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than sound. Light travels further than sound. Whether light is conveyed in the body of the air, like sound, is uncertain. Light moves only in a straight line, sound obliquely and in any way; for when anything is seen under the shadow of a screen, it is not to be supposed that the light itself penetrates that screen, but only that it illuminates the air around it; which likewise somewhat brightens the neighbouring air behind the screen; whereas a sound made on one side of a wall is heard without much diminution on the other. Sound likewise is heard from within a solid body, though more faint; as we see in sounds within the bloodstone, or in bodies struck under water; whereas light in a solid and untransparent body that is stopped on all sides, is not seen at all. Lastly, all sound is generated in motion and a manifest elision of bodies; but light not so.

For the oppositions to light, unless you take privations to mean oppositions, there are none that occur to me; but what is most credible is that sluggishness of bodies in their parts is the chief enemy to light. For there is scarce anything luminous which is not either in its own nature very movable, or excited by heat or motion or the vital spirit. Other instances.

I mean always, not only that other instances are to be sought for (for these few are only adduced by way of example), but likewise that new topics of inquiry should be added, as the nature of things leads the way.

TRANSLATIONS

OF

THE PHILOSOPHICAL WORKS.

PART II.

THOUGHTS

ON TIE

NATURE OF THINGS.

VOL. V.

EE

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