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

18

WEIGHTS AND MEASURES.

and two corresponding measures of capacity, the natural standard of
which is the difference between the specific gravities of wheat and wine.
To the French system there is only one unit of weight and one
measure of capacity, the natural standard of which is the specific
gravity of water. The French system has the advantage of unity in
the weight and in the measure, but has no common test of both; its
measure gives the weight of water only. The English system has the
inconvenience of two weights and two measures; but each measure is,
at the same time, a weight. Thus the gallon of wheat and the gallon
of wine, though of different dimensions, balance each other. A gallon
of wheat and of wine, each weighs eight pounds Avoirdupois."
" The litre, in the French system, is a measure for all grains and
for all liquids; but its capacity gives a weight only of distilled water.
As a measure of corn, of wine, or of oil, it gives the space which they
occupy, but not their weight. Now as the weight of these articles is
quite as important in the estimate of their quantities as the space
which they fill, a system which has two standard units for measures
of capacity, but of which each measure gives the same weight of the
respective articles, is quite as uniform as that which, of any given.article, requires two instruments to show its quantity-one to measure
the space it fills, and another for its weight. In the difference between
the specific gravities of corn and wine, nature has also dictated two
standard measures of capacity, each of them equiponderant to the
same weight. This diversity existing in nature, the Troy and
Avoirdupois weights, and the corn and wine measures of the English,system, are founded upon it. In Ealgland it has existed as long as
any recorded existence of man upon the island; but the system did
leot originate there, neither was. Charlemagne the author of it. The
weights and measures of Greece and iRome were founded upon it. The
LRomans had the mina and the libra, the nummulary pound of 12
ounces, and the commercial pound of 16. The Avoirdupois pound
came through the Romans from the Greeks, and through them, in all
probability, from Egypt (or Tyre). Of this there is internal evidence
in the weights themselves, and in the remarkable coincidence between
the cubic foot and the 1000 ounces, Avoirdupois, of water, and between
thie ounce, Avoirdupois, and the Jewish shekel; and if the shekel of
Abraham was the same as that of his descendants, the Avoirdupois
ounce, &c., may, like the cubit, have originated before the flood."
" The result of these reflections is, that the uniformity of nature for
ascertaining the quantities of all substances, both by gravity and by
occupied space, is a uniformity of proportion, and not of identity; that
instead of one weight and one measure it requires two units of each,
~proportioned to each other; and that the English system of metrology,
possessing two such weights and two such measures, is better adapted
to the only uniformity applicable to the subject, recognised by nature,
than the new French system, which, possessing only one weight and
one measure of capacity, identifies weight and measure only by the
single article of distilled water; the English uniformity being relative to the things weighed and measured, and the French only to the
in8strume)nnts used for weight and mensuration. The habits of every
individual inure him to the comparison of the definite portion of his
person with the existing standard measures to which he is accustomed.
There are few English men but could give a yard, a foot, or inch
measure from their own arms, hands, or fingers with great accuracy.