He says sometimes, that the air is light and mounts
upwards, and sometimes, that it is neither heavy nor light.
For in his Second Book of Motion he says, that the fire,
being without gravity, ascends upwards, and the air like to
that; the water approaching more to the earth, and the air
to the fire. But in his Physical Arts he inclines to the
other opinion, that the air of itself has neither gravity nor
levity.
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