<s id="id.1.2.8.02.11">There is also a manifest example which happens quite often to divers and swimmers. </s>
<s id="id.1.2.8.02.12">For their natural heaviness is great enough for them to go down, if they want to, to the bottom of the sea, and then it is only by the action of their proper heaviness that they sink: but if they are impelled downward by an external mover, with no matter how great a force, e.g. if they are thrown from a very high place, like the top of a ship's mast, at the beginning their motion in water will surely be very excited and much beyond the natural; and yet this motion will be retarded by their proper absolute heaviness, which then, in comparison to the heaviness joined with the impetus received, amounts to lightness, and it will be retarded until in going down it has reached its natural slowness; and moreover if the water is deep enough, [the diver] will not suffer any greater injury at the bottom than if he had gone down by his proper natural motion from the surface of the water. </s>
<s id="id.1.2.8.02.13">And from this the following argumentation can be drawn: for if [a mobile] in going down were always accelerated in its motion, it would be capable of every swiftness whatever, so that no swiftness would be beyond the natural for it; and therefore it would not lose or reject the downward impetus received from the external mover, since at the end it would even have arrived naturally at this impetus: but experience teaches that the contrary occurs: hence it is evident to everyone that a definite and established swiftness is prescribed to natural motion in going down. {1}</s>
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<s id="id.1.2.8.03.00"/>
<s id="id.1.2.8.03.01">But even if the swiftness were always intensified and the length of the motion were without end, it would not however follow that the motion would finally attain a swiftness without end and the mobile a heaviness without end -- which will not be difficult to understand for those who are versed in mathematics. </s>
<s id="id.1.2.8.03.02">For this is like what seems impossible to nearly all who are incapable of following the demonstration: namely that two lines can be found which, being prolonged without end, always come closer, yet never meet; so that the distance between them always diminishes without end, yet never is consumed. </s>
<s id="id.1.2.8.03.03">But that such lines are given is known to all who have come upon either the asymptotes of the hyperbola in the Conics of Apollonius of Perga, or with the first conchoid curve of Nicomedes in the commentary of Eutocius of Asca</s>
