JANUARY 5, 1912] 
the federal government and for the states 
and state institutions free of charge. For 
municipalities and corporations and indi- 
viduals fees are charged, which in most 
cases scarcely cover the actual cost of the 
test, but which are high enough to exclude 
tests of small importance. In some eases 
the bureau declines to make tests, as, for 
example, when it is believed that the pro- 
posed test would not settle the question at 
issue, or where the work would be incom- 
mensurate with the value of the result, or 
where the test is simple and could be done 
as well elsewhere, and, of course, whenever 
the facilities or experience of the bureau 
are not sufficient to warrant attempting the 
work, or where the work already on hand 
is too great to permit it. But with these 
eases excluded, there remains a great va- 
riety of tests in all divisions of the bureau, 
which are being done for the government 
and the public, and many of these tests 
are of great practical importance. The 
fees charged are smaller than they would 
be if the tests were not generally of 
value to others besides those who pay for 
them. Most private tests, indeed, are 
of public advantage. For example, it is 
of public concern that manufacturers of 
electrical instruments have their stand- 
ards tested at the bureau, as this tends 
to insure greater accuracy in the instru- 
ments sold to the public, without add- 
ing appreciably to the cost. That electric 
lighting companies have their test meters 
and voltmeters standardized and gas com- 
panies have their meter provers and photo- 
metric or calorimetric standards tested is 
a matter of public concern, for it improves 
the service rendered to the public. If 
manufacturers of electrical machinery 
have insulating materials tested for re- 
sistance and dielectric strength, and sheet 
iron and castings tested for magnetic 
quality, and copper tested for conductiv- 
SCIENCE 15 
ity, their customers get better machines, 
and the public better service. 
Electrical instruments tested by the 
bureau include standards of resistance and 
electromotive force, and precision resist- 
ance apparatus of all kinds; condensers 
and inductances of various kinds used in 
laboratory measurements and in radio- 
telegraphy, both commercial and experi- 
mental; ammeters, voltmeters, wattmeters, 
watt-hour meters and many other kinds of 
measuring instruments, for direct or alter- 
natmg current; instrument transformers 
for current and voltage, including those 
for very heavy currents and high voltages; 
magnetic instruments; photometers, and 
various kinds of photometric standards, 
electric and gas, locomotive headlights, in- 
eluding oil, acetylene and electric; signal 
lamps, street lamps, ete. 
Materials tested include copper, alu- 
minum and other wires used as conduct- 
ors of electricity; manganin, constantin 
and other alloys for resistance, thermal 
electromotive force, ete.; iron and steel and 
other magnetic or slightly magnetic mate- 
rials for permeability, hysteresis, coercive 
force, ete.; sheet steels for iron losses due 
to alternating magnetizations; insulating 
materials for instruments and electrical 
construction; electric lamps for candle 
power, efficiency and life, and for the 
quality of the light furnished; oils to be 
used in standard lamps or as illuminant or 
for signal purposes, ete. 
These tests of instruments and materials 
are sometimes made for the purpose of see- 
ing whether they conform to the specifica- 
tions under which they are sold, sometimes 
for the information of the manufacturer of 
the given instrument or material, some- 
times for the information of an intending 
purchaser, often for the purpose of re- 
standardizing the instrument for regular 
service. A great deal of time is required 
to keep the equipment employed in testing 
