Measures for Progress: A History of the National Bureau of Standards

ACQUIRING NATIONAL STANDARDS 77
reference standard a hundred-thousandth of an indh, and its primary stand-
ard a millionth of an inch.50 A time would come when industry would have
need for that millionth of an inch, and science for the ten-millionth. Con-
tinual research looking toward more precise standards, instruments, and tech-
niques was to narrow the gap everywhere in the hierarchy of standards.
Apart from length and mass and certain electrical units, few standards
were inherited by the Bureau from the old Office of Weights and Measures.
The major part of the Bureau's activities in its early years was thus spent in
establishing the discipline of standards for this country, such as other nations
already possessed, and obtaining or making the measuring apparatus and
instruments to carry out the calibrations required by science and industry.
Besides new measurements of length and mass, there was need for new stand-
ards of electrical quantities, standards of heat and temperature, of light and
radiant energy, density and pressure, and even new values for the factor of
gravity. Only the most immediate of these had been accomplished by 1904.
Not all of them were wholly satisfactory as yet but an impressive beginning
had been made.
In the weights and measures section (see above), soon to become an
independent division, as were the heat, optical, and engineering groups, the
Bureau had the two platinum-iridium copies of the international meter bar,
to which all length measurements, both customary and metric, were reduced.
Fischer had taken one of the platinum-iridium bars to Paris the previous
year and with new apparatus acquired there recompared it with that at the
International Bureau of Weights and Measures at Sèvres and found it
satisfactory.
The Bureau was now prepared to determine any standard of length
from 1 decimeter to 50 meters, to calibrate the subdivisions of such stand-
ards, and to determine their coefficients of expansion, that is, the slight
changes in dimensions when in use at ordinary ranges of temperature. Work-
ing standards derived from the Bureau's two platinum-iridium copies of the
international kilogram made it possible to verify masses from 0.1 milligram
to 20 kilograms. For their comparison, a number of precision balances
were under construction to give the Bureau a complete series of the very best
balances possessed anywhere.
For determining the density of solids and liquids, the section had
secured two sets of Jena glass hydrometers and verified them at the Normal
Eichungskommission in Berlin. The section was working on means for
standardizing capacity measures from 1 milliliter to 40 liters and also on
* * where ordinary reading of micrometers to thousandths of an inch is pretty
generally understood, reading to 10-thousandths is not." Joseph V. Woodworth, Ameri-
can Tool Making and Interchangeable Manufacturing (New York: Norman W. Henley.
1911), p. 270.