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

~2 ~6 ~ WEIGHTS AND MEASURES.
quadrant of a meridian passing through Paris. It does so as regards
our actual legal standards of weight and capacity with much more
precision than the French system; and as regards that of length,
with still greater, and indeed with all but mathematical exactness.
"If the earth's polar axis be conceived divided into 500,000,000
inches, and a foot be taken to consist of 12 such inches, then 1-00 of
our actual legal imperial half-pints by measure, or 1000 of our
actual imperial ounces by weight of distilled water at our actual
standard temperature of 62~ Fahrenheit, will fill a hollow cube having
one such foot as its side. The amount of error in either case is only
one part in 8000.
4' The theoretical French metre is the ten-millionth part of the
elliptic quadrant above-mentioned; the theoretical litre is the thousandth of a cubic metre; and the theoretical gramme the millionth
of a cubic metre of distilled water at 320 Fahrenheit. The actual
error of the French legal or standard litre and gramme, or the
deviation of these standards as they actually exist from their true
theoretical value, is one part in 2730, and is consequently relatively
nearly three times as great as the error in our own standards of
capacity and weight, when referred to the earth's polar axis as their
theoretical origin in the manner above stated. Our actual imperial
measures of length deviate, it is true, by more than this amount from
their theoretical values so defined-that is to say, by one part in a
1000; so that a correction of one exact thousandth part subtracted
from the stated amount of any length in imperial measures suffices to
reduce it to its equivalent in such units as correspond to similar
aliquot parts of the polar axis. So corrected, the outstanding error
is only one part in 64000, The actual legal metre in use in France
is, however, not immaculate in this respect, its amount of error being
one part in 6400, which is ten times that which our British measures
so corrected would exhibit. British commerce extends, however to
Russia, British India, and Australia (besides North America), all of
them superior in area; and the two last at least of equal importance,
commercially speaking, with the totality of the metricised nations.
The Russian samgene is an exact multiple of the English foot. The
hath, the legal measure of length in British India, is 18 imperial
inches. The Australian system is identical with our own, as is also
that of North America. Taking into consideration this immense preponderance both in area, in population, and in commerce, we are not
only justified in taking our stand against this innovation, but entitled
to inquire if uniformity be insisted on; why, with an equally good
theoretical basis, to say the least, the majority is called upon to give
way to the minority."
The Act of 5 Geo. IV., e. 74, for the British imperial system of
weights and measures, being no rash act of legislation, is founded
on the experience of the past history of the English nation, and adapted
for the practical convenience and benefit of the community. The
French system was devised by their philosophers, who, having rejected all past experience, led by ideas, scarcely ever by facts, have
sacrificed every practical consideration to the idea of reducing the
divisions of all weights and measures to the denary scale of arithmetic.