Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-04-09

of the other rooms where close work is
done, is kept at a temperature of just 20
degrees. The reading of a measure, be 1t
steel tape or anything else. is made at
that temperature; and there is a correction
scale sent out with the instrument when
it is standardized, giving the coefficient of
expansion or contra ctton at temperatures
above or below 10.
Thus it will be seentha swhen an instru-
ment has once BEEN standardized by the
bureau and the exact feerfection made for
1T the worker who uses it has practically
perfect instrument, for all that is neces-
sary is to add to or subtract the correction
from the reading of the instrument and it
gives the exact figure, as close as human m
mometers, steel tapes, meters for gas, water
or electricity or any7 of 8he other many
instruments with which the bureau deals.
OF course it is not intended to standard
ize every individual !, instrument in the
United States, but a big manufacturer of
thermometers, steel tapes, mathematical in
Struments or scales can send his standard
instruments to the bureau. have them
standardized and returned TO him. SO that
he knows he has q Thoroughly reliable
standard instrument IN his shop by which
to gauge the thousands of instruments he
makes and sends out TO purchasers.
Measuring Temperatures.
AT the same time there is a great deal of
individual standardizing done by the
bureau. Clinical thermometers are tested
by the tens of thousands annually. They
are submerged with an absolutely accurate
standard thermometer in water which is
heated through varying temperatures and
kept in motion by little electric agtator.
The thermometer comes out of the ordeal
corrected to the Tooth of n degree. OF
course, the correction could be carried
further than that, but there are few nurses
or physicians who can read clinical
thermometer to one-tenth of a degree, so
Tooth is considered close enough
But clinical thermometers, while they are
one of the commonest sorts of temperature
meters that the bureau has to deal with,
are not the only ones by any means.
There are high temperature thermometers
of hard glass with nitrogen under pressure
above the mercury column. These VIII
read up to 1000 degrees Fahrenheit, and
there are still higher temperature Their
mometers, called promoters, made of plat
mum and other metals, registering up TO
$500 degrees Fahrenheit. Then there are
optical thermometers for measuring the
temperature of the hottest furnaces or even
approximately the temperature of the cleo
trio arc, the greatest heat that can be arti-
fcially produced, namely, about 100
Fahrenheit.
These higher scale thermometers, while
they are and costly, are largely used
for scientific research in technical laborato-
rieS, In manufactures and In anneallng 1ur-
naces. They are therefore most important.
On the other hand, there are thermometers
for registering tempera lures far below the
freeZlnS point Oh mercury, tneffnofneterS
using pentane, copper constantan or helium
gas, which is the only substance known not
solidfied at the temperature of solid hydro
gen. These wonderful instruments will reg
lister temperatures to within 16 degrees of
the absolute zero. or about 430 degrees
Fahrenheit below the freezing point of
water This is wide range of tempera-
ture For the higher ones the bureau is
equipped with all sorts of furnaces and gas
and electric machines. For the lower ones
it is necessary to use liquid air. An ap-
paratus which produces liquid air in larger
iStence has JUST been bought at the St |