:: From the metric system to the international system::
The missions of the Conservatoire Des Arts Et Métiers
The
Institute for Metrology and Technology which is attached to the Ministry for
Agriculture and Trade, did not have the means necessary to the operations
and the studies that comparisons between weights and measures demanded. The
government had to create special committees when it was necessary. It
resorted to members of the Institute, teachers from the School of Technology
and Engineering or technicians.
After
the legal obligation came into force in 1840, the government thought it
necessary to designate an organism which would be entrusted with this kind
of operations, and it chose the School of Technology and Engineering. The
School director received a ministerial order in April 1848. It said that
"For the sake of science and industry, the central prototype standards
repository which is established at the Ministry for Agriculture and Trade
will be transferred to the School of Technology and Engineering, and will be
placed under the direction and surveillance of the School."
Concerning
the exchanges of standards that began in 1841, the order added, concerning
checking and comparing that "this task, which was to be executed under the
patronage of a Scientific Commission, must be continued under your personal
direction." From the following month - May 1848 - the models, standards and
instruments that were preserved in the Ministry "Weights and Measures
Gallery" were moved to the School of Technology and Engineering.
The
School sent a complete collection of weights, measures and weighing
instruments to the World Exhibition that took place in London in 1851. It
had order the collection to Parent, a mechanic who worked with screw
presses. From these times on, the metric system advantages were more and
more universally appreciated thanks to the relationships that the 1851, 1855
and 1862 world exhibitions established between scientists and engineers. The
comparisons that were demanded to the School were all the more important
since it dealt often with standards which were to become national
prototypes.
Processes
were run with the School's platinum standards. At its request, this
standards were subjected to a new comparison with the Archives standards in
1864. Thus, it was possible to work with all the indisputable results from
the School operations.
From
1867 to 1869, the School reviewed the standards that depended to the weights
and measures checking offices. The 371 offices had got metre, kilogramme and
litre standards, adjusted with a one-hundred-thousandth accuracy for lengths
and weights, and a ten-thousandth accuracy for capacities, which widely
exceeded local needs.
In
1869, when France was to suggest a meeting of an International Commission on
measures, fourteen states had received, thanks to the School, standardized
metric measures.
The
works of the Metre International Commission in 1870 and 1872 took place in
the School. They were led by the General Morin, a membre of the Institute
and the School's director. Tresca, the assistant director, lent a very
active support to these works too. Among others, he developped the X-profile
which was adopted for the international metre in 1889.
The
School's workshops also tried to melt many platinum-iridium alloys. In may
1874, they got a 250 kg casting of an alloy which was known as "the School's
alloy". It was not kept for the international prototypes because it did not
respect the allowances regarding the presence of some impurities and because
there was too much iridium. It is an alloy made by Johnson-Matthey, from
London, that was chosen. However, the national meters that were made of the
School's alloy were later considered as stable as the ones made of the
London alloy.
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