And I (Ammonius bidding me oppose him) said: Sir, your suppositions which require a vacuum to be granted I shall admit; but you err in supposing that a vacuum is conducive either to the preservation or conveyance of sound. For that which cannot be touched, acted upon, or struck is peculiarly favorable to silence. But sound is a stroke of a sounding body; and a sounding body is that which is homogeneous and uniform, easy to be moved, light, smooth, and, by reason of its tenseness and continuity, obedient to the stroke; and such is the air. Water, earth, and fire, are of themselves soundless; but each of them makes a noise when air falls upon or gets into it. And brass hath in it no vacuum; but being mixed with a smooth and gentle air it answers to a stroke, and is sounding. If the eye may be judge, iron must be reckoned to have a great many vacuities, and to be porous like a honey-comb, yet it is the dullest, and sounds worse than any other metal. Therefore there is no need to trouble the night to contract and condense its air, that in other parts we may leave vacuities and wide spaces; as if the air would hinder and corrupt the substance of the sounds, whose very substance, form, and power itself is. Besides, if your reason held, misty and extreme cold nights would be more sonorous than those which are temperate and clear, because then the atoms in our atmosphere are constipated, and the spaces which they left remain empty; and, what is more obvious, a cold day should be more sonorous than a warm summer’s night; neither of which is true. Therefore, laying aside that explication, I produce Anaxagoras, who teacheth that the sun makes a tremulous motion in the air, as is evident from those little motes which are seen tossed up and down and flying in the sunbeams. These (says he), being in the day-time whisked about by the heat, and making a humming noise, lessen or drown other sounds; but at night their motion, and consequently their noise, ceaseth.