a deprivation of heaviness, when the mobile is impelled upward; but when impelled downward, it is a deprivation of lightness. </s>
<s id="id.1.2.4.04.04">But a person will not marvel at how a thrower can, by directing a heavy thing upward, deprive it of heaviness and render it light, if he does not marvel at how fire can deprive iron of cold, by introducing heat. </s>
<s id="id.1.2.4.04.05"> A mobile, then, is moved upward by the thrower, so long as it is in the latter's hand and is deprived of heaviness; similarly, the iron is moved, in an alterative motion, towards heat, so long as the iron is in the fire and it is deprived by it of cold: the motive force, namely lightness, is conserved in the stone, when what has moved it no longer touches it; the heat is conserved in the iron, when it is removed from the fire: the impressed force is progressively weakened in the projectile when it is apart from the projector; the heat is diminished in the iron, when fire is no longer present: the stone finally is reduced to rest; similarly, the iron comes back to natural cold: motion is impressed by the same force more in a mobile that is resisting than in one which resists less, as in a stone more than in light pumice: and heat, similarly, is impressed in a more penetrating way by the same quantity of fire in very hard and very cold iron than in tenuous and less cold wood. </s>
<s id="id.1.2.4.04.06">He would be ridiculous, who would say that the air previously heated by the fire, once the fire is out or removed to a distance, conserves the heat in the iron; since iron is brought to white-heat even in very cold air: and he is even more ridiculous, who would believe that mobility would be conserved in the projectile by air which is motionless or often enough blows in the opposite direction. </s>
<s id="id.1.2.4.04.07">And who will not say that iron is cooled more swiftly in cold air by the coldness of the air? and who of sound mind will not say that air, either by staying at rest or by blowing in the opposite direction, hinders motion? </s>
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<s id="id.1.2.4.05.00"/>
<s id="id.1.2.4.05.01">But let an even more beautiful example be given. </s>
<s id="id.1.2.4.05.02">You are astonished by what comes out of the hand of the thrower and is impressed in the projectile; and you are not astonished by what comes out of the hammer and is transferred into the bell of the clock, and how it comes about that so great a sound is transported from a silent hammer into a silent bell, and how it is conserved in the latter, in the absence of what has struck it. </s>
<s id="id.1.2.4.05.03"> The bell is struck by a striking thing; the stone is moved by a moving thing: the bell is deprived of silence; the stone is deprived of rest: a sonorous quality is introduced in the bell contrary to its natural silence; a motive quality is introduced in the stone contrary to its state of rest: the sound is conserved in the bell, in the absence of what has struck it; the motion is conserved in the stone, in the absence of what has moved it: the sonorous quality is progressively weakened in the bell; the motive quality is gradually weakened </s>
