more dense conserve all contrary qualities longer, more sharply and more easily; such as stones, which in winter become far colder than air, but in summer warmer. </s>
</p>
</subchap2>
<subchap2>
<p>
<s id="id.5.0.19.00.00"/>
<s id="id.5.0.19.00.01">Aristotle says {1}: Things that are moved naturally are not moved through extrusion; because in this way the motion would be violent and it would be weakened at the end, although we see that it is increased. </s>
<s id="id.5.0.19.00.02">To that it is answered that violent motion is weakened when the mobile is out of the hand of the mover; but while it is linked to the mover -- as if we should say, of what is carried toward its proper place {1}, that it is moved by air through extrusion -- it is not necessary that at the end the motion becomes weaker. </s>
</p>
</subchap2>
<subchap2>
<p>
<s id="id.5.0.20.00.00"/>
<s id="id.5.0.20.00.01">The definition of the heavy and the light through motion handed down by tradition is not a good one {1}: for when a heavy or light thing is being moved, it is neither heavy nor light. </s>
<s id="id.5.0.20.00.02">For that thing is heavy which exerts weight on something; but what exerts weight on something else is resisted by that thing; hence a heavy thing, when it exerts weight, is not moved: as is evident if you have a stone in hand, which then will exert weight when the hand resists its heaviness; but if it is moved downward with the stone, the stone will not then exert weight on the hand. </s>
<s id="id.5.0.20.00.03">Hence the definition will better be: That thing is heavier which remains under things that are lighter. {1}</s>
<s id="id.5.0.20.00.04">For if we should say, Heavy is what remains downward, and light what remains upward, we would not be defining well, since upward and downward are not distinguished in fact, but only in logic. {1}</s>
</p>
</subchap2>
<subchap2>
<p>
<s id="id.5.0.21.00.00"/>
<s id="id.5.0.21.00.01">It must be considered whether, if there were a void above water, things that are moved in water would be moved more slowly or more swiftly; and whether different mobiles would observe the same ratio in their motions. </s>
</p>
</subchap2>
<subchap2>
<p>
<s id="id.5.0.22.00.00"/>
<s id="id.5.0.22.00.01">Downward motion is more natural by far than upward motion. {1}</s>
<s id="id.5.0.22.00.02">For upward motion entirely depends on the heaviness of the medium, which assigns an accidental </s>
