And besides (which is an evident sign) a barrel when full is not spoiled so soon as when it is half empty; because a great deal of air getting into the empty space troubles and disturbs the liquor, whereas the wine that is in the unemptied cask is preserved and defended by itself, not admitting much of the external air, which is apt to injure and corrupt it.
But the oil gave us the most difficulty.

One thought that the bottom of the oil was affected, because it was foul and troubled with the lees; and that the top was not really better than the rest, but only seemed so, because it was farthest removed from those corrupting particles.
Others thought the thickness of the liquor to be the reason, which thickness keeps it from mixing with other humids, unless blended together and shaken violently; and therefore it will not mix with air, but keeps it off by its smoothness and close contexture, so that it hath no power to corrupt it.

But Aristotle seems to be against this opinion, who hath observed that oil grows sweeter by being kept in vessels not exactly filled, and afterwards ascribes this melioration to the air; for more air, and therefore more powerful to produce the effect, flows into a vessel not well filled.
Well then! said I, the same quality in the air may spoil wine, and better oil.

For long keeping improves wine, but spoils oil.

Now the air keeps oil from growing old; for that which is cooled continues fresh and new, but that which is kept close up, having no way to exhale its corrupting parts, presently decays, and grows old.