In his own words in his Personal Narrative of Travels…. Humboldt carried "An appatatus by Paul, proper to determine with the greatest precision the degree at which water boils at different heights, above the level of the ocean. The thermometer with a double nonius [vernier] had been constructed from the apparatus, which Mr. de Saussure employed in his excursions." (Alexander von Humboldt. Personal narrative of travels to the equinoctial regions of the New continent, during the years 1799-1804, by A. von Humboldt and A. Bonpland. translated from the French by Helen Maria Williams, 1814, p 39.) Note that Humboldt’s hypsometer (apparatus by Paul) data appear in the “degrés” column (column #17 from the left) of the Chimborazo diagram.
Modern steam-bath hypsometers differ only in detail from the types used in the 19th century, for the best work all use a multiple walled steam jacket to assure proper steam temperature equilibria and no radiative affects. For high precision thermometer readings late 19th and 20 century practice was to use a cathetometer (precision rule with telescope) with vernier rather than a vernier on the thermometer.
Hypsometers were used to calibrate the steam point of thermometers at known barometric pressures, or to find barometric pressure, and thus altitude, by measuring water’s boiling point.
Solderless copper steam generator with copper and brass double-walled screw-on steam jacket with enameled steel tripod stand. Displayed with a glass alcohol lamp and a precision 0–100°C by 0.2°C thermometer. The double-wall design of the steam jacket assures uniform temperature steam around the thermometer with no radiative effects.
The catalog scan is from : The Welch Scientific Company. Welch Laboratory Apparatus, 1968 Edition. Skokie Illinois ((1968), p 153. An image and short description of the double-walled steam jacket on our example is seen on a catalog scan from p160 of the same catalog showing the apparatus as part of a calorimeter setup.
© R. Paselk
Last modified 17 September 2013