air expands greatly when heated, / but since air is practically invisible, /
we are not ordinarily conscious of any change in it. ❷the expansion of air /
can be readily shown / by putting a drop of ink in a thin glass tube, / inserting
the tube in the cork of a flask, / and applying heat to the flask. ❸ the ink is
forced up the tube / by the expanding air. ❹the fall(→ rise) of the drop of
ink shows / that the air in the flask occupies more space than formerly, /
and since the quantity of air has not changed, / each cubic inch of space
must hold less warm air than it held cold air; ❺ that is, one cubic inch of
warm air weighs less than one cubic inch of cold air.

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