P Adie Kew Pattern Mercury Marine Barometer
P Adie Kew Pattern Barometer
This is a Kew pattern mercury marine barometer made by the firm P Adie of the UK. I'm not sure of it's age, my estimate is it was made sometime between 1920 and 1936. The brass plaque on it says 1885, but 1885 may be the year the firm of P Adie was founded, as Patrick Adie died in 1886. The firm P Adie was at the Westminster address from 1874 to 1936. The plaque also says g=980.665 cm/s2. This value of g was not universally adopted until 1955. Prior to 1955, the values 980.665 and 980.62 were used on various barometers. The firm P Adie went out of business in 1942.
A Kew pattern barometer is a fixed cistern barometer. It was first designed in the latter half of the 1850s by John Welsh of the Kew Obsevatory and instrument maker Patrick Adie. Kew pattern barometers were favored for use in the UK, rather than the Fortin barometer, because they don't require the sensitive adjustment of mercury level in the cistern. This is an advantage particularly for shipboard use. The millibar scale on the barometer is permanently calculated to compensate for the fact that the mercury level in the cistern changes as the mercury level in the barometer tube changes. One disadvantage of the Kew barometer is that the accuracy of the barometer requires precise metering of the amount of mercury put in the barometer - this is not a factor for Fortin barometers. The Fortin barometer, though less convenient, is considered more accurate for laboratory determination of barometric pressure.
The barometer is of heavy brass construction, with a steel cistern. It is missing the glass tube and the thermometer. The barometer scale, in millibars, is cut into the brass tube rather than on a separate piece. The millibar was not adopted by the UK Met Office until 1914.
On the lower half of the barometer is the early version of the Gold Slide, which is a brass slide rule device for shipboard use, used to calculate the total barometric correction directly on the barometer. The early version has the temperature scale in degrees Kelvin. The user adjusts the sliding elements to the current latitude and the height of the barometer above the sea. The total barometric correction can then be read opposite the thermometer reading. Ernest Gold proposed the Gold slide in 1914. However, Gold slides were also retrofitted on earlier barometers. The Gold slide has the initials IMD on it. This is the Indian Meteorological Department.
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The barometer is of heavy brass construction, with a steel cistern. It is missing the glass tube and the thermometer. The barometer scale, in millibars, is cut into the brass tube rather than on a separate piece. The millibar was not adopted by the UK Met Office until 1914.
On the lower half of the barometer is the early version of the Gold Slide, which is a brass slide rule device for shipboard use, used to calculate the total barometric correction directly on the barometer. The early version has the temperature scale in degrees Kelvin. The user adjusts the sliding elements to the current latitude and the height of the barometer above the sea. The total barometric correction can then be read opposite the thermometer reading. Ernest Gold proposed the Gold slide in 1914. However, Gold slides were also retrofitted on earlier barometers. The Gold slide has the initials IMD on it. This is the Indian Meteorological Department.
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