Standard Measures of United States, Great Britain and France History and actual comparisons. With appendix on introduction of the mètre

STANDARD MEASURES OF UNITED STATES, GREAT BRITAIN, AND FRANCE.

HISTORY AND ACTUAL COMPARISONS.

WITH APPENDIX ON INTRODUCTION OF THE MÈTRE.

BY ARTHUR S. C. WURTELE, ASS’T ENG., N. Y. C. & H. R. R.

E. & F. N. SPON, NEW YORK: 44 MURRAY STREET. LONDON: 16 CHARING CROSS. 1882.

COPYRIGHT, 1882, BY ARTHUR S. C. WURTELE.

INTRODUCTION.

During the preparation of this investigation of Standard Measures a large number of authorities were examined, including the following: Kelly’s “Universal Cambist,” Maunder’s “Weights and Measures,” “Encyclopædia Britannica,” “Chambers’ Encyclopædia,” Williams’ “Geodesy,” Hymer’s works, “Smithsonian Reports,” “Coast Survey Reports,” Herschel’s “Astronomy,” etc. The only concise and clear statement I found was J. E. Hilgard’s report to the Coast Survey on standards in 1876, which I was gratified to find coincides with my deductions.

ARTHUR S. C. WURTELE.

ALBANY, November 26, 1881.

STANDARD MEASURES.

A standard measure of length at first sight appears to be very simple--merely a bar of metal of any length, according to the unit of any country; and comparisons of different standards do not seem to present any difficulty. But on looking further into the thing, we find that standards are referred to some natural invariable length, and we are at once confronted with a mass of scientific reductions giving different values to the same thing, according to successively improved means of observation. We find, also, that comparisons of one standard with another differ, as given by reductions carried to great apparent exactness.

Every author appears to assume the right of using his own judgment as to what reduction is to be considered the most exact, and the result is a very confusing difference in apparently exact figures, with nothing to show how these differences arise.

I have endeavored to indicate what may be the cause of this confusion by giving the figures of actually observed comparisons and reductions; in a manner, the roots of the figures used as statements of length.

Sir Joseph Whitworth gives 1/40000 of an inch as the smallest length that can be measured with certainty, with an ultimate possibility of 1/1000000 of an inch; but imperceptible variations of temperature affect these infinitesimal lengths to such an extent that he believes the limit can only be reached at a standard temperature of 85° F., to avoid the effect of heat of the body.

It appears to me that comparisons should be made of double yards and mètres with the old French toise, as the limit of exactness would be thereby doubled.

Another great defect in statements of relative values is the omission of necessary facts--the material of which the bars or standards are made, the temperature at which comparison was made, and the standard temperatures used as to the final reduction, with the coefficient of expansion adopted.

Again, bars of different metals appear in time to sensibly change their relative length.

ENGLISH STANDARDS OF LENGTH.

The first establishment of a uniform standard appears to have been made in 1101 by Henry I., who is said to have fixed the ulna (now the yard) at the length of his arm; but nothing definite was done till 1736, when the Royal Society took steps toward securing a general standard, and in 1742 they had a standard yard made by Graham from a comparison of various yards and ells of Henry VII. and Elizabeth, that were kept in the Exchequer.

Two copies of the Royal Society standard yard were made by Bird in 1758 for a committee of Parliament, one of which was marked “standard of 1758,” and the other 1760. But no exact legal standard was yet established, as shown by comparisons in 1802 of the various standard measures in use which Pictet, of Geneva, made with an accurate scale by Troughton, using means exact to the ten thousandth part of an inch, with the following results at the temperature of 62° F.:

Troughton Scale 36·00000 inches. Parliamentary Standard (1758, Bird) 36·00023 “ Royal Society “ (1760, “ ) 35·99955 “ “ “ (Graham) 36·00130 “ Exchequer “ 35·99330 “ Tower “ 36·00400 “ Gen. Roy “ (Trig. Survey) 36·00036 “

Parliament finally undertook to reform the measures of England, and appointed a commission in 1818, under whose authority Capt. Kater compared the standard yards then in use with the following results, as referred to the Indian Survey standard:

Col. Lambton Standard (Indian Survey) 36·000000 inches. Bird’s Standard (1760) 36·000659 “ Sir Geo. Schuckburgh’s Standard 36·000642 “ Ramsden’s Bar. Ordnance Survey 36·003147 “ Gen. Roy’s Scale 36·001537 “ Royal Society Standard 36·002007 “

The commission reported in favor of adopting Bird’s standard of 1760, as it differed so slightly from Sir George Schuckburgh’s standard (which had been used in deducing the value of the French mètre) that those values could be assumed as correct. They also established the length of the seconds pendulum at level of sea in London and in vacuo as 39·13929 inches. The seconds pendulum had been previously fixed by Wollaston and Playfair in 1814 as 39·13047 inches.

On this report, an Act of Parliament in 1823 declared the only standard measure of length for the United Kingdom to be the yard as given by the distance at 32° F. between two points in gold studs on the brass bar, made by Bird, and marked “Standard of 1760,” and in the keeping of the Clerk of the House of Commons; also it referred this standard yard to the natural standard of a pendulum vibrating seconds of mean solar time at the level of the sea, in vacuo at London and temperature of 32° F., as in the proportion of 36 to 39·13929; so that a pendulum 36 inches long ought to make 90088·42 vibrations in 24 hours.

The Royal Society had a copy of the legal standard made by Bailey in 1834; and in the same year the Parliamentary standard was destroyed by fire at the burning of the Houses of Parliament, leaving the kingdom again without a legal standard.

All attempts made by a commission consisting of Airy, Bailey, Herschel, Lubbock, and Sheepshanks, to restore the standard by means of the seconds pendulum failed in exactness, on account of the many conditions of a vibrating pendulum, and recourse was had to the Royal Society standard, which had been carefully compared by Captain Kater in 1818, and from this in 1838 Bailey and Sheepshanks made six bronze bars, one inch square, and 38 inches long, which in 1855 were legalized by Act of Parliament, and the English standard of length defined as follows:

“That the straight line on distance between the centres of the transverse lines in the two gold plugs on the bronze bar deposited in the Exchequer shall be the genuine standard yard at the temperature of 62° Fahrenheit; and if lost, it shall be replaced by means of its copies.”

The French metrical system was made legal permissively in 1864, at the length established by Captain Kater, referred to in Act of Parliament of 1823, of 1 mètre equal to 39·37079 inches, or 3·28089916 feet.

These are the standards now in use in the United Kingdom.

UNITED STATES.

By the Constitution of the United States Congress is charged with fixing the standard of measures (Art. 1, sec. 8); but as no enactment has been made by Congress, the standard yard in England, which was legal previous to 1776 in the Colonies, is the standard yard of the United States, and does not differ with the English standard yard.

Under resolution of Congress in 1830, Mr. Hassler was employed to examine the standards in use.

Considerable discrepancies were found, but the mean of all examined corresponded very nearly with the English standard, and in 1832 the recommendation of Mr. Hassler was adopted, and the standard yard defined as the distance between the 27th and 63d inch marks, at the temperature of 62° F., on the brass scale 82 inches long, being an exact copy of Sir George Schuckburgh’s standard, made by Troughton, of London, for the Coast Survey, and deposited in the Office of Weights and Measures at Washington.

In 1836 an Act of Congress ordered standards to be sent to each Governor of a State, and the work was done under direction of Mr. Hassler.

In 1856, two copies of the English standard yard, as restored after destruction of the original standard by fire in 1834, No. 11 of bronze, and No. 57 of Low Moor wrought iron, were presented to the United States by Airy.

The United States Troughton standard bar being compared with No. 11 was found to be longer by 0·00085 inch, or in proportion of 1 to 1·0000237216, about 1½ inches in a mile, according to Report of Secretary of Treasury in 1857.

Later comparisons made by J. E. Hilgard, of the Coast Survey, at the British Standards Office, between No. 11 and the standard imperial yard, give No. 11 as 0·000088 inch shorter, or it would be of standard length at temperature of 62·25° F.

We may infer that the Troughton standard is too long by 0·000762 inch, or would be standard length at temperature 59·77° F. instead of at 62° by making expansion reduction with Airy’s coefficient for the bronze of the imperial standards, 0·000342 inch per yard for 1° F.