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

12

WEIGHTS AND MEASURES.

thumb came to be considered as a part of the measure, and in process
of time an inch was substituted for it, so that a yard was made to
consist of 37 inches. This was recognised in 1404, in the reign of
IHenry IV., when it was ordered that the yard was to have an inch
added to it, containing the breadth of a man's thumb.
An Act of 10 Anne, in 1711, directed that each yard of cloth:should in measurement have one inch added to it " instead of that
which is commonly called a thumb's breadth." There were besides
different regulations ordered in different counties for different kinds of,cloth, both of linen and of wool. Nothing is prescribed by the laws
respecting any particular temperature at which measures are to be
'employed, the effect of any difference being too inconsiderable to be
perceived in any common case; but the state of dryness and moisture
is by no means indifferent to the result, and particular directions have
been given in many statutes respecting the effect of wetting cloth on
the measure of its length and breadth.
In 1790, the Constituent Assembly of France, on the proposition
of 1M. Talleyrand, agreed to invite the British Government to concur
with the French nation on fixing a natural unit of measures founded
on the length of the seconds pendulum in the latitude of 45~. A,Commission of Members of the Academy of Sciences was appointed,
and their report appeared in the following year.
Delambre and his colleagues, after much interruption, completed
their operations in 1796. A Commission of Members of the Institukte
was appointed to inspect and revise the recorded observations and
calculations, as well as the instruments employed in the course of the,operations. The Commission determined the lengthl of the metre
from the quadrant of the meridian to be equal to 443-295936 lignes,
being less than the metre provisoire (which was founded on La
Caille's measure of a degree of the meridian in the latitude of fortyfive degrees) by *146 of a ligne.
The subsequent determination of the unit of weight, the Idlogramme or decimetre cubed of distilled water, was made at its
greatest density, and not, as it was at first proposed, at the temperature
of melting snow.
On 19 Aug. 1798, the original metre and kilogramme were presented, with a pompous address, to the two Councils of the Legislative
Body of France: "This unit" (the metre), say they, "offers also one
aspect which is not without interest. It must be pleasing to the
father of a family to say, 'The field which supports my children is
such a portion of the globe. I am in this proportion co-proprietor of
the world.' " And further noticing that these prototypes shall bo
deposited among the national archives, to be preserved with religious
care; and that "the ignorance and ferocity of barbarians shall never
1 They proeposed that the ten-millionth part of the quadrant of the meridian.should be called the metre, and be considered as the unit of the new metrical system
of France.
That in order to determine the metre, an arc of the meridian extending from
Dunkirk to Barcelona, six degrees and a half to the north, and three degrees to the
south of the mean parallel of forty-five degrees, should be measured.
That the quadrant should be divided into one hundred degrees, the degree into
one hundred minutes, and the minute into one hundred seconds.
That the weight of a decimetre cubed of distilled water at the temperature of
melting ice should be determined as the unit of measures of weight.
That the subdivisions of all measures should be adapted to the decimal scale.