Elementary arithmetic, with brief notices of its history... by Robert Potts.

WEIGHTS AND MEASURES.

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bear them away as trophies from the valour, the patriotism, and the
virtues of a nation enlightened in its interests, its honour, and its
rights. But if an earthquake should swallow them up, or if it were
possible that a terrific blast of lightning should fuse the metal which
is the conservator of this measure, it will not therefore follow, citizen
legislators, that the fruit of so many labours, that the general type
of our measures, shall be lost to the national glory and the public
benefit."
On the grand question of an international system of weights and
measures, the British Government at that time appears not to have
appreciated the lofty aims of the Constituent Assembly of France;
notwithstanding its professions of being "so renowned for its feelings
as to the government of nations and the general welfare of mankind."
A motion, however, was made on the question in the House of Commons, but no further steps appear to have followed the motion.
It was not before the year 1837 that the metric system was made
legal in France, but then so as not to be brought into use before 1840.
It has been affirmed that the adoption of the system had been postponed chiefly from political motives, and by the hatred which attached
to everything connected with the Revolution. In some districts in
France at the present day, and even in Paris, the ancient measures
have not yet been wholly superseded.
In 1798 an account of some endeavours to ascertain a standard of
weight and measure by Sir George Shuckburgh Evelyn was printed in
the Transactions of the Royal Society. He states that in 1780 he had
taken up the idea of an universal measure from whence all the rest
might be derived by means of a pendulum with a moveable centre of
suspension. It appears that Mr. Whitehurst, F.R.S., published a
pamphlet in 1787, in which he described a method of finding an invariable length. The mechanism he employed consisted of a pendulum of variable length, which was kept vibrating by means of clockwork. The standard measure of length he defined to be nothing
more than the difference of the lengths of two pendulums, which
vibrate in different but ascertained times. Sir G. S. Evelyn obtained
the use of this machine, and having ascertained that the difference between the pendulum which vibrates 42 times, and that which vibrates
84 times in a minute, is equal to 59-89358 English inches, he made use
of that length for the determination of a standard of length.
To ascertain a standard of weight he provided microscopes and
micrometers for the most exact observations; a hydrostatic balance,
which when loaded with six pounds had its equilibrium disturbed by
the hundredth part of a grain; a solid cube of brass, whose edge was
five inches; and a solid brass cylinder, whose length was six inches
and diameter of the base four inches. He employed pure distilled
water, and weighing the cube in air and in water he found the weight
of a volume of water equal to the volume of the brass cube. The
same operation was performed with the brass cylinder, and on comparing the results of these two, and by other experiments, he determined the weight of a certain volume of distilled water to a very
great degree of accuracy.
The two results arrived at by these experiments may be thus
briefly expressed:-The difference of the lengths of the two pendulums vibrating 42 and 84 times in a minute of mean time, in the
latitude of London, at 113 feet above the level of the sea, at 60~ of