Hypsometer

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A Hypsometer is an instrument for measuring altitude which employs the principles that the boiling point of a liquid is lowered by diminishing the barometric pressure, and that the barometric pressure varies with the height of the point of observation.

The instrument consists of a cylindrical vessel in which the liquid, usually water, is boiled, surmounted by a jacketed column, in the outer partitions of which the vapour circulates, while in the central one a thermometer is placed. To deduce the height of the station from the observed boiling point, it is necessary to know the relation existing between the boiling point and pressure, and also between the pressure and height of the atmosphere.

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• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.