The Metric System [pp. 174-185]

The Metric System.
had recently set us a laudable example in
the great pains and labor taken in the execution of a new set of standard weights and
measures of superioraccuracy and precision."
(Mem. Roy. Ast. Soc., Vol. IX.)
The contingency contemplated by the last
clause of the Act of I824 actually happened
in less than ten years after its passage; for
the standards were lost, or irremediably injured, in the great fire which destroyed the
Houses of Parliament in October, i834. It
was then discovered that the restoration of
the lost standard yard could not be effected
with tolerable accuracy by means of its ratio
to the length of the second's pendulum at
London, as prescribed by the Act. For Captain Kater's measurement was subsequently
found to be incorrect, owing to the neglect
of certain precautions in determining the
length of the pendulum, which more recent
experiments have shown to be indispensable.
On account of these sources of error, the
yard could not be restored with certainty
within one five-hundredth of an inch; an
amount which, although inappreciable in all
ordinary measurements, is an intolerable error in a scientific standard.
Fortunately, early in I8.34 (hardly six
moiths before the destruction of the standards), Mr. Baily had executed a most laborious and minute comparison of the different
standard measures with a new scale constructed for the Royal Astronomical Society.
Thus the length of the legal standard, as
nearly as it could be determined, is known
in terms of this scale; and may, therefore,
be recovered, but not in the manner prescribed in the legislative enactment.
The Commissioners appointed in I838,
"to consider the steps to be taken to restore
the lost standard," recommended in their report of December, 184I, the construction of
a "standard yard," and four "Parliamentary
copies," from the best-authenticated copies
of the "Imperial standard yard" which then
existed. These recommendations were adopted, and the restored standard yard was legalized by an act of Parliament in July, x855.
Under the provisions of this act, the standards were deposited in the office of the Ex VOL. VI.-I2.
chequer. But in i866, on the consolidation
of the Office of Exchequer with the Audit
Office, and the creation of the Standards
Department of the Board of Trade, the custody of the " Imperial Standards "was transferred to the Warden of the Standards Department. They are now deposited in a fireproof iron chest in the strong room in the
basement of the Standards' Office. Copies
have been deposited at the royal mint and at
the royal observatory at Greenwich. Thus
the present British standard of length remains virtually the same as prescribed by
the Act of i824.
The legislation in i855 changed the standard of weight from the Troy pound of 5,760
grains, to the Avoirdupois pound of 7,00o0
grains; but did not abolish the Troy weight
and the Apothecaries' weight.
The legislation of I824 changed the standard of capacity from the wine gallon of
231 cubic inches to the "imperial gallon" of
27 7.274 cubic inches. This is equivalent in
weight to ten pounds avoirdupois of distilled
water at sixty-two degrees, Fahrenheit. In
like manner, the bushel equaling eight gallons
was changed from the Winchester bushel of
2, I50.42 cubic inches, to the Imperial bushel
of 2,21 8. 192 cubic inches. The Act of i85 5
did not disturb these measures of capacity.
The actual standard of length of the
United States is a brass scale of eighty-two
inches in length, prepared for the United
States Coast-Survey by Troughton, of London, in i8I3, and deposited in the Office of
Weights and Measures at Washington. The
temperature at which this scale is a standard
is sixty-two degrees, Fahrenheit, and the
standard yard is the distance between the
twenty-seventh and the sixty-third inches of
the scale. It was intended to be identical with
the British standard yard; and should be so
regarded. From a series of careful comparisons of this scale, executed in 7856 by Mr.
Saxton, under the direction of the late A.
D. Bache, with a bronze copy of the British
standard yard, it was found that the British
standard is shorter than the American yard
by o.ooo87 of an inch- a quantity by no
means inappreciable. Hence:
1885.]
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