r WEIGHTS and

MEASURES

STANDARDS

OF THE

C7 FTr^

E

a brief history

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Miscellaneous Pyblicataon 247
National Bureau of Standards

MAY 2 0 1954

U.S. Prototype Kilogram 20,

the standard of mass of the

United States.

U.S. Prototype Meter Bar 27,

the standard of length of the

United States from 1893 to

I960. On October 14, I960,

the meter was redefined in

terms of a wavelength of the

krypton 86 atom.
S. DEPARTMENT

F COMMERCE

fhcr H. Hodges, Secretary

MIONAL BUREAU

F STAN D ARDS

V. Astin, Director

EIGHTS and

MEASURES

STANDARDS

OF THE

a brief history

LEWIS V. iUDSON

NBS Miscellaneous Publication 247

Issued October 1963

(Supersedes Scientific Paper No. 17 and Miscellaneous Publication No. 64)

Fo^ sale by the Superintendent of Documents, U.S. Government Printing Office,

Washinston, D.C., 20402 - 35 cents
Preface

In 1905, Louis A. Fischer, then a distinguished metrologist on the stafF of the

National Bureau of Standards, presented a paper entitled "History of the Standard

Weights and Measures of the United States" before the First Annual Meeting of

the Sealers of Weights and Measures of the United States. This paper quickly came

to be considered a classic in its field. It was published by the National Bureau of

Standards several times—most recently in 1925 as Miscellaneous Publication 64.

For some time it has been out of print and in need of up-to-date revision. The

present publication covers the older historical material that Fischer so ably treated;

in addition, it includes a brief summary of important later developments affecting

the units and standards for length and mass. (Liberal use of Mr. Fischer's text is made in this publication.)

Lewis V. Judson .

iv
Contents

Page

Foreword m

Preface iv

1. Introduction 1

2. Early history of weights and measures in the United States 2

3. Units and standards 6

4. Early United States standards 6

5- Use of metric system officially permitted 10

6. International standards of weights and measures 13

7. The Mendenhall Order 16

8. Refinement of values for the yard and pound 20

9. Wavelength definition of the meter 21

10. Other definitions of units 21

11. Current and historical standards of length and mass at the National

Bureau of Standards 21

Appendix 1. Bibliography 25

Appendix 2. Report on the troy pound of the Mint 25

Appendix 3. The Mendenhall Order of April 5, 1893 26

Appendix 4. The international nautical mile 28

Appendix 5- The U.S. yard and pound 28

Appendix 6. Adoption of the wavelength definition of the meter 30

V

Weishts and Measures Standards of the United States

a brief history

Lewis V. Judson

A historical account is given of the standards of weights and measures of the United States from the time of the American Revolution through the year 1962. Current and historical standards of length and mass now in the possession of the National Bureau of Standards are listed and described.

1. Introduction

When a housewife buys a quart of milk, when a midwestern farmer sells his grain crop—in all present-day

commercial transactions—there is an implied faith

that as goods are exchanged for money there is the same just balance for buyer and seller. In the early

days of this country such faith was often lacking.

Great variation existed in the weights and measures

used in different localities, and even, at times, in

those used by different individuals in the same locality. The transition from this chaotic situation

to the present uniformity of weights and measures

has resulted from the establishment of accurate,

reliable national standards of length and mass and the

enactment of comprehensive weights and measures

statutes. The present highly precise, and extremely stable

national standards for these quantities were not

achieved overnight, or even in a decade. They are

the results of a long period of gradual evolution based

on the dedicated efforts of men who recognized the

growing need for accuracy of measurement. The

story of this development is an interesting one that

is of considerable historical importance, and is told

in the pages that follow.

696-760 O—63 2

In 1905, Louis A. Fischer, then Chief of the Metrology Division of the National Bureau of Standards,

presented a historical treatment of the United States

standards of weights and measures before the First

Annual Meeting of the Sealers of Weights and Measures of the United States. Although a great deal has

occurred in weights and measures since then, Fischer's

account has come to be considered a classic and will

be used freely in the present publication, either

verbatim or with such modifications as seem appropriate.

Fischer's paper was published first in the Proceedings of the First Annual Meeting of the Sealers

of Weights and Measures (now the National Conference on Weights and Measures), then published in

volume 1 of the Bulletin of the Bureau of Standards,

then as a reprint designated as Scientific Paper No. 17

of the Bureau of Standards, and finally as Miscellaneous Publication No. 64 of the National Bureau

of Standards, an illustrated edition of the address

designated as a memorial to Fischer. Even though

this last publication has long been exhausted, demands for it still continue, emphasizing the present

need for an up-to-date historical treatment.

1
The place of Louis A. Fischer in metrology has been

so ably described in the Foreword to Miscellaneous

Publication No. 64 that it is reproduced here verbatim.

As a matter of historical record, it is appropriate here to comment

briefly upon Mr. Fischer's career as a metrologist, which began with

his entry, in 1880, into the service of the Office of Standard Weights

and Measures of the Coast and Geodetic Survey. Starting in the workshop, where he was trained in the fabrication of precise standards, he served in all branches of the work up to the making of the most accurate determinations of length and mass, and by 1898 he was in immediate charge of the weights and measures office. When

the Bureau of Standards was established in 1901 that office was made

a part of the new bureau, and in the new organization became the

division of weights and measures of the Bureau of Standards. Mr.

Fischer was at once made chief of this division, a position which

he filled with conspicuous credit from that time continuously until

his death in 1921, except while on duty with the United States Army

during World War I. Throughout the nearly 20 years of his service with the Bureau of Standards, Mr. Fischer was prominently identified with every movement in the United States having to do with the science of metrology

or the supervision of commercial weights and measures. He became

one of the world's foremost experts in the comparison of funda- mental precision standards of length, his work at the International Bureau of Weights and Measures in the recomparison of certain meter bars being especially noteworthy and laying the foundation

for a thorough intercomparison of all national prototypes with

the international standard. Mr. Fischer's services during the World War were of inestimable

value. As technical advisor of the War Department in gauge stand- ardization he was in large measure responsible for the efficient manufacture and inspection of munitions in the many plants throughout

the country, by reason of his thorough practical knowledge of the

subject and the tireless energy he displayed in standardizing and

coordinating the manufacturing processes and the activities of thu hundreds of establishments engaged in this vital work.

Nor were his achievements less noteworthy in the more prosai(

field of supervision of the weighing and measuring devices used ii everyday commercial transactions. Appreciating as he did the fac that fundamental standards of precision mean but little to the busi ness life of a community until these standards are translated int accuracy at the merchants' counters, Mr. Fischer unceasingly de voted his energies to the task of developing efficient and comprehen

sive weights and measures supervision on the part of the severa

States and their local subdivisions, to which agencies the Congresj

has left the administration of this important function of govero ment. As early as 1905 he conceived the idea of an annual confeii ence of State and local officers charged with the control of weighi|[

and measures in their respective jurisdictions, and in that year calle; a meeting of such officers as were then engaged, directly or indirectlji in this work. This first meeting had a total attendance of but 1 persons, and it was before this small gathering that Mr. Fische delivered the paper which is published herewith, and which hi

since become the classic reference on this subject. From its humb

beginning, however, the Annual Conference on Weights and Mea

ures has grown until today it is truly national in its scope, and nun

bers among its members weights and measures officers from all par of the United States, as well as scores of others, representatives (

business and industry, who are interested in its objects and accoE plishments. With the Conference as one of the important mediuD

through which to work, Mr. Fischer was unceasing in his efforts carry to others his own firm conviction of the tremendous importam

to every community of adequate weights and measures supervisio

and to instill into those intrusted with the administration of weigh

and measures laws his own high ideals of the responsibility whii

is theirs and of the service which they should render. As a resui

it may truly be said that Louis A. Fischer is the father of what v know today as weights and measures control in the United Stall

Ik

2. Early History of Weights and Measures in the United States

Throughout its early history, the United States

Government showed extensive interest in uniform

weights and measures; several efforts were made to

secure international agreements in this field. This interest has continued through the years and is stronger

now than ever before.

The history of the original Confederation of States

and of the constitutional government of the United

States reveals much evidence of the perplexities arising

from the diversity of weights and measures among the

States and of the desirability of a uniform system.

The weights and measures in common use in this

country at the time of the American Revolution were

practically all of English origin and were intended to

be equivalent to those used in England at that period.

The principal units were the yard, the avoirdupois

pound, the gallon, and the bushel. More or less authentic copies of the English standards of the denominations mentioned had been brought over from

time to time and adopted by the different colonies.

Divergencies in these weights and measures wer

however, quite common, due no doubt to the fa

that the system of weights and measures of Englar

was not itself well established, and hence the copi

brought to this country were often adjusted to differe

standards.

That this condition was recognized very early

made evident by the Articles of Confederation, ratifi(

by the colonies in 1781, which contained the followii;

clause: "The United States in Congress assemb.

shall also have the sole and exclusive right and po\4

of regulating the alloy and value of coin struck

their own authority, or by that of the respecti^

States—fixing the standard of weights and measui]

throughout the United States— . . .

. " This povsfl

was transferred to Congress by the Constitution of ti: United States, effective 1789, in article 1, section

which reads: "The Congress shall have Power . To coin Money, regulate the Value thereof, and

foreign Coin, and fix the Standard of Weights a|

Measures."
• While Congress was not slow to take action in re- gard to coinage, it seems not to have been inclined to come to a decision in regard to weights and measures,

chough apparently willing enough to consider the

'subject. Washington, in his first annual message to Congress, January 1790,^ stated that "uniformity in

the currency, weights, and measures of the United

3tates is an object of great importance, and will, I am

!3ersuaded, be duly attended to." In accordance with

'\Vashington's suggestion, the matter was referred to

I select committee of the House of Representatives

,,vith instructions to prepare a bill, and it was also

ordered that the matter be referred to the Secretary of

kate to prepare and report to the House a proper plan

or establishing uniformity in the weights and measires.^ Jefferson was then Secretary of State, and in

esponse to the above request made a report, in which

le proposed two distinct plans. The first was subtantially to "define and render uniform and stable

he existing system * * * to reduce the dry and liquid neasures to corresponding capacities by establishing

[i single gallon of 270 cubic inches and a bushel of

ight gallons, or 2,160 cubic inches * * *." The

econd plan was "to reduce every branch to the same

f.ecimal ratio already established for coin, and thus

yring the calculations of the principal affairs of life vithin the arithmetic of every man who can multiply

nd divide plain numbers."^

: No action was taken, however, by the House and

ti his second message to Congress, on December 8,

790, Washington again called the attention of that

ody to the importance of the subject.* A few days

Iter the House ordered that the Jefferson report,

' iferred to above, be communicated to the Senate.

"')n March 1, 1791, the Senate committee to which the

'"latter had been referred reported that it would not be

'^fligible to make a change in the weights and measures,

5 a proposition had been made to the French and

' ritish Governments to obtain an international stand-

^'kd.^ This report was accepted and the matter

' ;sted there, although Washington, on October 25,

''791, repeated his former recommendations in his

''lird annual message to Congress, in the following

nguage:^

A uniformity in the weights and measures of the country is among

e important objects submitted to you by the Constitution and if it W'n be derived from a standard at once invariable and universal,

[t! ust be no less honorable to the public councils than conducive to

e public convenience.

^ Messages and Papers of the Presidents 1, p. 66.

. Congressional Register 3, p. 106. i Journal of the H.R., Childs & Swaine, p. 106.

jl Messages and Papers of the Presidents 1, p. 83.

* Jom-nal of the Senate, p. 143; John L. Fenno.

' Messages and Papers of the Presidents 1, p. 108.

A week later the Senate appointed a committee to

take into consideration the subject of weights and

measures. The committee reported on the 4th of

April 1792, recommending the adoption of the second

plan proposed by Jefferson, which was an entirely

decimal system. Again no definite action was taken.

The matter was considered in a desultory way by

Congress from time to time, but no agreement was

reached notwithstanding that the repeated recom- mendations of Washington were followed by those of

Adams. A sufficient explanation for the disinclination of Congress to act in a matter of such admitted

importance was the difficulty of agreeing upon a plan.

The fifth Congress, second session, in 1799, passed an

act ordering that the surveyor (of each port of the

United States) "shall * * * from time to time, and

particularly on the first Mondays in January and July

in each year, examine and try the weights, measures

and other instruments, used in ascertaining the duties on imports, with standards to be provided by each

collector at the public expense for that purpose; and

when disagreements and errors are discovered, he

shall report the same to the collector, and obey and

execute such directions as he may receive for correcting

thereof, agreeably to the standards aforesaid * * *." ''

This was the first act passed by Congress in regard

to weights and measures, but, in view of the fact that no standards had ever been adopted, the legislation

was not put into operation until about thirty-five

years after its passage, when certain standards, which

will be referred to later, were adopted by the Treasury

Department.

After the war of 1812 the question of uniformity in

weights and measures was again brought to the

attention of Congress, and in 1819 a committee of the

House of Representatives proposed to adopt absolute

standards conforming to the weights and measures in

common use; to obtain through a commission copies

of the yard, the bushel, the wine gallon, and the pound

supposed to conform to those in common use in the

United States; to preserve these standards and to distribute copies of them; to compare the length measure with the length of the second's pendulum

and also with that of an arc of the terrestrial meridian;

to connect them by determining the weight of a

certain bulk of distilled water, and to define the

bushel and the gallon by the weight of water which

they contain.^ No further record of the report is found, and it may be assumed that no action upon

it was taken. The Senate had, by a resolution adopted

March 3, 1817—two years prior to the above report

' statutes at Large 1, p. 643.

* Executive Doc. No. 73, 30th Cong., 1st sess., Senate.

3
John

Quincy

Adams,

1767-1848.

Ferdinand

Rudolph

Hassler,

1770-1843

(See also p. 6.

Original

troy pound

of the mint.

This weight was legalized by act of Congress, May 19, 1828, as the "standard troy pound of the mint" to regulate the coinage. It was displaced as the standard for the coinage by act of Congress,

March 4, 1911, when the "standard troy pound of the Bureau of Standards" was adopted for this purpose

requested the Secretary of State to prepare and report

a "statement" relative to the regulations and standards for weights and measures in the several States

and relative to the proceedings in foreign countries

for establishing uniformity in weights and measures,

together with such propositions relative thereto as might be proper to adopt in the United States. John Quincy Adams was at that time Secretary of

State, and four years later, on February 22, 1821, he

submitted an elaborate report to the House of Representatives in which he reviewed the history of weights

and measures in England, on the continent of Europe,

and in the United States. He considered in detail

the history of the metric system, and analyzed its merits and deficiencies. That system, a logical decimal system of weights and measures based upon

measurements of a quadrant of the earth's meridian

and the mass of a measured quantity of water, was

one of the new ideas resulting from the French Revolution.

The basic unit of the metric system as originally

conceived was to be a meter, a unit equal to one ten- millionth part of a quadrant of the earth's meridian

as measured from the North Pole to the equator

cube having sides of length equal to one-tenth of a meter was to be the unit of capacity, the liter, and

the mass of a volume of pure water equal to a cube oi one-tenth of a meter at the temperature of melting

ice was to be the unit of mass, the kilogram.

The necessary measurements and the constructioi

of standards was entrusted to committees ("commis

sions") composed of members of the Institute o

France ("Institut National des Sciences et des Arts"

and of deputies from other countries. The firs, undertaking was that of making extensive geodeti

and astronomical measurements along a meridia:

from Dunkirk to Barcelona using the toise, an ol

French unit of length equal roughly to 6 U.S. fee; and by modern measurements found to be equal t 1.949 090 meters, as the unit of length and computin,

the length of a quadrant of that meridian. Froli

these results there was constructed a one-meter bar (| platinum, the length of which was intended to

the one ten-millionth part of the length of the merifj

ional quadrant. This bar, having its length defia

by the distance between its two ends, became t

"Meter of the Archives."

Twelve iron copies of this meter bar were coil structed by a committee under the special direction (J

J. G. Tralles, the deputy from the Helvetic Republ

Two of these copies were assigned to Tralles, wl: then gave one, known in this country as the "Cor

mittee Meter," to his friend Ferdinand R. Has&

6

(1

151

lit

fi|

M

k

SJiat

Jtal

Jit

3)1 of

IftI

'ki, i

'* k

i

k

*{ecc

« att

4
!vh.o was selected by President Jefferson to be in

:harge of the Survey of the coast of the United States.

will be seen, this bar later played an important

)art in the weights and measures of this country.

After the Adams report had reviewed the status of

veights and measures at home and abroad, including

,n analysis of the advantages and disadvantages of

he metric system, it made a number of recommenations, the final ones being "1. To fix the standard,

v^ith the partial uniformity of which it is susceptible,

3r the present, excluding all innovation. 2. To

onsult with foreign nations, for the future and

Itimate establishment of universal and permanent

niformity."

As before. Congress took no action, probably

ecause the situation at that time was extremely

omplicated. Neither the metric system in France

or the system in common use in England was well

litablished. In France, the law making the metric

it^stem compulsory had been repealed, and the metric

'('stem was in use side by side with the ancient

'eights and measures, thus producing endless con-

'ision. In England the situation was not much

ttter; the ale gallon of 282 cubic inches and the wine

'allon of 231 cubic inches were both in use until

^24, when the new imperial gallon, containing

') pounds of water, and of a capacity of about 277}^

ibic inches, was adopted, together with the bushel

" 8 gallons. Neither of these measures was in use

L this country, and hence the United States could

)t at that time adopt either the system in use in

agland or the one in France without introducing

dical changes in the weights and measures already

use, nor was there at that time any positive as- rance that either the English or the metric system

'ould be permanent.

While Congress had been considering the matter,

est of the States had, independently of one another,

cured and adopted standards. Most of the standds thus adopted were brought from England; nevereless, standards of the same denomination differed

idely among themselves, thus perpetuating con5ion in the commerce between the States. Though confusion in commercial transactions

; ght be tolerated, uncertainty in regard to the

l inage could not be tolerated, and on May 19, 1828,

; certain troy pound was adopted as the standard for

linage by Congress in an "Act to continue the

Hnt at the City of Philadelphia, and for other

i rposes." Section 2 of this act reads as follows:

ind be it further enacted. That, for the purpose of securing a due

^|formity in weight of the coins of the United States * * * the

: ss troy pound weight procured by the minister of the United

i

States at London, in the year one thousand eight hundred and

twenty-seven, for the use of the mint, and now in the custody of

the Mint at Philadelphia, shall be the standard troy pound of the Mint of the United States, conformably to which the coinage

thereof shall be regulated.

The troy pound thus adopted had been procured in

1827 by Albert Gallatin, United States minister at London, and brought to this country by special

messenger, who delivered it to the director of the

Mint at Philadelphia. The weight was of brass and

an "exact" copy of the imperial troy pound of Great

Britain, according to the statement of Captain Kater,

who made the comparison between the two standards.

The casket and accompanying packages were retained

under seal until President Adams visited Philadelphia

and verified Gallatin's seal and the other facts in

regard to its authenticity.

This ceremony took place on October 12, 1827, and

the full certificate of President Adams in regard to

the seal, which he readily recognized, and to the

whole transaction and consequent accuracy of the

weight was added to the vouchers in the case. He

declared, in conclusion, his belief that the brass

weight then exhibited was the identical pound copy

of the imperial standard troy pound of Great Britain.

These facts were communicated to Congress through

Committee on the Mint and resulted in the passage of

the act cited above. This act was not modified until

83 years later, in 1911. A report of Samuel Moore on

the original troy pound of the Mint, giving many

interesting details, is reproduced in appendix 2. While the act of Congress of 1828 only made this

pound the standard for coinage, it virtually became

the fundamental standard of the United States from

which the avoirdupois pound in common use was

derived.

On May 29, 1830, two years after the mint pound

had been legalized for coinage, the Senate passed a resolution directing the Secretary of the Treasury to cause a comparison of the weights and measures in use at the principal customhouses to be made, and to

report to the Senate at its next session.

Steps were promptly taken by the Treasury Department to comply with the resolution of the Senate.

The preliminary report of F. R. Hassler, Superintendent of the Coast Survey, to whom the investigation

had been intrusted, was transmitted to the Senate on March 3, 1831; ^ a more complete report followed in

June 1832.

As was anticipated, large discrepancies were found

to exist among the weights and measures in use at the

different ports, some being too small and others too

9 See H.R. Doc. No. 299, 22d Cong., 1st sess.
large, but the average value of the various denominations agreed fairly well with the weights and measures

in use in Great Britain at the time of the American

Revolution.

Without waiting for authority from Congress the

Treasury Department took immediate steps to correct

the situation by having constructed, under Hassler's

direction, the necessary weights and measures for the

3. Units an

Before weights and measures could be constructed,

however, it was necessary for the Treasury Department

to decide upon certain units and to adopt standards,

that is, the material representatives of these units.

A clear understanding of the difference between

"units" and "standards" will aid the reader in the

sections that follow.

A unit is a determinate quantity (that is, one

established by definition) in terms of which values,

quantities, amounts, or magnitudes are expressed.

Being fixed by definition, a unit is itself independent

of physical conditions—as, for example, temperatureeven though it may be defined in relation to some

object that is affected by such conditions. Thus a

particular unit of capacity may be defined as a volume

of a specified number of cubic inches; the United

States gallon is so defined—as a unit of 231 cubic

inches. Or again, a particular unit of length may be

defined as a distance corresponding to the interval

between certain engraved lines on a certain metal bar

when measured under specified conditions, including

those of the support and the temperature of the bar;

until October I960 the meter unit was so defined in

relation to the international meter bar.

A stayidard is the physical embodiment of a unit.

In general a standard is not independent of physical

4. Early United

The units finally adopted by the Treasury Department in 1832 were the yard of 36 inches, the avoirdupois pound of 7,000 grains, the gallon of 231 cubic

inches, and the bushel of 2,150.42 cubic inches. The

standard yard adopted was the 36 inches comprised

between the 27th and the 63d inches of a certain brass

bar, commonly designated as an 82-inch bar, prepared

for the Coast Survey by Troughton of London.

Hassler had brought this bar to the United States in

1815, after he had been detained in Europe for several

years by the War of 1812. The 36-inch space referred

to was supposed to be identical with the English

standard at 62 °F, although it had never been directly

compared with that standard.

customs service. The divergencies among the;i weights and measures in use in the customs service ' were directly opposed to the spirit of the Constij

tution, which requires that all duties, imposts, andl

excises shall be uniform throughout the United States,"

and the Secretary of the Treasury felt fully authorizedi

in taking steps to secure uniformity when discrepan-'.

cies were found.

\ Standards

conditions and is a true embodiment of the unit only

under specified conditions. Thus a 1-gallon metal

standard will have a capacity of 1 gallon only when:

the standard is at a certain temperature; at any othen

temperature the capacity of the standard will have

been increased or decreased as a result of the expansion

or contraction of the metal caused by the temperature,

change. Or again, a length standard having a nomina]

value of one yard will have an actual value of one^ yard only when at one particular temperature anc when supported in a certain manner; a lowering of iti' temperature will cause the standard to shorten, £

raising of its temperature will cause it to lengthen

and a change of the manner in which it is supportec

may introduce a change in its length.

When a unit is defined in terms of a standard, the

latter acquires a fundamental character; the Interna

tional Prototype Meter was such a standard until the; meter unit was redefined in I960. Standards are clas:

sified into groups, according to their character, th(

order of their accuracy, and the order of their lega:

or other importance. Thus there are, for example

international and national

'

' prototypes,

'

' State

'

' refer

,

ence" standards, "laboratory working" standards

"field" standards, and various "classes" of standard:

estabhshed largely on the basis of design and accuracy:

States Standards

It is evident from Hassler's reports that he regardec!

the English yard as the real standard of length of th(

United States and the Troughton scale merely as j copy whose length should be corrected if it was sub

sequently found to differ from the English yard; am,

this view was taken by others who subsequently hac

charge of our standards, as will be shown later on. The avoirdupois pound adopted by Hassler as thi;

standard for the Treasury Department was derive(!

from the troy pound of the Mint according to th(

equivalent, 1 avoirdupois pound equals pound

troy. This was the accepted relation in this countr

as well as in England; hence both the troy and avoir

i« Article I, sec 8, clause 1.
Types of testing balances furnished to the

states.

Under the terras of an act passed in 1838 the Secretary of the Treasury was directed to furnish balances to the States. As furnished, a 'omplete set of these balances comprised a 50-pound balance, a medium balance of about 10 pounds capacity, and a small balance of about

-pound capacity. (See note 11, p 8.) These balances are on display at the National Bureau of Standards.

standards of length, mass, and capacity furnished to the States under the joint resolution of Congress of June 14, 1836.

^ In the illustration the half-bushel measure is at the upper left, the liquid measures—1 gallon to ji pint—at upper right; slicker plates are

1 position atop each of these capacity measures. The 13 weights at the left are troy standards. Avoirdupois standards are above and to

>he right of the troy weights. In the foreground are the yard and matrix. .7
dupois pounds adopted were in practical accord

with the similar standards of Great Britain.

The units of capacity, namely, the wine gallon of

231 cubic inches and the Winchester bushel of 2,150.42

cubic inches, were adopted because, as intimated, they

represented more closely than any other English

standards the average of the capacity measures in use

in the United States at the date of Hassler's investigation. The wine gallon was introduced as a wine

measure into England in 1707, during the reign of

Queen Anne, but it was abolished in 1824, when the

new imperial gallon, containing 10-pounds of water,

was made the standard. This last statement applies

also to the bushel of 2,150.42 cubic inches. This

bushel is the earliest English capacity measure of

which we have any record, a copy of it made by order

of Henry VII being still in existence. But this bushel

had also been abolished in England, it having been

superseded by the bushel of 8 imperial gallons.

Therefore neither the gallon nor the bushel adopted

by the United States Treasury Department was in

accord with the legal capacity standards of England,

but they were smaller by about 17 percent and 3 percent, respectively, and these differences exist at the

present time. Not only did they differ from the new

standards in Great Britain, but they also differed from

the discarded English standards from which they were

derived for the reason that Hassler selected the temperature of the maximum density of water as the temperature at which the United States measures were

standard, whereas their English prototypes were

standard at 62 °F. The numerical value in degrees

Fahrenheit of the temperature at which water has its maximum density was determined by Hassler to be

39.83 °F; later and more precise determinations have

shown this to be 39.2 °F.

Such, then, were the fundamental standards adopted

by the Treasury Department on Hassler's recommendation; and the weights and measures for the customs

service were constructed to conform to these. The

construction of the weights and measures for this

purpose was pushed with almost feverish haste, and

so well satisfied was Congress with the progress made

that the following resolution was passed and approved

June 14, 1836:

Resolved by the Senate and House of Representatives of the United States

of America in Congress assembled. That the Secretary of the Treasury be, and he hereby is, directed to cause a complete set of all weights and

measures adopted as standards and now either made or in progress

of manufacture for the use of the several custom-houses, and for

other purposes, to be delivered to the governor of each State in the

Union, or such person as he may appoint, for the use of the States,

respectively, to the end that a uniform standard of weights and

measures may be established throughout the United States.

8

While the resolution does not specifically adopt the;; standards described above, its practical effect was to make them the standards for the United States, inasmuch as the weights and measures distributed to the

States in accordance with the act were in almost every' case adopted by the State legislatures soon after theii. receipt.

By 1838 the weights for the States were reported

finished, and, during the following year, the weight;

for the customhouses were completed and delivered.^'

The resolution of 1836 was supplemented by Con ; gress by the act of July 7, 1838, an act having the

original purpose "to provide for the support of the Military Academy of the United States for the yea, 1838." One of several amendments to this act, how

ever, reads as follows:

That the Secretary of the Treasury cause to be made, under thi' superintendence of Mr. Hassler, one standard balance for each State and that when completed he cause them to be delivered to the re spective Governors for the use of the respective States.

It is interesting that under this authority balance;

in three capacities instead of one were built for th

States, a large (capacity 50 pounds), a mediun

(capacity about 10 pounds), and a small (capacit'

1 pound). A commentary on this departure from th

specific terms of the statute is found in House Docu

ment No. 159, 28th Congress, 2d Session; this doc

ument comprises a report dated February 26, 1845

by A. D. Bache, Hassler's successor as Superintenden

of Weights and Measures, on the progress made ii the construction of standard weights, measures and balances during the year 1844. Appended ti Bache's report, as appendix A thereto, is a specia:

report, dated January 4, 1844, made to the Secretar

of the Treasury by Edward Hassler, a son of F. E

Hassler, who had served for some years as his father'

assistant in the construction of weights, measures and balances. In this special report Edward Hassk

quotes that paragraph of the 1838 Act authorizin

the furnishing to each State of "one standard ba. ance," and then goes on to say:

The spirit of the above law is, that the States be furnished wr

means by which they will be enabled to determine any questic that may arise, with such a degree of nicety as to be as valuab'

for all practical purposes as if absolutely exact. This object cannot be secured by any single balance; consequent

arises the necessity of seeking the best means of accomplishing tl

desired object. Experience has proved that it cannot be secun with sufficient accuracy by less thau three balances. Consequently, I considered myself justified in carrying ont tl

spirit, and securing to the country the important and so-muc

needed object of the law.

" H.R. Doc. 159, 28tti Cong., 2d sess.
It is not clear from the records now available that

ach State received three balances, one of each

apacity, but it is known that this was the case in

ome States, and it is presumed that the normal

istribution was on the basis of three balances per

itate. By 1850 practically all the States admitted to the

Jnion had been supplied with complete sets of weights

nd measures, and, in addition, sets were presented

J England, France, Japan, and Siam. As new

rates were admitted they were also supplied with

;ts of standards, the last of these sets being supplied

o North Dakota in 1893. Two special sets of

tandards have since been prepared. One was pre-

;nted to the State of Alaska in 1959 and the other

resented to the State of Hawaii in I960.

A list of the weights and measures comprising one

f the original State sets is given below.

First. A set of standard weights composed of ne each of the following:

Avoirdupois weights

pounds ounces ounce ounce

50. . 8 0.05 0. 0005

25. . 4 0.04 0. 0004

20 2 0.03 0. 0003

10 1 0.02 0. 0002

5. .

12 0.5 0.01 0. 0001

4. .. 0.4 0.005

3. .. 0.3 0.004

2 0.2 0.003

1 0.1 0.002

0.001

froy weights

pound ounces ounce ounce

1 10 0.5 0.005

6 0.4 0.004

5 0.3 0.003

4 0.2 0.002

3 0,1 0. 001

2 0.05 0. 0005

1 0.04 0. 0004

0.03 0. 0003

0.02 0. 0002

0.01 0. 0001

(The avoirdupois and troy weights 0.05 ounce and

'nailer were made of silver wire.)

Second. A standard brass yard measure, with

latrix.

Third . A set of liquid capacity measures, consisting

12 The denominations of some of the weights were changed in sets supplied

ter 1857. Instead of decimal parts of the ounce, weights of the following inominations were furnished: \i ounce, K ounce, \^ ounce, and ^le ounce;

, 25, 10, 5, 4, 3, 2, 1, 0.05, 0.04, 0.03, 0.02, and 0.01 grains.

of one of each of the following, with its groundglass cover.

1 gallon

Yi gallon

1 liquid quart

1 pint

Vi pint

Fourth. A brass standard half-bushel with a ground glass cover.

In order to carry out the provisions of the resolution

of 1836 and the act of 1838 the Office of Weights and

Measures had been established under the direction of

the Superintendent of the Coast Survey. All the

standards adopted at the beginning of the work, and

subsequently, were in the charge of this Office, with

the exception of the troy pound of the Mint, which

remained at Philadelphia.

In October 1834, the British imperial yard and troy

pound made in 1758, of which the Troughton scale

and the mint pound were supposed to be exact copies, were destroyed by the burning of the Houses of Parliament. When the new imperial standards to replace

them were completed in 1855 two copies of the yard

and one copy of the avoirdupois pound were presented

to the United States, arriving in this country in 1856.

One of these bars, namely, bronze yard No. 11, was

very soon after compared with the Troughton scale,

the result showing that the accepted 36 inches of the

Troughton scale was 0.00087 inch longer than the

British imperial yard.'^ The second bar received from

England was subsequently compared with the Troughton scale and fully corroborated the result obtained

from the comparison with bronze No. 11. The new

yards, and especially bronze No. 11, were far superior

to the Troughton scale as standards of length, and

consequently they were accepted by the Office of

Weights and Measures as the standards of the United

States, and all comparisons were afterwards referred

to the imperial yard through these two standards.

They were twice taken to England and recompared

with the imperial yard, once in 1876 and again in 1888.

The avoirdupois pound presented with the two

yards was also compared with the United States

avoirdupois pound derived from the mint pound, the

result showing a very satisfactory agreement. The

advent of the new pound did not, therefore, disturb

the position of the troy pound of the Mint, or of the

avoirdupois pound derived from it. There is a refer- ence concerning this comparison of the pounds made

by Alexander D. Bache, Superintendent of Weights

and Measures, in a report dated December 30, 1856 to

13 See Report of the Secretary of the Treasm-y on the construction and

distribution of weights and measm'es in 1857. S. Ex. Doc. No. 27, 34th Cong., 3d sess.

696-760 0—63 3 9
the Treasury Department (34th Congress, 3d Session,

Senate Executive Document No. 27, p. 18):

The copy of the British standard commercial pouad was compared

with the American standard commercial pound—the weight used being that made by Mr. Hassler from the troy pound in the United

States mint, and marked with a star (commonly designated as the

star found^.

In the standards vault of the National Bureau of

Standards there is preserved a 1-pound avoirdupois

brass knob weight marked on the top surface of the

knob with a star. Although positive identification!

is not possible, it seems not unreasonable to assume

that this weight is the standard referred to in the,

Fischer and Bache texts. (See illustration p. 22.)

At present there is no United States national proto-'

type avoirdupois pound constituting the ultimate

national reference standard for avoirdupois standard;

of lower order. Laboratory sets of avoirdupoii;

standards are in use, but these are derived from the national prototype kilogram.

5. Use of Metric System Officially Permitted

The next and perhaps the most important legislation

enacted by Congress was the act of 1866 legalizing the

metric system of weights and measures in the United

States.

The act, which was passed July 28, 1866, reads as follows:

Be it enacted by the Senate and House of Representatives of the United

States of America in Congress assembled. That from and after the passage

of this act it shall be lawful throughout the United States of America

to employ the weights and measures of the metric system; and no

contract or dealing, or pleading in any court, shall be deemed invalid

or liable to objection because the weights or measures expressed or

referred to therein are weights or measures of the metric system. SEC. 2. And be it further enacted, That the tables in the schedule

hereto annexed shall be recognized in the construction of contracts, and in all legal proceedings, as establishing, in terms of the weights

and measures now in use in the United States, the equivalents of the weights and measures expressed therein in terms of the metric system;

and said tables may be lawfully used for computing, determining,

and expressing in customary weights and measures the weights and

measures of the metric system.

(See tables on facing page.)

While the above act was being considered. Congress

also considered a resolution authorizing the Secretary of

the Treasury to furnish the States with metric weights

and measures. Strange to say, this resolution, which

logically should follow, was approved one day

before the act legalizing the use of the metric system.

It was a joint resolution and read as follows:

Be it resolved by the Senate and House of Representatives of the United

States of America in Congress assembled. That the Secretary of the Treasury be, and he is hereby, authorized and directed to furnish

to each State, to be delivered to the governor thereof, one set of standard weights and measures of the metric system for the use of the States, respectively.

The work of making and adjusting these standards

fell naturally upon the Office of Weights and Measures, and the first matter to be resolved was the

choosing of the reference standards. The practice

followed by those countries that had adopted the

metric system of accepting the meter and the kilogram of the Archives of France as fundamental

standards was followed by the United States. The

question then was mainly one of securing authentii

copies of these standards. Fortunately the Office o Weights and Measures had several copies of botl

standards of more or less authenticity on hand

but without hesitation the iron bar known as th

"Committee Meter" and a platinum kilogram, know

as the "Arago Kilogram," were selected.

The committee meter has already been mentione

as being one of the copies of the meter of the Archive!

and thus a standard of considerable importance in th

metric system. As stated before, this bar is made oj iron, with a cross section of 9 by 29 mm, and its lengc

is defined by the end surfaces, which are remarkably

plane when one considers the age in which the ba; were made. The bar bears the stamp of the corj

mittee, namely, a small ellipse. Three quadran

of the ellipse are shaded and the fourth one clea

except for the number 10,000,000, which indicat

the number of meters in a meridian quadrant of tlj earth. In Hassler's report on the construction

the meters it is stated, on the authority of Trallei

that all the meters agreed with the true meter with

one-millionth part of the toise.'^ This is equiv|

lent to about two millionths of a meter, the toij

being equal to approximately 1.95 meters.

When Hassler came to the United States in ISj

he brought with him the committee meter, whi

he soon after presented to the American Philosophic]

Society of Philadelphia, Pa. Shortly after, when

was put in charge of the survey of the coast

meter was placed at his disposal by the Philosophicj

Society, and he made it the standard of length i| that work. Until 1890 all base measurements of ti Coast Survey were referred to this meter.''' Thus

was natural that this bar should be selected as ti standard to which the State meters should confoi

" H.R. Doc. No. 299, 22d Cong., 1st sess., pp. 75, 76.

IS The toise was the French standard of length prior to the adoption ofl meter, and all the geodetic measui'ements upon which the meter was b; were made with the toise. Its length is 1.949+meters.

i» Special Publication No. 4, U.S. Coast and Geodetic Survey.

10
MEASURES OF LENGTH

Metric denominations and values Equivalents in denominations in use

[yriameter 10,000 meters 6. 2137 miles. 1,000 meters 0. 62137 mile, or 3,280 feet and 10 inches. 100 meters 328 feet and 1 inch. 10 meters 393.7 inches.

1 meter 39. 37 inches. ecimeter .... J^lo of a meter 3.937 inches. i entimeter . . . }looofameter 0.3937 inch. 0.0394 inch.

MEASURES OF CAPACITY

Metric denominations and values Equivalents in denominations in use

Names

,;iloIiter or stere

.lectoliter :lekaliter Uter

.leciliter entiliter

'lilliliter

Number

of liters

1,000

100

10

1 Mo

Koo

Mooo

Cubic measure Dry measure

1 cubic meter

Yio of a cubic meter . . . 10 cubic decimeters . . . 1 cubic decimeter

}io of a cubic decimeter 10 cubic centimeters. . 1 cubic centimeter ....

1.308 cubic yards

2 bushels and 3-35 pecks

9.08 quarts 0.908 quart

6.1022 cubic inches. . . . 0.6102 cubic inch

0.061 cubic inch

Liquid or wine

measure

264.17 gallons. 26.417 gallons. 2.6417 gallons. 1.0567 quarts. 0.845 gill. 0.338 fluid ounce.

0.27 fluid dram.

MEASURES OF SURFACE

Metric denominations and values Equivalents in denominations in use

Hectare .... 10,000 square meters 2.471 acres.

.re 100 square meters 119.6 square yards.

.entare .... 1 square meter 1, 550 square inches.

WEIGHTS

Metric denominations and values Equivalents in denominations in use

Names Number of gramsWeight of what quantity of water at maximum density Avoirdupois weight

/lillier or tonneau

Quintal

t lyriagram

>ilogram or kilo. lectogram

dekagram

iram

)ecigram

j Centigram

vlilligram

1, 000, 000

100, 000

10, 000

1, 000

100

10

1 Ko

Moo Mooo

1 cubic meter

1 hectoliter 10 liters

1 liter

1 deciliter 10 cubic centimeters . . . 1 cubic centimeter Mo of a cubic centimeter 10 cubic millimeters. . . 1 cubic millimeter

2204.6

220.46

22.046 2.2046

3.5274

0.3527

15.432 1.5432

0. 1543 0.0154

pounds.

pounds.

pounds.

pounds.

ounces. ounce.

grains.

grains.

grain.

grain.

11
Metric standards of length, mass, and capacity, furnished to the States under the joint resolution of Congress of July

27, 1866.

In the illustration the liter (litre) and the dekaliter (decalitre) are at the upper left and center, each with a slicker plate in position. The weights are centrally positioned. In the foreground are two meter bars, the upper one a line standard and the lowei one an end standard.

International

Standard of Mass

INTERNATIONAL KILOGRAM

T

KILOGRAM 20

T

Calibrated at National Bureau of Standards

Calibrated in State Laboratories

NBS LABORATORY STANDARDS

(Metric and United States Customary)

STATE REFERENCE STANDARDS

STATE LABORATORY STANDARDS

STATE FIELD STANDARDS

I

United States National

Standard of Mass Cali- brated at International Bureau of Weights and

Measures

Calibrated at National Bureau of Standards

"L

CITY AND COUNTY STANDARDS

REGULATORY CONTROLS

12

Progression of standards.
The Arago kilogram was procured in 1821 by

Gallatin while minister of the United States to France

'and was sent to this country, together with a platinum meter. The certificate of Arago, the celebrated

physicist, which accompanied these standards, states

chat the kilogram differs from the original kilogram

bf the Archives by less than 1 mg. The weight is a platinum cylinder with flat bases, the edges being

slightly rounded. The height and diameter are

nearly equal, being approximately 39.5 mm each.

There is no stamp or distinguishing mark of any kind,

except near the center of one base there is a faint lathe

Dr tool mark of circular form, thus: O . The weight

is contained in a square mahogany box, on the cover

3f which is a circular silver plate bearing the inscription "Kilogramme compare pour son Poids a I'Etalon

Prototype des Archives de France, et verifie par M.

A-rago. Fortin fecit." (Kilogram compared for its

lA^eight with the prototype standard of the Archives

Df France, and verified by Mr. Arago. Made by

i-'ortin.) No particulars of Arago's comparison with

:he kilogram of the Archives were furnished, and

:onsequently it is not known what means he used in

naking his comparison nor whether he reduced his

A^eighings to vacuo. It was not until 1879 that the

\rago kilogram was compared with other standards

jf recognized authority. It is true that it was compared between 1852 and 1873 with two kilograms in

;he possession of the Office of Weights and Measures,

3ut as both of these weights were of brass and of

anknown density, no great reliance could be attached

:o the results. In 1879, however, it was taken to England and there compared with the British platilum kilogram in the custody of the Standards Office.

This comparison indicated that the Arago kilogram

A^as 4.25 mg light, but this result could not be con- ddered conclusive, on account of certain assumptions

nade in the reduction to vacuo and also in regard to

:he correction to the British kilogram.

In 1884 the weight was taken from the Standards

Dffice in London, where it had been since 1879, to the

nternational Bureau of Weights and Measures at

^'aris and there compared with two auxiliary kilograms whose values in terms of the kilogram of the

Archives were known with the greatest accuracy.

The result obtained from the comparison confirmed

that previously obtained from the comparison with

the British kilogram, the result giving

Arago kilogram = 1,000 g— 4.63 mg.

As the weights supplied to the States were to be

made of brass, it was more convenient to compare them

with a brass standard, and in order to do this two

secondary brass standards were carefully compared

between the years 1873-1876 with the Arago kilogram

and afterwards used in all the work of adjustment and

verification. One of the kilograms, known as the

Silbermann kilogram, was presented to the United

States by France in 1852, together with a number of

other weights and measures. The other kilogram

used was one made in the Office of Weights and

Measures and was identical in form and material with

the kilograms subsequently furnished to the States.

As the unit of capacity in the metric system is defined as the volume of the mass of 1 kilogram of

pure water at the temperature of maximum density,

the most convenient way to adjust such measures, and

in fact all capacity measures, is by weighing the

water they contain. The only two material standards that need to be considered, therefore, in connection with the metric weights and measures furnished to the States in accordance with the act of 1866

are the committee meter and the Arago kilogram

described above.

By the end of 1880 practically all the States had

been supplied with sets of metric weights and measures consisting of the following denominations:

[One brass line meter. Length measures ^ _ ,

, ° [One steel end meter. [One liter made of brass. Capacity measures S , , ,. , r, ^ [One dekaliter made or brass. One myriagram made of brass. One kilogram made of brass.

. I One kilogram made of brass. One gram made of brass. One set of small silver weights

, from 4 decigrams to 1 milligram.

6. International Standards of Weights and Measures

It is necessary at this point to go back a few years

md give an account of the establishment of the Inter- national Bureau of Weights and Measures, since the

^resent fundamental standards of length and mass for

'practically the whole civilized world result from the

:stablishment of that institution.

In response to an invitation of the French Government, the following countries sent representatives to

a conference held in Paris on August 8, 1870, to consider the advisability of constructing new metric

standards: Austria, Colombia, Ecuador, France, Great

Britain, Greece, Italy, Norway, Peru, Portugal,

13
Russia, Spain, Switzerland, Turkey, and the United

States of America, 15 countries in all. This confer- ence was of short duration, on account of the war

then raging between France and Germany.

A second conference was held two years later, at which 26 countries, including the United States, were

represented. At this conference it was decided that

new meters and new kilograms should be constructed

to conform with the original standards of the Archives,

and a permanent committee was appointed to carry

out this decision. The preparation of the new standards had advanced so far by 1875 that the permanent

committee appointed by the conference of 1872

requested the French Government to call a diplomatic

conference at Paris to consider whether permanent means and appliances for the final verification of the

new meters and kilograms should be provided, or whether the work should be regarded as a temporary

operation.

In compliance with this request a conference was

held in March 1875, at which 20 countries were

represented, the United States as usual being included.

On May 20, 1875, 17 of the 20 countries represented

signed a document known as the

'

' Metric Convention"

or the "Treaty of the Meter." This provided for

the establishment and maintenance of a permanent

International Bureau of Weights and Measures to be

situated near Paris and to be under the control of an

international committee elected by the General

Conference on Weights and Measures.

In addition to the original primary work of verifying the new metric standards the International Bureau

was charged with certain duties, the following being

the most important:

(1) The custody and preservation, when completed,

of the international prototypes and auxiliary instruments.

(2) The future periodic comparison of the several

national standards with the international prototypes.

(3) The comparison of metric standards with

standards of other countries.

The expenses of the bureau were to be defrayed by

contributions of the contracting governments, the

amount for each country depending upon the population and upon the extent to which the metric system

was in use in the particular country.

After ratification by the U.S. Senate and the ex- change of ratifications at Paris, the Metric Convention was "proclaimed" by Rutherford B. Hayes,

President of the United States, on September 27, 1878.

The twenty countries represented at the diplomatic

conference at which the treaty was prepared and

signed were Argentina, Austria-Hungary, Belgium,

Brazil, Denmark, France, Germany, Great Britain,,

Greece, Italy, the Netherlands, Peru, Portugal, Russia,,

Spain, Sweden-Norway, Switzerland, Turkey, the

United States of America, and Venezuela. Three of

these countries did not sign the convention at that

time—Great Britain, Greece, and the Netherlands.

Under the terms of the Convention an International

Conference of Weights and Measures was established,

to meet once every six years and to comprise official

delegates designated by each Power signatory to the

Convention. The International Committee elected by

this Conference meets every two years.

A Convention amending the 1875 Convention was

signed at Sevres, France, on October 6, 1921; after the

customary preliminaries this was proclaimed by President Calvin Coolidge on October 27, 1923. Among

othe^r amendments made, the new Convention broadened the scope of the work of the International Bureau,

enlarged the International Committee from 14 to 18

members, revised the method of calculating the con

tributions to be assessed against signatory countries

for the support of the Bureau, and modified the

procedure for access to the standards vault at the

International Bureau.

The number of powers adhering to the Metric

Convention—and thus supporting the International

Bureau—has increased to 37. Of the original 17,

Peru and Venezuela have withdrawn, and AustriaHungary and Sweden-Norway have each separated

into 2 powers. Additional adherents comprise Australia, Bulgaria, Canada, Chile, Czechoslovakia,

Dominican Republic, Finland, India, Indonesia, Ire-' land, Japan, Korea, Mexico, the Netherlands, Poland,

Rumania, Thailand, Uruguay, the United Kingdom,

and Yugoslavia.

The International Committee has had as members,

at one time or another, many of the world's leadingi

metrologists. The United States has been represented on the Committee by J. E. Hilgard (1875-1897),

B. A. Gould (1887-1896), A. A. Michelson (1897-

1905), S. W. Stratton (1905-1931), A. E. Kennelly

(1933-1939), E. C. Crittenden (1946-1954), and A. V.

Astin (1954- ). The International Bureau of Weights and Measures

is situated in the town of Sevres, France, near the

Sevres end of the Park of St. Cloud, which extends

between the towns of St. Cloud and Sevres. The

plot of ground was ceded by France to become international territory. The main office building, used

also for the library and for the home of the Director,

was originally a royal dwelling known as the Pavilion de Breteuil. The present official address of

14
The International

Bureau of Weights

and Measures,

Sevres, France.

the bureau is Pavilion de Breteuil, Sevres (Seine-etlOise), France.

The construction of the meters and kilograms had

I been entrusted to a special committee which carried

out its tasks meticulously and with great scientific

thoughtfulness. These international and national

standards were designated as "prototypes," a term

that is confusing in the minds of many people. Notwithstanding the dictionary definition of "prototype" as the original, model, or pattern after which

something is copied, the term in metrological

usage signifies that which is first in status or chief in

rank or importance, a usage that dates back at least to 1875- Thus the expression "International ProtoItype Kilogram" is used to mean the kilogram standlard that ranks highest as an international standard,

that provides the most authentic value in the world

for the kilogram mass, and not necessarily as the

pattern for the construction of other kilogram standards. The expression "United States National Prototype Kilograms No. 20 and 4" is used to mean the

particular kilogram standards, identified as "No. 20"

and "No. 4," respectively, which standards rank

highest in this country.

The international and national prototype meter

bars, constructed in accordance with the terms of the

Convention of the Meter of 1875, are of like design;

the cross section is designed to provide maximum

rigidity in a bar of reasonably small dimensions and

mass, and to reduce to a minimum the effects of any

slight bending that may take place when a bar is in

normal use. This cross section is a modified X known

as the "Tresca section" in honor of the French

scientist, Henri Tresca, who proposed it. The overall

dimensions of the cross section of the prototype meter

bars are 20 x 20 millimeters.

In a bar of Tresca cross section, the upper surface of

the central rib lies in the plane of the neutral axis of

the bar, the plane in which any variations in the

length of the bar that may be caused by slight deformation of the bar are reduced to the practicable

minimum.

The international and national prototypes are approximately 1020 millimeters in overall length.

As originally constructed (some bars have been

regraduated in recent years), near each end of a bar, on the upper surface of the central rib, is a small,

elliptical, polished area, and on this area are engraved

two groups of parallel lines, the first comprising three

transverse lines and the second two longitudinal lines.

The central lines of each of the two transverse groups

are the essential defining lines of the bar, the auxiliary

lines being positioned at one-half millimeter distances on either side. (These auxiliary lines were intended

for such purposes as calibrating the micrometer

microscopes of length comparators.) The lines of

each transverse group are crossed by the lines of a longitudinal group, these latter lines being 0.2 millimeter apart and somewhat more than 1 millimeter in

length; the longitudinal lines serve to identify that

small portion of each defining line that is to be utilized

when the bar is used. Also engraved on each bar is

its identifying number.

As for the international and national kilograms,

they are in the form of right circular cylinders of

equal diameter and height—approximately 39 millimeters-—with slightly rounded edges. Engraved on

each is its identifying number.

Thirty-one meter bars and 40 kilograms were

constructed under the supervision of the International

Bureau. The work of construction and calibration

was completed by 1889; and in September of that year

15
the first General Conference on Weights and Measures

was held in Paris, and this work was approved at

this meeting.

The meter and kilogram that agreed most closely

with the meter and kilogram of the Archives were

declared to be the international meter and the international kilogram. These two standards, with

certain other meters and kilograms, were deposited

in a subterranean vault under one of the buildings of

the International Bureau, where they are only accessible when three independent officials with different

keys are present. The other standards were distributed by lot to the various governments contributing

to the support of the International Bureau. Those

falling to the United States were meters Nos. 21 and

27 and kilograms Nos. 4 and 20.

7. The Men

On April 5, 1893, T. C. Mendenhall, then Superintendent of Weights and Measures, with the approval

of the Secretary of the Treasury, decided that the

international meter and kilogram would in the future

be regarded as the fundamental standards of length

and mass in the United States, both for metric and

customary weights and measures. This decision,

which has come to be known as the "Mendenhall

Order," was first published as Bulletin No. 26 of the

Coast and Geodetic Survey, approved for publication

April 5, 1893, under the title,

'

' Fundamental Standards

of Length and Mass" ; it was republished in 1894 under

the same title, as appendix No. 6—Report for 1893

of the Coast and Geodetic Survey, "to give it a more

permanent form." In appendix No. 6 there was

included as an addendum to the text of Bulletin No. 26

a section headed "Tables for Converting Customary

and Metric Weights and Measures," comprising

some text, five customary-to-metric conversion tables,

and five metric-to-customary conversion tables.

Meter No. 27 and kilogram No. 20 were brought"

under seal to this country by George Davidson, of thes

Coast and Geodetic Survey. On January 2, 1890, the: packing cases containing these standards were opened!

at the White House and the standards were accepted

by President Harrison, who certified that they were

received in good condition and that he confidently

believed that they were the standards referred to in; the reports. These reports, relating to the standards

in question, had been submitted by B. A. Gould, j United States delegate to the International Conference ' on Weights and Measures, and by Davidson. The

other two standards were received the following;

July and were deposited in the Office of Weights and

Measures, where those accepted as national standardsby the President had already been taken.'''

enhall Order

As a matter of interest and record, the full text of

appendix No. 6 of the Report for 1893 of the Coast

and Geodetic Survey, with the exception of an

editorial footnote and the ten conversion tables, is; reproduced as appendix 3 of this publication. i The Mendenhall Order initiated a departure froml

the previous policy of attempting to maintain our

standards of length and mass to be identical with;

those of Great Britain, and thereafter there was a small difference between the British and the United

States yards, a difference which may have been negligible in 1893 but which became of real importance as the British Imperial Yard bar gradually changed in

length and as the requirements for greater accuracy

in measurements increased.

As has been seen, when the United States yard was

first adopted upon Hassler's recommendation in 1832,

it was defined as a particular interval on the Troughton

bar, through which it was related to the British yard

standard. The intention was to fix the United States

yard as equal to the British yard.

When the "Imperial" system of weights and

measures was established by the British in 1824, the

Imperial Yard was defined in terms of a specific yard

standard and a particular bar was legalized as the

Imperial standard. In 1834, that bar was so damaged

in the burning of the Houses of Parliament that

replacement was necessary; a new bar was constructed,

and in 1855 this bar was legalized as the new Imperial

Standard Yard. In the course of the years this bar

proved to be insufficiently stable in length and was

found to be shortening by measurable amounts. —

Upon the establishment of the Buieau of Standards on July 1, 1901, all standards and other property In possession of the Office of Weights and' Measures passed under the control of the Bureau.

16
r For a time, efforts were made by United States

'authorities to maintain equivalence between the

United States and British yards. Such efforts were

'abandoned, however, in 1893, when the Mendenhall

'Order (see appendix 3, p- 26) defined the United States

lyard in terms of the International Prototype Meter.

The difference between the United States and the

British yards, prior to the 1959 actions of both govrnments in recognizing the new International Yard

Csee appendix 5, p- 28), reached a maximum value

in the order of 0.000 13 inch, the United States yard

being the longer.

i The case of the pound was slightly different as will

'be seen from the record of the values assigned to it with respect to the kilogram.

The United States law of 1866 that made the use of

the metric system permissive, carries the relation,

1 kilogram =2.2046 avoirdupois pounds, an equation

now believed to have been intended as sufficiently

accurate for commercial purposes but not as a precise

definition of the relationship between basic units.

This value resulted from a rounding off of the results

|of an 1844 comparison made in England between the

British pound and the Kilogram of the Archives

iwhich gave the relation, 1 pound =0.453 592 65 kilogram; this relation was used in Great Britain and in

the United States for years. Expressed reciprocally,

this relation becomes, approximately, 1 kilogram =

Z.204 621 61 pounds.

In the Coast and Geodetic Survey Report for 1893

that contained the Mendenhall Order, (see appendix

3, p. 26), the kilogram-avoirdupois pound relationhips are variously stated as follows:

1

2.2046

1

2.20462

kg

kg

= 1 kilogramme =453.592 427 7 grammes

I pound avoirdupois

I pound avoirdupois

L204 622 34 pounds

avoirdupois

I avoirdupois pound

A comparison made in 1883 between the British

Imperial Standard Pound and the International Pro-

:otype Kilogram resulted in the relation 1 Imperial

?ound =0.453 592 427 7 Kilogram; this relation was

iccepted in both Great Britain and the United States,

but uniformity between the two countries ended in

1889 when Great Britain officially adopted a roundedDff value, making the relation, 1 Imperial Pound =

0.453 592 43 Kilogram. From its founding in 1901

antil July 1, 1959, the National Bureau of Standards

recognized and used the relation 1 pound avoirdupois =0.453 592 427 7 kilogram.

This uncertainty as to the precise values of the

units of length and mass in common use, the yard and

the pound respectively, was caused by inadequacies

of the standards representing them. The bronze

yard No. 11, which was an exact copy of the British

imperial yard both in form and material, had shown

changes when compared with the imperial yard in

1876 and 1888 which could not reasonably be said

to be entirely due to changes in No. 11. Suspicion

as to the constancy of the length of the British standard was therefore aroused. Neither the troy pound

of the mint nor the copies of the imperial yard in the

possession of the Office of Weights and Measures were

satisfactory standards. The mint pound is made in

two pieces, the knob being screwed into the body;

hence its density can not be determined by weighing

in water on account of danger of leakage. Moreover,

it is made of brass not plated, and therefore liable to alteration by oxidation.

On the other hand, the new meters and kilograms

represented the most advanced ideas of standards, and

it therefore seemed that greater stability in our weights and measures as well as higher accuracy

would be secured by accepting the international

meter and kilogram as fundamental standards.

Time proved the wisdom of this action, and therefore when the National Bureau of Standards was

established in July 1901, it fully accepted the decision

made by the Office of Weights and Measures in 1893

to adopt the meter and kilogram as fundamental

standards.

The National Bureau of Standards was established

in response to the requests of scientists, technologists,

and industrialists that a governmental agency be

founded to develop standards, carry out researches

basic to standards, and calibrate standards and devices.

The Office of Weights and Measures had carried out

some of this^ work in its limited field, and the increasing use of electricity was making the need of a central

standardizing authority rather critical. Similar needs were also felt in other fields of science and industry.

Institutions of the type envisioned had already been

formed in Great Britain and Germany and the Office

of Weights and Measures was deemed to be a suitable

nucleus on which to build in this country. Fortunately, Congress was favorably impressed with the

idea and on March 3, 1901 it passed an act providing

that "The Office of Standard Weights and Measures

shall hereafter be known as the National Bureau of

Standards" and setting forth the functions of the new

Bureau. These functions were considerably expanded

in an amendment passed in 1950.

17
He ii kiiOM'n I'litit on lliia accoiid. day ofJanzco-ry Jl. D. one tIu}iuian£L ei^ht toLTi-dLr^ti arui ninBty

Ml llie G/joflVas/iiiiffton thereweri: eJcJtihitetJ ic/bre ine^ ^ery'^ii/iirt, Jia^iison ^ J^-e-sitiefit oftlijC X7iuitef2 Utate/s, by

TC.Jtencii'iiluill^ Sitpei-tuientieiU a/'the. MiLL/ed Malfs . CocLSt aiuL GeocZett-r Sxan'ey twM..fia£k£rt^.ij>Jif:js. d/^sMrjilifoL.as tbUonSi

One l/o^- bcai-iiuf ihcsiciLcil Tuuiib^.r 21 a.nxt -iSifalfcL twJce..jvUft^iiejii,ii/a~r l>ejifiTLif. tlie impt:eAS ot'a-iCr<s{it oyprtbe

OoUiu- iriler %.

(hif strict U huioe<1 bo.r beaiitig tJie .vtfiicil itumbfi- 20 ajt^ Oie UtterA and- Aealeei Imce witti- Te4jLliaJC iejirprpg

Ihe intpif.s.s of a crest ovtii- the OoHiir JetU.r ax before dejtci-ibe-d^ and wilhluio black seals -uttA tJie Ootbxc letters TCti.^S^,

J'linl ihv Liiifiression of'thr red iiajr sralu a/bresaid was rccoifiiLxfd <?.v t/iaJ: of Oie private seaX of2>t: JSeiij^anLi-n^

Afjthorp (joiiJd, Uuitc4i •Sttxtes Mele^cute to t/ie IiiteriiationoZ Canferejice on fVeifflUs aiid.Jifcasicres com e^rve^ out Jiuris

Sff/lcniic/- ^'/J 188!), tiiat tliere tras also cjcltilbiUd a report by soul Ji.jl. Otni/d tt} U^c ^ecre.ta/y of SUcte recitinff

ih/it he received ajid. a£ceptedy oil behalfof(Jie Vmted States a prototype Met/c iiumbered 27 tnc^e/tier txitJu a.tioth^r

onr /III nibered a^tS*^ -in-^tre bar' ofthe nZloy I'fJt)'?^ rujuiitfc-red. ^ toi/etltej' iiif7i. tit-o protyitype J^i/ot^ ra trr/rtes^ one^

numbered 4, a'^d ojic/LU-riUtered- 20 » U.h- theu- arcesaories^ &ccepli rUf t/ieJ-trtovLcters : and tliat /ic encZ^scut. .srtjUt

pToto type Metre ^o.ZT.a^nl said prototype JiUi<iptt mmr Sfu. 2() >ici/i its (iccefsor/e.v ui, tlieir inner crises ajixZ^ t/Le^se.

trv tjieii liurt ui bo.Tces TitarLiul and ULeiea/ier seo/cd ly /tini as above descri/icfZ and t/iaM saift bojice^ were cf/^ii^ereM,

by- ht.ni to Mr. W/iitetrtn Jieid^ Unilt'd States JJiii ister at J\i ris, mid there ii aji n/so e.vtiit>iiecL a, rt^ior'L b v (reor^ e TyoA^ntsonf.

jtsKista^iit DruMui >Statjts Coast a iitl O&odctic SLir\-ey, afHrituii(i t/iat ttiesc l/o.res w.erc received, ty tci/iu froiri. th/i

Vrute<i States ^ft ii ister at J'aris on. tjctober "7^'' lli8!> as /n-iiu) tJic Itiijecs srtfiposed tio corvlaJ-rvllie. 7Vatiati.aZ J^ototype.

3f<-t/-ti JVo.'^J^ ajttl the JVfjtiA'ri (I I J^iup(dsf>e Jiitoifia in nie TVo. wdJi its o-ccessoriltls

That tlie SuperiiUendent ofthje Coast and <iex>de tic Siu vey did uftirin. (tiat tJtese bocces n ere reiCewe^iL T>y

7it.in r'roni ttie said' G&ore^t: J)a-yi dsoir on ttie -'7 "' day ot'JVoi rni tie/- JtifiS at f/ie (ttiice of tice Coast miCL Gex>cljetu^

Sui-ye^ ' xit, }Vu.i/miytmu J). O. cintt ttcat tht'y Itai e rem otji^!^. m /as possessio/c, s-cciteet a Jt-d n'itji. ttieu- cx>rzt.e}it^

icrLitistiirbcCL in ever\' pa,rttciJ-lar from ilie date of tlierr cijeljvpiy atinesat cL 1 1 iitiJ thus CJCfvLlil-tcoL

Thtif tite a fo resard' boJCe^ beCiiif tji^reupon.. opened in. my presence nere tbnrod to coi it^xu the, cruoer Cetscs rzs

descriZiecL x.ii, tJie, oJiire-iiLe-iitiorLed report of J)i: Ji.jl. GouIaJ tz/ui Uiese imier ctises fieiritj opeiueCL tyere, tba^rtCL

to corrtcLLix. CL MeZre bcw niLriiiered 27 o-jui celCilocfrairLine -wer^/it lATo. 20 in, (fooj. prese.rA,'atix>it clh,c7j appccrentit

III, eyery ptcrtLciiZaj' vn, tlie stinte. state, cls 'nheii, first e nclaseci tlierccic ^ aiul ifhrcJc I tjierefore, cont'icfM^iitty

helitve tv he the vdMiLtjCcat StaiiCLurds reterred l,o in, ttie aforesa,cei reports.

u
r/^ ceremor^ ofir-eaUn^ Unseal, of

^ •

proU^typ. Metre ^0 2, ^n^ K^gra^^^^ ^^

ry 2'

1890.

Ka

testimony thereof

'aJhi^U>?i Tress.

Certificate in relation to the receipt of

the national prototype metric standards

of length and mass.

The original of this certificate is preserved

in the standards vault of the National Bureau

of Standards.

Certificate in relation to the ceremony of breaking the

seals of Meter No. 27 and Kilogram No. 20.

The original of this certificate is preserved in the standards

vault of the National Bureau of Standards. It will be observed that the last signature on this certificate that of

Louis A. Fischer, who signed as Adjuster, Office of Weights

and Measures.

19
In expanding the work in weights and measures

into a national standards bureau, the work in the field of weights and measures had more opportunities for

growth. Mr. Louis A. Fischer, Chief of the Division

of Weights and Measures from the organization of the

National Bureau of Standards in 1901 until his death

in 1921, probably was the first man in the United

States to undertake the promotion of weights and

measures supervision on a national basis. In 1902,

Mr. Fischer directed scattered inspections of weighing

and measuring devices and transactions involving

quantities in several of the larger cities in the State of

New York. The purpose of these visits was to determine what amount of protection the buying public

was receiving against short weight and short measure

in purchases. As a result of this investigation, as well as the increasing number of complaints being

received in Washington, staff" members of the National

Bureau of Standards decided in 1904 to call a meeting

of weights and measures officials and other officers of

the State governments to discuss ways and means of

affording to the public adequate supervision over weights and measures in everyday transactions.

This meeting was held in Washington in 1905, and,

although invitations went to all States, the meeting

was attended by only eleven persons, representing

eight States, the District of Columbia, and the

National Bureau of Standards. As it turned out, this

was the first National Conference on Weights and

Measures, and was the inauguration of meetings that

have been held annually with exceptions due to war or other national emergency. Interest, attendance, and

participation in the Conferences, as well as the

influence of the Conference, have increased steadily.

The registered attendance at the 47th meeting, held in

8. Refinement of Values

When the National Bureau of Standards began its work in 1901 the principal units of weights and measures in the U.S. customary system were defined as follows:

ill

Washington during June 1962, was 420. Out of th

National Conference on Weights and Measures ha

come the basis for uniformity of weights and measure law and enforcement activities.

The delegates to the first Conference and to a.. subsequent meetings have had as their principal ait ja the application of uniform and satisfactory standard

of measurement to everyday commercial transaction!)

The need for uniformity of State weights and meai

ures legislation was one of the principal reasons fc the first national meeting of weights and measure

officials and was considered at that time. As the n

suit of a resolution of the second meeting, a Mod(

State Law on Weights and Measures was composed

In the year 1911, after detailed and extensive discui

sions, the Sixth National Conference adopted, with

few minor changes and additions, a Model Law th<- had been drafted at the National Bureau of Standard

Since that time this document has been subject t continued study and revisions, additions, and d' letions have been made as needed. Thus was mac

available to the States a model upon which individu;;

State legislation could be patterned.

Supplemental to the Model Law are codes of specilj

cations, tolerances, and regulations for commerci,

weighing and measuring devices which n

especially critical attention, because many of tl States officially adopt these requirements by refereni or citation with cumulative provision, resulting : their being given legal status upon adoption by tl Conference and publication by the National Bureau

Standards. Manufacturers of equipment are guide

in their engineering designs, and essentially all weigh

and measures inspectors aline their procedure:

according to the Conference codes.

for the Yard and Pound

B

iS!

1 yard=

3600

meter

3937

1 pound = 0.453 592 427 7 kg

1 gallon 231 cubic inches

1 bushel = 2 150.42 cubic inches

These definitions remained unchanged for 58 years,

and the last two are still the official values.

The precision requirements in length measurements

increased greatly during these years, and the differ- ences between the U.S. inch and the British inch

became especially important in gage-block standardization. The difference between the U.S. pound ar the British pound was also rather annoying. As

result of many years of preliminary discussion, tl directors of the national standards laboratories

Australia, Canada, New Zealand, South Africa, tl United Kingdom, and the United States entered ini agreement, effective July 1, 1959, whereby uniformi

was established for use in the scientific and technic'

fields. The equivalents 1 yard =0.9144 meter (when

1 inch =25 -4 millimeters) and 1 avoirdupois pound0.453 592 37 kilogram (whence 1 grain =0.064 798 'j gram and 1 avoirdupois ounce = 28.349 523 125 gram' were adopted for each of these national laboratoric

It will be noted from the U.S. announcement (si appendix 5, p- 28) that these same equivalents w.i also be used in this country in trade.

20
9. Wavelength DeFinition of the Meter

It is obvious that exactness in units must have its

! SIS in standards that are as permanent and exact as

issible. Ever since 1890 when Michelson made his

imous measurements of the wavelength of light in

irms of the meter, metrologists have been giving

(insideration to the idea of defining the meter in rms of the wavelength of light. Researches by

lany scientists have been carried out to find a waveil ^th generally acceptable for use as an ultimate

landard and to specify the conditions of its use.

jnally, on October 14, I960, the 11th General Conrence on Weights and Measures adopted a new

rhnition of the meter as 1 650 763-73 wavelengths of

le orange-red radiation of krypton 86, or more

lecifically in scientific terms, as 1 650 763-73 wavengths in vacuum of the radiation corresponding to

le transition between the levels Ipio and of the

•ypton 86 atom.

- The National Bureau of Standards has adopted this

t;finition (see appendix 6, p. 30), and thus it will

\n be necessary for the United States prototype meter

Jo. 27 to be taken to the International Bureau for

')mparison as has been done in the past—in 1903,^*

911, 1956, and 1957—where its relation to the interitional prototype meter has been found to remain

-sentially constant.

i The international prototype meter will continue to

fe maintained at the International Bureau and comparison of national prototypes with it will continue

to be made. Likewise, the national prototype meters

at the National Bureau of Standards will continue to

be used for many precise calibrations of length standards.

An interesting sidelight on the change in the definition of the yard is found in measurements made just

prior to April 1893 indicating that

1 U.S. yard= 0.914 399 80 meter

or

1 meter=39.370 09 U.S. inches

a relation which differs by only 2 parts in 9 million

from the value finally adopted in 1959. The observers,

however, had in mind the value given in the 1866 law

and noted that the value 1 meter =39-3700 inches "is

evidently sufficiently precise for geodetic purposes and

has the advantage of being convenient and easily

remembered."

Although some thought has been given to a possible

definition of the kilogram in terms of some invariable

physical phenomenon instead of in terms of a material

standard, no satisfactory solution has yet been discovered. The U.S. national prototype kilogram No.

20 was compared with international standards in 1937

and 1948 with excellent results.

10. Other Definitions of Units

Three other changes in the weights and measures

:ld have occurred during the past 60 years. First,

lere was the change made in 1911 in the law defining

le troy pound. At that time the words " the standrd troy pound of the Bureau of Standards of the

^nited States" were substituted for the description

f the troy pound of the Mint.

Next, in 1913, the international metric carat was

efined as the equivalent of 200 milligrams, thereby

eliminating the use of a number of unofficial or semiofficial carats. Third, in 1954, the Secretary of Commerce and the

Secretary of Defense agreed to use the international

nautical mile in their respective departments instead

of the older U.S. nautical mile. (See appendix 4,

p. 28.) The practical effect of this action was that

the use of the U.S. nautical mile has virtually disappeared.

I. Current and Historical Standards of Length and Mass at the National Bureau

of Standards

This history of weights and measures in the United

tates concludes with a descriptive list of some of the

lore important standards of length and mass either

's In 190.3 there was an apparent shortening of appro.vimately 0.4 ^ in meter

ir No. 27, but subsequent observations showed that there had been no

ortening of this bar, but rather a lengthening of the two laboratory meter

irs used in the comparisons and small eriors in the coefficients of thermal

pansion of the bars involved.

(a) currently in use or (b) not in current use but of

historical interest, that are in the custody of the

National Bureau of Standards.

Standards Currently in Use

Meter 17. —National prototype meter, a line standard

made of platinum-iridium, Tresca cross section (modified X), received by the United States from the Inter21

Early view in the

standards vault of the

National Bureau of Standards

Formerly the national prototype standards of length and mass were kept in a cabinet at one

side of the standards vault, as here illustrated. This view shows Louis A. Fischer, first Chief of the Division of Weights and Measures of the Bureau and, as such, custodian of the national prototype meter and kilogram.

Imperial

avoirdupois

pound,

copy No. 5.

Front and top views

23
national Bureau of Weights and Measures in 1889.

This meter was the United States national reference

standard for all length measurements from 1893 to I960, and in I960 became the primary bar, secondary

only to the basic value of the meter in terms of the

wavelength of Kr*'' light.

Meter 21. —National prototype meter of same material and design as Meter 27, received by the United

States from the International Bureau of Weights and

Measures in 1890.

Meter 12. —A platinum-iridium line-standard meter,

Tresca cross section (modified X), made of the "Alloy

of 1874," and received by the United States from the

International Bureau of Weights and Measures in 1889.

It was regraduated in 1948 by the National Bureau of

Standards in terms of the wavelength of red cadmium

light.

Meter 4. —A platinum-iridium graduated line-standard meter, Tresca cross section (modified X), made of

the "Alloy of 1874," and purchased by the United

States in 1907. It is graduated to 1-millimeter divisions for the entire 1-meter interval and is of special

utility in making comparisons of intervals of less than

1 meter.

Kilogram 20. —National prototype kilogram, a mass

standard made of platinum-iridium in the form of a cylinder of equal diameter and height, received by

the United States from the International Bureau of

Weights and Measures in 1889- It has been the

United States national reference standard for all mass

measurements since 1893.

Kilogram 4. —National prototype kilogram of same

material and design as Kilogram 20, received by the

United States from the International Bureau of

Weights and Measures in 1890. It is secondary to Kilogram 20.

Standards of Historical Interest

Cotmmttee Meter. —An iron end standard of length, 9

millimeters by 29 millimeters in cross section. This

bar is one of a group of similar bars made in France in

1799 by the committee that made the Meter of the

Archives, whence its designation in the United States

as the "Committee Meter." This particular bar was

presented by Tralles, the Swiss member of the committee, to his friend F. R. Hassler; Hassler, in turn

sold it to a member of the American Philosophical

Society in Philadelphia, who deposited it with the

Society. Later the bar was obtained from the Society

by Hassler for the use of the U.S. Coast and Geodetic

Survey, where it was used as the standard for scientific

work in the United States from 1807 to 1893.

Arago Meter. —A platinum line standard of length, 5 millimeters by 25 millimeters in cross section. The

bar was procured from France in 1821 by Albert Gallatin, Minister of the United States to France, it derives

its designation from the name of the eminent French

physicist who certified the length of its graduatec,

interval. It appears that this bar has receivec

essentially no use as a standard in the United States

Troiighton Scale. —A graduated line standard o); length, commonly designated as an 82-inch bar, made

by Troughton of London in 1814 and procured in 181!

for the United States by F. R. Hassler. The bar, >' inch by 2)^ inches in cross section, is made of bras: with an inlaid silver strip on which ){o-mch gradui

ations are engraved. The interval between the 27tl! and 63d inch graduations was selected by Hassler it 1832 to define the United States standard yard, and tht Troughton Scale retained its position as the priman

reference yard standard of the United States unti

about 1857.

Bronze Yard No. 11. —A bronze line standard o: length, 1 inch by 1 inch in cross section, having ai overall length of 38 inches. Near each end of thi bar is a cylindrical well with an inset gold plug, thi; upper surface of the plug being ^2 inch below the toj

surface of the bar. The 1-yard defining lines ar engraved on the gold plugs. This bar is of the sam

material and form as the British Imperial Yard legal

ized in 1855, and was presented to the United State

by Great Britain in 1856. It was used as the standar

yard of the United States from about 1857 to 1893-

Low Moor Iron Yard No. 57. —An iron line standar

of length, similar in design and construction to Bronz

Yard No. 11. It was presented to the United State; by Great Britain in 1856, and was in use in the Unite

States as a standard until 1893, being regarded a secondary in importance to Bronze Yard No. 11.

Committee Kilogram.—A brass standard of mass

cylindrical, with knob. This standard is one of

group of similar standards made in France in 1799 b

the committee that made the Kilogram of the At

chives, whence its designation in the United State

as the "Committee Kilogram." This standard wsj

presented by Tralles, the Swiss member of the cou;

mittee, to his friend F. R. Hassler, Hassler, in turr' sold it to a member of the American Philosophies!

Society in Philadelphia, who deposited it wit,

the Society. Later, the standard was obtainci

from the Society by Hassler, who made use of it ii connection with his standards work for the U.Si

Coast and Geodetic Survey.

Arago Kilogram.—A platinum kilogram made i'lSjji France by Fortin and certified by Arago. It was pre |!itf|

24
cured in France in 1821 for the United States by

Albert Gallatin, Minister of the United States to

France. Prior to 1890, this kilogram was used as one of the standards of the United States.

i- Silbermann Kilogram.—A gilded brass standard of

!mass, cylindrical, with knob. This standard was

presented to the United States by France in 1852,

jand became a secondary standard in the Office of

[Standard Weights and Measures of the U.S. Coast

and Geodetic Survey, used particularly in connection

with the adjustment and verification of metric standards supplied to the States.

Grave.—A cylindrical knob weight, one of six made

in 1793 by the French Temporary Commission on

Weights and Measures as representing the unit of

weight of a proposed system of weights and measures.

Originally called the "grave", in 1795 the unit was

L-enamed the "kilogram." This weight is from a set

of weights brought to the United States in 1793, and

it appears that the set came into the possession of one Andrew Ellicott, at one time an assistant to Major

Pierre Charles L'Enfant who planned the city of Washington. The subsequent history of this set of weights

Appendix 1.

j The first of the following principal sources consulted

in the preparation of this publication was used very

extensively. It is therefore placed at the head of the

'list; the others are listed alphabetically.

TFISCHER, Louis A., History of the Standard Weights

' and Measures of the United States, NBS Miscellaneous Publication 64;

iBACHE, Alexander D., Report on the Construction

' and Distribution of Weights and Measures, S. Ex.

, Doc. No. 27, 34th Congress, 3d Session;

BIGOURDAN, Guillaume, Le Systeme Metrique des

Poids et Mesures;

|CHANEY, Henry J., Our Weights and Measures;

is somewhat obscure, but it seems probable that the

set remained in priv^ate hands, probably within the

Ellicott family, until 1952, when what remained of the

set was donated to the National Bureau of Standards

by its owner at that time. Dr. A. Ellicott Douglass of

the University of Arizona.

"Star" Avoirdupois Found.—A cylindrical knob

weight marked on the top surface of the knob with a

star. Although positive identification cannot be

made, it appears not unreasonable to assume that this

standard is the actual weight "made by Mr. Hassler

from the troy pound in the United States mint, and

marked with a star (commonly designated as the star pound)," as referred to by A. D. Bache, Superintendent of Weights and Measures, in his report of

December 30, 1856, to the Secretary of the Treasury.

Imperial Avoirdupois Pound, Copy No. 5. —-A goldplated brass standard of mass, cylindrical in form

with a circumferential groove (instead of a knob) to

facilitate handling. This standard was received in

1856 as a gift from Great Britain to the United States.

It was used as the standard representing the United

States avoirdupois pound from 1856 to 1893-

Bibliosraphy

CHISHOLM, Henry W., On the Science of Weighing

and Measuring and Standards of Measure and

Weight;

GUILLAUME, Charles E., La Creation du Bureau

International des Poids et Mesures et son Oeuvre;

HASSLER, Ferdinand R., Comparison of Weights and

Measures, H. R. Doc. 299, 22d Congress, 1st Session;

BOARD OF TRADE, GREAT BRITAIN, Reports on

their Proceedings and Business under the Weights

and Measures Act 1878;

COMITE INTERNATIONAL DES POIDS ET MESURES, Proces Verbaux des Seances;

CONFERENCES GENERALES DES POIDS ET

MESURES, Comptes Rendus des Seances.

Appendix 2. Report on the Troy Pound of the Mint

t Reproduced below is the text of an appendix to the

report of the Committee of the Franklin Institute on

Weights and Measures comprising a report of Dr.

iSamuel Moore, Director of the United States Mint,

dated October 1, 1833, dealing with the original troy

pound of the Mint. This report was printed in the

Journal of the Franklin Institute of the State of

Pennsylvania in the issue of May 1834 (Vol. XIII,

New Series, No. 5), p. 302-3.

25
APPKNDIX TO THE REPORT OF THE COMMITTEE OF THE

FRANKLIN INSTITUTE ON WEIGHTS AND MEASURES

Report of Dr. Samuel Moore on the authentication of the Troy Pound itt

possession of the Mint of the United States To the committee of the Franklin Institute charged with the subject of Weights and Measures Mint of the United States, October 1, 1833. The standard troy pound of the mint is a copy, executed with great

care, of the British parliamentary troy pound of 1758, recognised

and designated in the year 1824 as the imperial troy pound of Great

Britain. It was procured at my request, in 1827, through the atten- tion and influence of Mr. Gallatin, Minister of the United States at London. By the friendly offices of Mr. Davies Gilbert, Vice Presi- dent of the Royal Society, the standard troy pound in the care of the Clerk of the House of Commons, was, on the application of Mr.

Gallatin to the Speaker of the House, committed to the charge of Capt. Kater, for the purpose of effecting at his own house an adjustment of the copy to the original.

The standard weight is of brass, the original being of that material. It was made by Mr. Bate, who had constructed all the standard British weights, and the comparison with the original was made

by a very delicate beam constructed by Robinson, the same artist who had constructed the beam with which Capt. Kater compared

the standard weights above mentioned with the original standard

troy pound.

The weight was enclosed in a neat casket carefully enveloped

under seal of the American legation at London, and committed by Mr. Gallatin himself to the hands of Mr. Cucheval, a public messenger, bearing despatches from the legation to the United States, by whom it was delivered into my hands, accompanied by a packet

containing ample certificates from Capt. Kater and Mr. Gallatin,

testifying to the accuracy of the weight in question.

The casket and accompanying package were retained under seal, waiting the return of Mr. Adams, President of the U.S., from his family residence to Washington, in order that the seal of Mr. Gallatin, and the various facts of chief moment, in regard to the authentication of the weight, might be verified, on his authority. They

were accordingly opened in the presence of Mr. Adams, in Philadelphia, on the 12th of October, 1827, and his full certificate in regard

to the seal, which he readily recognised, and to the circumstances

generally, giving assurance of the fidelity of the whole transaction,

and the consequent accuracy of the weight, has been added to the vouchers in the case; he declaring, in conclusion, his entire belief, that the brass weight then exhibited was the identical copy of the imperial standard troy pound of Great Britain, intended and referred to in the aforesaid certificates. The above facts having been communicated to Congress through

the committee on the mint, the troy pound thus certified was specifically declared by law to be "the standard troy pound of the mint

of the United States, according to which the coinage thereof shall be regulated." See section 2nd of the act of May 19, 1827, respecting the mint, a copy of which is hereto annexed. This is the specific pound weight, assumed as the standard unit of

the system of weights reported to the Senate of the United States, under a resolution of that body of 29th May, 1830—see a communication from Mr. Ingham, Secretary of the Treasury, made to the Senate March 3d, 1831; also the report of Mr. Hassler on the subject, 27th January, 1832, pages 10 and 25; and a communication to the Senate from Mr. M'Lane, Secretary of the Treasury, accompanying

this report, dated 20th June, 1832. It has been constantly in my

possession, and is preserved with the utmost care. Very respectfully, gentlemen.

Your obedient servant, Samuel Moore,

Director United States Mint.

26

Appendix 3. The Mendenhall Order of!

April 5, 1893

This order was published as appendix 6 of the

Report for 1893 of the Coast and Geodetic Survey.

FUNDAMENTAL STANDARDS OF LENGTH AND MASS

While the Constitution of the United States authorizes Congresli to "fix the standard of weights and measures," this power has neve:: been definitely exercised, and but little legislation has been enactei: upon the subject. Washington regarded the matter of sufficient im

portance to justify a special reference to it in his first annual message

to Congress (January, 1790), and Jefferson, while Secretary of Stato

prepared a report, at the request of the House of Representatives;

in which he proposed (July, 1790) "to reduce every branch to th( decimal ratio already established for coins, and thus bring the cali culation of the principal affairs of life within the arithmetic of even man who can multiply and divide

. '

' The consideration of the subjec

being again urged by Washington, a committee of Congress reports

in favor of Jefferson's plan, but no legislation followed. In the mean'

time the executive branch of the Government found it necessary t^ procure standards for use in the collection of revenue and other oper

ations in which weights and measures were required, and the Trough

ton 82-inch brass scale was obtained for the Coast and Geodeti

Survey in 1814, a platinum kilogramme and metre, by Gallatin, i 1821, and a troy pound from London in 1827, also by Gallatin. I 1828 the latter was, by act of Congress, made the standard of mass fc the Mint of the United States, and, although totally unfit for sue purpose, it has since remained the standard for coinage purposes.

In 1830 the Secretary of the Treasury was directed to cause a corr parison to be made of the standards of weight and measure used a the principal custom-houses, as a result of which large discrepancie. were disclosed in the weights and measures in use. The Treasur Department, being obliged to execute the constitutional provisio that all duties, imposts, and excises shall be uniform throughout th United States, adopted the Troughton scale as the standard of length

the avoirdupois pound, to be derived from the troy pound of th Mint, as the unit of mass. At the same time the Department adopte I the wine gallon of 231 cubic inches for liquid measure and the Wit

Chester bushel of 2150.42 cubic inches for dry measure. In 1836 th! Secretary of the Treasury was authorized to cause a complete set c'

all weights and measures adopted as standards by the Department fc' the use of custom-houses and for other purposes to be delivered to th governor of each State in the Union for the use of the States, respec tively, the object being to encourage uniformity of weights an measures throughout the Union. At this time several States ha

adopted standards differing from those used in the Treasury Depan

ment, but after a time these were rejected, and finally nearly all th! -

States formally adopted, by act of legislature, the standards whic

had been put in their hands by the National Government. Thus . \ good degree of uniformity was secured, although Congress had nc I adopted a standard of mass or of length, other than for coinag

purposes, as already described. The next and in many respects the most important legislation upo, the subject was the act of July 28, 1866, making the use of the metri system lawful throughout the United States and defining the weight

and measures in common use in terms of the units of this system. Th: was the first general legislation upon the subject, and the metric sy; tem was thus the first, and thus far the only, system made general!

legal throughout the country.

In 1875 an international metric convention was agreed upon b seventeen Governments, including the United States, at which it ws; undertaken to establish and maintain at common expense a perm::
nt international bureau of weights and measures, the first object

which should be the preparation of a new international standard

ere and a new international standard kilogramme, copies of which

ould be made for distribution among the contributing Govern-

;:nts. Since the organization of the Bureau, the United States has

i;ularlv contributed to its support, and in 1889 the copies of the iw international prototypes were ready for distribution. This was

lected bv lot, and the United States received metres Nos. 21 and 27

:d kilogrammes Nos. 4 and 20. The metres and kilogrammes are

ide from the same material, which is an alloy of platinum with 10

jr cent of iridium. pn January 2, 1890, the seals which had been placed on metre No.

and kilogramme No. 20 at the International Bureau of Weights

id Measures, near Paris, were broken in the Cabinet room of the

lecutive Mansion by the President of the United States in the prescce of the Secretary of State and the Secretary of the Treasury,

iJcther with a number of invited guests. They were thus adopted

. the national prototype metre and kilogramme.

The Troughton scale, which in the early part of the century had

l:n tentatively adopted as a standard of length, has long been

: ognized as quite unsuitable for such use, owing to its faulty conuction and the inferiority of its graduation. For many years, in

ndardizing length measures, recourse to copies of the imperial

jrd.of Great Britain had been necessary, and to the copies of the

'i:tre of the archives in the office of weights and measures. The

:|.ndard of mass originally selected was likewise unfit for use for

iiiilar reasons, and had been practically ignored,

jrhe recent receipt of the very accurate copies of the International

i;tric Standards, which are constructed in accord with the most

|vanced conceptions of modern metrology, enables comparisons to made directly with those standards, as the equations of the

.tional prototypes are accurately known. It has seemed, there-

.e, that greater stability in weights and measures, as well as much

jher accuracy in their comparison, can be secured by accepting

p international prototypes as the fundamental standards of length i mass. It was doubtless the intention of Congress that this ould be done when the international metric convention was

tered into in 1875; otherwise there would be nothing gained from

: annual contributions to its support which the Government has

istantly made. Such action will also have the great advantage

putting us in direct relation in our weights and measures with

civilized nations, most of which have adopted the metric system

• exclusive use. The practical effect upon our customary weights

i measures is, of course, nothing. The most careful study of the

ation of the yard and the metre has failed thus far to show that

: relation as defined by Congress in the act of 1866 is in error,

e pound as there defined, in its relation to the kilogramme, differs

•m the imperial pound of Great Britain by not more than one

:t in one hundred thousand, an error, if it be so called, which

erly vanishes in comparison with the allowances in all ordinary

nsactions. Only the most refined scientific research will demand

loser approximation, and in scientific work the kilogramme itself low universally used, both in this country and in England.*

Note.—Reference to the act of 1866 results in the establishment of the

owing:

Equations.

3600

1 yard =—metre.

3937

1 pound avoirdupois = - -kg.

2 • 2046

.more precise value of the English pound avoirdupois is

1 leg., differ- 2 20462 from the above by about one part inone hundred thousand, but theequa1 established by law is sufficiently accurate for all ordinary conversions.

lS already stated, in work of high precision the kilogramme is now all but

versally used and no conversion is required.

In view of these facts, and the absence of any material normal

standards of customary weights and measures, the Office of Weights

and Measures, with the approval of the Secretary of the Treasury,

will in the future regard the International Prototype Metre and

Kilogramme as fundamental standards, and the customary units—

the yard and the pound—will be derived therefrom in accordance with the Act of July 28, 1866. Indeed, this course has been practically forced upon this Office for several years, but it is considered

desirable to make this formal announcement for the information of

all interested in the science of metrology or in measurements of

precision.

T. C. Mendenhall,

Superintendent of Standard Weights and Measures. Approved

J. G. Carlisle,

Secretary of the Treasury. April 5, 1893.

[United States Coast and Geodetic Survey.—Office of Standard Weights and Measures—T. C. Mendenhall, Superintendent.]

TABLES FOR CONVERTING CUSTOMARY AND METRIC

WEIGHTS AND MEASURES.

Office of Standard Weights and Measures,

Washington, D.C., March 21, 1894.

The yard in use in the United States is equal to |I4t of the metre. The troy pound of the mint is the United States standard weight

for coinage. It is of brass of unknown density, and therefore not

suitable for a standard of mass. It was derived from the British standard troy pound of 1758 by direct comparison. The British avoirdupois pound was also derived from the latter and contains

7,000 grains troy. The grain troy is therefore the same as the grain

avoirdupois, and the pound avoirdupois in use in the United States

is equal to the British pound.

2-20462234 pounds avoirdupois = 1 kilogramme.

In Great Britain the legal metric equivalent of the imperial gallon

is 4-54346 litres, and of the imperial bushel 36-3477 litres. The length of a nautical mile, as given below, is that adopted by

the United States Coast Survey many years ago, and defined as the length of a minute of arc of a great circle of a sphere whose surface

is equal to the surface of the earth (the Clarke spheroid of 1866).

1 foot =

1 fathom =

1 Gunter's chain =

1 square statute mile =

1 nautical mile =

1 avoirdupois pound =

15432-35639 grains =

0- 304801 metre, 9-4840158 log.

1- 829 metres. 20-1168 metres. 259-000 hectares. 1853-25 metres. 453-5924277 grammes.

1 kilogramme.

By the concurrent action of the principal Governments of the world, an International Bureau of Weights and Measures has been

established near Paris. Under the direction of the International Committee, two ingots were cast of pure platinum-iridium in the proportion of 9 parts of the former to 1 of the latter metal. From

one of these a certain number of kilogrammes were prepared; from

the other a definite number of metre bars. These standards of weight and length were intercompared without preference, and

certain ones were selected as international prototype standards. The

others were distributed by lot, in September, 1889, to the different 27
Governments, and are called national prototype standards. Those

apportioned to the United States were received in 1890 and are in the keeping of this office. The metric system was legalized in the United States in 1866. The International Standard Metre is derived from the Metre des Archives, and its length is defined by the distance between two lines

at 0° centigrade on a platinum-iridium bar deposited at the Inter- national Bureau of Weights and Measures. The International Standard Kilogramme is a mass of platinumiridium deposited at the same place, and its weight in vacuo is the same as that of the Kilogramme des Archives.

The litre is equal to a cubic decimetre, and it is measured by the quantity of distilled water which, at its maximum density, will counterpoise the standard kilogramme in a vacuum, the volume of such a quantity of water being, as nearly as has been ascertained,

equal to a cubic decimetre.

Appendix 4. The International Nautical

Mile

The following announcement is quoted from the

National Bureau of Standards Technical News Bulletin of August 1954.

Adoption of International Nautical Mile

Beginning on July 1, 1954, the National Bureau of Standards will use the International Nautical Mile in lieu of the U.S. Nautical Mile.

This decision, replacing the U.S. Nautical Mile of 1,853.248 meters

(6,080.20 feet) by the International Nautical Mile of 1,852 meters

(6,076.10333 . . . feet), confirms an official agreement between the Secretary of Commerce and the Secretary of Defense to use the In- ternational Nautical Mile within their respective departments.

The use of a mile derived from the length of a degree of the earth's meridian is very old. It is believed that the Chaldean astronomers determined the length of such a unit. Miles of this sort have been

variously called meridian miles, geographical miles, sea miles, and

nautical miles, and they have differed greatly in magnitude, some

of the values providing 10, 12, 15, and 60 miles to a degree. The

British and the U.S. nautical miles were each derived by taking 60

nautical miles per degree, but the values adopted were not the same. The nautical mile adopted by the British Admiralty equals 6,080

British feet, while the U.S. nautical mile has had the adopted value

of 1,853.248 meters, from which the equivalent 6,080.20 U.S. feet has been derived. The British foot is shorter than the U.S. foot by 1 part in 400,000, an amount which is of no importance in the ordinary transactions of everyday life but which is very important

in precise measurements.

In 1929 the International Hydrographic Bureau obtained an agree- ment from a large number of countries to adopt a value of 1,852 meters for the nautical mile, the unit thus defined to be called the International Nautical Mile. However, at the same time Great

Britain, the U.S.S.R., and the United States did not accept this value, each country preferring to retain the nautical mile to which

it had been accustomed.

Finally, in 1953 an informal group from the Department of Defense and the Department of Commence considered a proposal for inter- national standardization of abbreviations for the knot and the mile. At this meeting the general situation regarding the nautical mile was discussed, and the belief was expressed that a change from

1,853.248 meters to 1,852 meters would not affect nautical charts, the calibration of navigational instruments, or navigation. Because

there seemed to be no sound reason why the International Nautical

Mile should not be adopted in this country, the Departments i Commerce and Defense agreed to accept this value as of July 1, igs-. the announcement to be made by the National Bureau of StandardI

Identical directives, in the names of the two departments, ha\ been mutually adopted. The Department of Commerce directi\

is as follows:

Adaption of International Nautical Mile

I. Purpose To adopt the International Nautical Mile for use as a standi:

value within the Department of Commerce.

II. Implementation

After the effective date of this directive, the International Nautic,

Mile 0,852 meters, 6,076.10333 . . . feet'), shall be used with. the Department of Comtmrce as the standard length of the nautic

^ mile

Effective date This directive is effective 1 July 1954.

It will be noted that in the forgoing announcemea

one of the equivalents of the international nautica

mile IS stated as 6,076.10333 . . . feet. The thre

dots following the last digit indicate a continuim

repetition of the digit 3. By reference to appendix 5, it will be found tha

the equivalent of the international nautical mile ii feet is stated as approximately 6,076.11549 internz'

tional feet; this latest value represents no change ii the length of the nautical mile—1852 meters—bo

is merely a restatement of the equivalent in terms c the international foot which is shorter than the foi mer United States foot by two parts in a million.

Appendix 5. The United States Yar

and Pound

^ The following statement of the Department ( Commerce concerning a refinement of values for tt yard and the avoirdupois pound, approved June 2'

1959, is quoted from the Federal Register of July .'

1959:

Refinement of Values for the Yard and the Pounc

Background. The National Bureau of Standards, founded in 19C

is authorized by statute (U.S. Code, Title 15, Ch. 7, sec. 272)

undertake "The custody, maintenance, and development of t national standards of measurement and the provision of means a methods for making measurements consistent with these standarc /

* * *" Under this authority the National Bureau of Standa; has sought to refine and extend the standards to meet the continui

requirements of science and industry for increased accuracy and ui formity of measurement.

Since 1893 the National Bureau of Standards and its predecess agency, the Office of Standard Weights and Measures of the Treasu : Department, have derived the yard and the pound and the multip,^

and submultiples of these units from metric standards, namely t international meter and the international kilogram. The origir announcement of this derivation, together with the numerical rati upon which the derivations were based, is given in Bulletin ^ "Fundamental Standards of Length and Mass", of the U.S. Co;

28
id Geodetic Survey, approved for publication April 5, 1893, by the

rcretarv of the Treasury. An amendment to the 1893 Bulletin was

,ade in 1894 in which there was a small adjustment in the poundilogram ratio to bring it into closer agreement with the British

nperial pound.

In the latter half of the period since 1893 minor but troublesome

.screpancies have developed among various groups, both in this

luntry and abroad, that are concerned with very accurate measure-

'ents involving yard and pound units or their customary multiples

id submultiples. As a result of study and negotiation, it has de-

•loped that most of the discrepancies can be resolved and a high

;gree of measurement uniformity obtained by small refinements of

lie ratios defined in the 1893-94 bulletins relating the yard and pound

|i the meter and kilogram. Accordingly, the following announceient is made:

'.Announcement. Effective July 1, 1959, all calibrations in the U.S.

jistomary system of weights and measures carried out by the

iational Bureau of Standards will continue to be based upon metric easurement standards and except those for the U.S. Coast and

codetic Survey as noted below, will be made in terms of the follow-

;g exact equivalents and appropriate multiples and submultiples:

1 yard =0.914 4 meter

1 pound (avoirdupois) =0.453 592 37 kilogram

'Currently, the units defined by these same equivalents, which have

en designated as the International Yard and the International

)und, respectively, will be used by the National Standards Labora-

;ries of Australia, Canada, New Zealand, South Africa, and United

ingdom; thus there will be brought about international accord on

e yard and pound by the English-speaking nations of the world, in

'ecise measurements involving these basic units. 'Any data expressed in feet derived from and published as a result

geodetic surveys within the United States will continue to bear

e following relationship as defined in 1893:

1200

1 foot = meter

3937

le foot unit defined by this equation shall be referred to as the U.S'

jxvey Foot and it shall continue to be used, for the purpose given

)rein, until such a time as it becomes desirable and expedient to

adjust the basic geodetic survey networks in the United States, after hich the ratio of a yard, equal to 0.914 4 meter shall apply.

Relation to Previously Defined Standards

In 1866 (U.S. Code 1952 Ed., Titles 15, Ch. 6, sees. 204 and 205)

e Congress legalized the use of the metric system within the United

,ates. The law also established approximate equivalents between

stomary and metric measures. The above ratios between the yard

d pound and metric measures as well as those defined in the 1893-94

lletins are consistent with the ratios established by Congress in 66 within the limits of accuracy by which the latter are expressed.

Yanl. In the 1893 Bulletin the yard was defined as

, 3600

1 yard =—meter

aich results in the approximate relation

1 yard= 0.914 401 83 meter

ms the new value for the yard is smaller by 2 parts in one million an the 1893 yard. Numerical measures expressed in terms of the

'w unit will, therefore, be increased by 2 parts in one million.

^ Pound. The pound was defined in the 1893 Bulletin as:

1 pound (avoirdupois)=——

^—- kilogram

The 1894 amendment based on a recent determination of the British Imperial pound, gave the ratio as:

1 pound (avoirdupois)=

^ 20462234

which results in the approximate relation:

1 pound (avoirdupois)=0.453 592 4277 kilogram

Thus the new value for the pound is smaller by about 1 part in 10 million than the 1894 pound. Numerical measures expressed in terms of the new unit will, therefore, be increased by about 1 part in 10 million. Changes concern science and precision tools. Such small changes are beyond the limits of accuracy by which many reference standards

are now calibrated by the National Bureau of Standards, including

the standards furnished to or calibrated for the State governments.

Therefore, the refinements in the definitions of the yard and the pound will have no effect at all upon ordinary trade and commerce. The differences are significant, however, in a number of very precise

metrological determinations such as are found in the precision machine tool and instrument industries and in certain scientific activities. Standard inch. The value for the inch, derived from the value for the yard effective July 1, 1959, is exactly equivalent to 25.4 milli- meters. It may be noted that this value was approved by the American Standards Association for "Inch-millimeter Conversion

for Industrial Use" in 1933 (ASA Standard B48. 1-1933), was adopted

by the National Advisory Committee for Aeronautics in 1952, and

has been adopted by many standardizing organizations in other

countries.

delation to grain. The new conversion factor for the pound is exactly divisable by 7 and results in the following exact value for

the grain:

1 grain = 0.064 798 91 gram

The grain is the common unit of the avoirdupois, apothecary, and

troy systems, there being 7000 grains in the avoirdupois pound and

5760 grains in the apothecary pound and in the troy pound.

Nautical mile. On July 1, 1954, it was announced that the Secre- tary of Commerce and the Secretary of Defense had agreed officially that the International Nautical Mile would henceforth be used within their respective departments. The International Nautical

Mile is based on the meter and is equal to 1852 meters. Based on

the yard-meter relationship then in use, the International Nautical

Mile was shown as being equivalent to 6,076.10333 feet. Under the new conversion factor, the International Nautical

Mile is equivalent to 6,076.11549 International feet approximately.

(For a detailed treatment of the Federal basis for weights and

measures, see National Bureau of Standards Circular 593, The Federal

Basis for Weights and Measures, for sale by the Superintendent of Documents, U.S. Government Printing Office, Washington 25, D.C.,

price 30 cents.)

[seal] a. V. Astin,

Director, National Bureau of Standards. H. Arnold Karo,

Kear Admiral,

Director, Coast and Geodetic Survey.

Approved : June 25, 1959.

F. H. Mueller,

Under Secretary of Commerce.

[F.R. Doc. 59-5442; Filed, June 30, 1959; 8:45 a.m.]

29
Appendix 6. Adoption of the Wavelength Definition of the Meter

The following account concerning the adoption of

the wavelength definition of the meter is quoted from

the National Bureau of Standards Technical News

Bulletin of December I960:

Wavelength of Kr*° Light Becomes New International

Standard oF Length

On October 14, I960 the world adopted a new international stand- ard of length—a wavelength of light—replacing the metei bar which

had served as the standard for over 70 years. The action was taken by the 11th General Conference on Weights and Measures, which

met in Paris. Dr. Allen V. Astin, NBS Director, headed the American delegation

to the Conference. The delegation also included Louis Polk, Presi- dent, Sheffield Corporation; Elmer Hutchisson, Director, American

Institute of Physics; A. G. McNish, Chief, Metrology Division,

NBS; T. H. Osgood, U.S. Scientific Attache, London, and Marten Van Heuven and Benjamin Bock, U.S. State Department.

Other actions taken by the Conference included the establishment

of a central facility at the Internarional Bureau of Weights and Measures for international coordination of radiation measurements, confirmation of a new definition of the second of time, and adoption of refinements in the scales for temperature measurements. The new definition of the meter as 1,650,763.73 wavelengths of the orange-red line of krypton 86 will replace the platinum-iridium meter bar which has been kept at Paris as an international standard

for length since 1889 under the Treaty of the Meter. These actions of the General Conference are of great importance

to those engaged in precision measurements in science and industry. For many years the world has relied on a material standard of length—the distance between two engraved lines on the International Meter Bar kept at Paris Duplicates of the International Standard were maintained in the standards laboratories of other countries of the world. From time to time it was necessary to return these duplicates to Paris for recalibratien, and occasionally discrepant

results were obtained in these recalibrations. Also, there was doubt

in the minds of some scientists regarding the stability of the Inter- national Meter Bar. The new definition of the meter relates it to a constant of nature, the wavelength of a specified kind of light, which

is believed to be immutable and can be reproduced with great acc. racy in any well-equipped laboratory. Thus it is no longer necessa. to return the national standards of length to Paris at periodic inte vals in order to keep length measurements on a uniform hzs'' throughout the world. Also it is possible to measure some dime'

sions more accurately in terms of the new definition than was possib

before. The meter bars which have served as standards of leng ; throughout the world for over 70 years will not be discarded placed in museums because of this decision, the Conference sail They will remain important because of the ease with which th - can be used for certain types of measurement and for comparis. measurements between national laboratories. This new definition of the meter will not materially change ti measurement of length nor in any way the relation between ti; English and Metric units. Careful experiments performed at ti National Bureau of Standards by the team of A. G. Strang, K.

Nefflen, J. B. Saunders, B. L. Page, and D. B. Spangenberg immei

ately prior to the meeting of the Conference confirmed that ti wavelength standard and the metal standard are in satisfactc agreement. The inch now becomes equal to 41,929.399 wavelengij

of the krypton light

Similar measurements performed by the National Research Coun

in Canada, by Dr. K. M. Baird and his associates, are in substant agreement with the National Bureau of Standards results, adoption of the new definition, the standard of length which I been used by spectroscopists for the past 50 years is brought it! agreement with that used in other branches of science, thus incre: ing the unification of systems of measurement throughout i

scientific world. '

The orange-red wavelength is precisely described

'

the wavelength in vacuum of the radiation correspon

ing to the transition between the levels Ipio and 5di ' the atom of krypton 86.

The author acknowledges with gratitude the assj,

tance he has received in the earlier stages of t] preparation of this publication from Ralph W. Smit

himself an ardent worker for uniform weights a; measures in the United States, and in all stages frc Malcolm W. Jensen, who is now so actively engag

in that field.

30

U.S. GOVERNMENT PRINTING OFFICE; 1963 O—696760
ARAOO PLATINUM METER

FRANCE PURCHASE

The standards vault of the

National Bureau of Standards.

The prototype kilogram and

meter are made of an alloy

of 90 percent platinum and

10 percent iridium. These

and other standards are kept

in a vault, but are on daily dis- play through a heavy alarmprotected glass door. The

bottom illustration pictures

the visitors' view of the standards vault, looking through

the glass door.