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To Expel the Air from Cans

Air, by heating, expands many times its own bulk; consequently, if you take a jar and cover it tightly with the exception of a hole the size of a pin through the cover, and set it in boiling water, as air expands 20 times its bulk by heating, it is obvious that & of the air pases out through the pin hole in the cover; now drop a little sealing wax or solder over the pin hole and you have but of the air course the fruit and syrup, if put into the jar cold, displaces most of the air; but putting it in as hot as it can be, and filling as full as possible, expels the air to all intents and purposes. Cans managed in this way, when made of sheet metal, frequently collapse from outside atmospheric pressure as they cool off, showing that the exhaustion was complete; even more so than needed.