The experiment was publicly made
in 1650 at the Imperial Diet at Rendsborg, in the presence of the
Emperor Ferdinand III. and a large number of princes and nobles, much
to their astonishment.
As compared with water, the air (the barometer indicating 30 deg., and the
thermometer 55 deg.) is 833 times lighter.
It is this weight of the atmosphere which counterbalances that of a
column of mercury 29 inches in height, and a column of water 32 to 34
feet in height.
The old quaint notion of Nature's abhorring a vacuum was found to be
practically only an assertion that the air had weight. The ordinary
pump, commonly called the suction-pump, is constructed on this
principle. The weight of the atmosphere at the level of the sea is
found to be the same all over the world.
* * * * *
We find the atmosphere with another characteristic,--Elasticity.
However it may be compressed, air returns, on liberation, to its
original volume, and while thus perfectly elastic it is also the most
compressible of bodies. This elasticity arises from the repulsive
force of its particles, and is always equal to the compressive force
which it balances.
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