A bathometer (also bathymeter) is an
instrument for measuring water depth. It was previously used mainly in
oceanographical studies, but is rarely employed nowadays. The term originates from
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''βαθύς'' (''bathys''), "deep" and ''μέτρον'' (''métron''), "measure".
History
The earliest idea for a bathometer is due to
Leon Battista Alberti
Leon Battista Alberti (; 14 February 1404 – 25 April 1472) was an Italian Renaissance humanist author, artist, architect, poet, priest, linguist, philosopher, and cryptographer; he epitomised the nature of those identified now as polymaths. H ...
(1404–1472) who sunk a hollow sphere attached to some ballast with a hook. When the ball reached the bottom it detached from the ballast and resurfaced. The depth was determined (rather inaccurately) by the time it took to surface.
Jacob Perkins
Jacob Perkins (9 July 1766 – 30 July 1849) was an American inventor, mechanical engineer and physicist. Born in Newburyport, Massachusetts, Perkins was apprenticed to a goldsmith. He soon made himself known with a variety of useful mechanical i ...
(1766–1849) proposed a bathometer based on the compressibility of water. In this instrument the movement of a piston compressing a body of water enclosed in its cylinder is dependent on the pressure of the water outside the cylinder, and hence its depth. The amount the piston moved can be measured when it is returned to the surface.
A bathometer that did not need to be submerged was invented in 1876 by
William Siemens
Sir Carl Wilhelm Siemens (4 April 1823 – 19 November 1883), anglicised to Charles William Siemens, was a German-British electrical engineer and businessman.
Biography
Siemens was born in the village of Lenthe, today part of Gehrden, near Ha ...
, stimulated by the needs of the
telegraph industry. Siemens' instrument was the first to come into widespread use and is so different and so much more practical than anything that had gone before that he is often credited as the inventor of the bathometer. His instrument consisted of a tube of mercury and worked similar to a
barometer
A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...
. The pressure of the mercury acting under the force of gravity pushed down on, and deformed, a thin steel sheet. The height of the mercury in the column was thus proportional to the strength of the Earth's gravity field. The theory of the instrument was that the greater the depth of water under the ship, the lower the gravitational force would be. This is because water has a much lower density than the rocks of the Earth's crust. Starting in the mid-nineteenth century,
submarine telegraph cable
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried tel ...
s were being laid around the world. Accurate knowledge of the depth of the ocean bed was important for this work. Previously, depth was determined by taking
soundings with a lead line, a time-consuming and difficult method.
[* Jeffrey L. Kieve, ''The Electric Telegraph: A Social and Economic History'', p. 238, David and Charles, 1973 .]
See also
*
*
*
Sources
{{reflist
Scientific instruments
Oceanography
19th-century inventions