Whether incited by the work of the French or not, we do not know, but in
the early part of this century the English began to do more work upon the
establishment of a standard, and in 1816 a commission was appointed by the
crown to examine and report upon the standard of length. Capt. Kater made a
long series of careful observations determining the second pendulum to be
39.1386 inches when reduced to the level of the sea. This measurement was
made on a scale made by Troughton--who, by the way, was the first to
introduce the use of the microscope in making measurements--under the
direction of and for Sir Geo. Schuckburgh. In 1822, having made three
reports, after many tests, it was recommended that the standard prepared by
Bird in 1760, marked "Standard Yard, 1760," be adopted as the standard for
Great Britain.
The act of June, 1824, after declaring that this measure should be adopted
as the standard, reads in Sec. III.: "And whereas it is expedient that the
Standard Yard, if lost, destroyed, defaced or otherwise injured should be
restored to the same length by reference to some invariable natural
Standard; and whereas it has been ascertained by the Commissioners
appointed by His Majesty to inquire into the Subjects of Weights and
Measures, that the Yard, hereby declared to be the Imperial Standard Yard,
when compared with a Pendulum vibrating Seconds of Mean Time in the
latitude of London, in a Vacuum at the Level of the Sea, is in the
proportion of Thirty-six Inches to Thirty-nine Inches and one thousand
three hundred and ninety-three ten thousandth parts of an Inch; Be it
enacted and declared, that if at any Time hereafter the said Imperial
Standard Yard shall be lost, or shall be in any manner destroyed, defaced
or otherwise injured, it shall and may be restored by making a new Standard
Yard bearing the same proportion to such Pendulum, as aforesaid, as the
said Imperial Standard Yard bears to such Pendulum."
It was not long after this act had been passed, if indeed not before, that
it became known that the pendulum method was an incorrect one, as it was
found that errors had occurred in reducing the length obtained to that at
the sea level, and despite the great pains that had been taken, it is
doubtful if the method was not faulty in some of its other details.
When the Houses of Parliament were burned in 1834, an opportunity was
offered to try the method upon which so much time and care had been spent.
A commission was appointed and to Sir Francis Baily was assigned the task
of restoring the standard. He did not live to complete the task, dying in
1844. He succeeded in determining the composition of the metal that was
best adapted to be used, which metal is now known as Baily's metal.
Public-domain text, read in full here on John Shaqi.
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