Conference Generale des Poids et Mesures : CPGM
The Conférence Générale des Poids et Mesures (General Conference on Weights and Measures or CGPM) is one of the three organizations established to maintain the SI system under the terms of the Metre Convention (1875). It meets in Paris every four to six years. In 2002 the CGPM represented 51 member states and ten further associate members. [1]
CGPM Meetings
- 1st (1889) - kilogram defined as mass of the international prototype kilogram (IPK) made of platinum-iridium and kept at the International Bureau of Weights and Measures, Sèvres, France. International prototype metre sanctioned.
- 2nd (1897)
- 3rd (1901) - use of kilogram for force or weight prohibited. Litre redefined as volume of 1 kg of water.
- 4th (1907) - carat = 200 mg adopted.
- 5th (1913) - International Temperature Scale proposed.
- 6th (1921) - Metre Convention revised.
- 7th (1927) - Consultative Committee for Electricity (CCE) created.
- 8th (1933) - need for absolute electrical unit identified.
- 9th (1948) - ampere defined. Lowercase l adopted as symbol for litre.
- 10th (1954) - kelvin defined. International System of Units (metre, kilogram, second, ampere, Kelvin, candela) began.
- 11th (1960) - metre redefined in terms of wavelengths of light. Hertz adopted. New metric system given the official symbol SI for Système International d'Unités, the "modernized metric system".
- 12th (1964) - original definition of litre = 1 dm³ restored.
- 13th (1967) - second redefined as duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. Degree Kelvin renamed kelvin. Candela redefined.
- 14th (1971) - mole defined. Pascal, newton per square metre, siemens approved.
- 15th (1975) - peta- and exa- prefixes. Gray and becquerel radiological units.
- 16th (1979) - candela defined. Both l and L provisioanlly allowed as symbols for litre.
- 17th (1983) - metre redefined in terms of the speed of light, but keeps same length.
- 18th (1987) - conventional values adopted for Josephson constant, KJ, and von Klitzing constant, RK.
- 19th (1991) - new prefixes zetta-, yotta- and yocto-.
- 20th (1995) - supplementary SI units (radian and steradian) become derived units.
- 21st (1999) - new SI derived unit, the katal = mole per second, for the expression of catalytic activity.
- 22nd (2003) - forthcoming
References
[1] http://www.bipm.fr/enus/1_Convention/member_states.htmlPrideaux, J. Selby, Sir Stamford
Ornithology,' and edited the 'Naturalist's Library,' in 40/40.html">40 volumes, which
Entomology. Of these 40 volumes 14 were written by himself. In 1836 he
later, was transformed into 'Annals of Natural History,' but remained under
History of Selborne.' Sir W. Jardine was also joint editor of the
'Ichthyology of Annandale,' 'Memoirs of the late Hugh Strickland,'
from Ward, 'Men of the Reign,' and Cates, 'Dictionary of General
so-called species.html">species ought to be called varieties, which I fully expected;
the Continent (not that he gives his authority), but I do not make out that
will write again.
Down [23rd December, 1859].
My dear Hooker,
I received last night your 'Introduction,' for which very many thanks; I am
It was very good of you to send Naudin, for I was very curious to see.html">see it.
gives artificial selection, as well as a score of English writers, and when
certainly prove exactly the same as mine. But I cannot find one word like
brings in his principle (page 103) of finality (which I do not understand),
which adapts the forms of every being, and harmonises them all throughout
formerly greater), that species were at first more plastic. His simile of
have reflected much on the subject, otherwise he would see that genealogy
closer approach to Wallace and me in Naudin than in Lamarck--we all agree
'Revue' in a few days (with the cover). I dare say Lyell would be glad.
On
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