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

108 ELECTRICITY, RAILROADS, AND RADIO (1911-16)
The silver voltameter used to determine a new value for the international ampere. The
experiments at Washington in 1910 made it possible to assign mutually consistent
values to the standard cells and standard resistors used in the respective national
standardizing laboratories, in terms of the resistivity of mercury and the electrochem-
ical equivalent of silver. The units thus established formed the basis for all electrical
measurements throughout the world for the next 37 years.
approved and the sum of $175,000 appropriated for its construction. As
East building, it completed the quadrangle on the hilltop, and Rosa and his
division moved in during the spring of 1913.10
Useful and even necessary as the new international values were to
electrical science and industry, they were, as Stratton had said, far from per-
manent. Continued research in instrumentation and procedures resulted
in greater refinements of the values and the standard resistances and stand-
ard cells slowly began to drift. By 1925, serious discrepancies were evident
among the standards maintained in the national laboratories here and abroad.
Where measurements had been made with once satisfactory accuracies within
a few parts in 100,000, certain of them could now be kept constant within a
few parts in a million. There was need for agreement on the new values
possible.
10 The building was accepted in June 1913 but not actually completed until several
months later, after members of the electrical division themselves installed the wiring.
See correspondence in NBS Blue Folder Box 77. That wiring was still functioning satis-
factorily when it was replaced with modern fireproof conduits in the 1950's (interview
with Dr. F. B. Silsbee, Jan. 29, 1963).