Evening star., 1900-10-13
instruments to Weigh a Zephyr or
Measure a Hairbreadth.
CARE USED IN HANDLING TEEN
How the Original Meter and kio-
gram Are Preserved.
DELICATE OFFICIAL SCALES
Copyright, 1900, by II. G. Gardner. }

4
Written for The Evening Star by H. ellison Gardner
In the windowless basement room, origi-
nally built for coal vault Of IN old man.
sion near the Capitol is mounted the most
delicate pair of scales in the United States.
TO these scales are intrusted the work of
Going the governments weighing. They
are part or the equipment of the Treasury
Departments bureau of weights and meas
ures which is attached to the coast sur
vey. though why this should be so nobody
has ever adequately explained.
So delicate are these scales that they
will weigh accurately a ten-millionth part
of gram. They are so sensitive that the
warmth given off by the body Of a person
approaching them near enough to open
the glass or to shift the weights
would expand the balance arms and pro-
3" duce an appreciable error in the results.
Therefore they have been so constructed
that they may be operated at a distance
OF twenty feet. 1t is not necessary to open
the case or to go near the machine even to
shift the weights. Three long brass rods
extend from the base of the case contain
ing the scales. and at the extremity of
each is wheel, so that by turning these
wheels the weights may be shifted from
one pan to another any other necessary
operations conducted. The readings are
made through small telescope mounted
where the operator stands.
Too late 1t was discovered that the
adjustment of the instrument in corner
of the room was mistake. The fact that
one wall is three feet away and the oppo-
site one nine feet has a marked effect on
the scales. On the side where the wall is
close the temperature is different from
the other side, and whenever the instru-
ment is used it has been found necessary
to surround 1t with large sheets of asbestos
paper. Besides this, the attraction of the
wall for the metal in the scale beams has
to be taken into account
Minute Differences in Weight
But these are only a few of the things
which have to be allowed for in doing a
fine job of weighing. Large corrections
have to be made for the temperature,
humidity and density of the air. With each
weighing there must be a reading of the
thermometer, barometer and hydrometer,
and corrections to correspond to the cond-
tons existing at the time. In Germany
there are scales built that the weighing
can be conducted in a vacuum; but this
government owns no such apparatus.
Incredible as it may seem, the difference
of an inch or two from the center of the
earth, thousands of miles away, constitutes
an appreciable variation in the weight of
the objects. This is illustrated by placing
| two equal weights side by side in each pan,
when the beam shows no variation. But
place of the weights on top of the
other in one pan, leaving the other pain
side by side in the other pan, and the bal
ance will be disturbed, the weights which
are side by side appearing the heavier. be
cause of the increased distance from the
center of gravity of one of the weights.
The weights used in this experiment are
scarcely two inches in height, that the
difference in distance from the earths CEN
ter, considered in comparison to the dis
tance itself, Is infinitesimal.
A still further allowance is demanded by
scientific accuracy Even in a fifteen hun
1 dred-doliar Rupbrecht instrument, like the
one owned by the government bureau 1t is
not pretended that the two arms of the bal
ance are of the same length. Official Neri-
tier Frank A. Wolff says no scales were
ever built In which the arms We're of ex-
actly the same length. The only thing to
do, therefore, Is to check up the error by
weighing alternately on side and the
other, and then averaging the results
Standards OF Length and Mass.
The original fundamental prototypes
from which all measures of length and
mass are derived are stored in the same
building near the Capitol. The standard or
mass is a cylindrical shaped piece of whit
ish metal about the size of a tennis ball.
The standard of length is a bar of the same
silver-iike metal about three feet long and
a little less than inch square. Each
face is deeply grooved. and in one of the
grooves at either end is polished spot on
which three delicate hair lines are marked.
The middle one OF these lines determines
the end of the bar. The bar Is standard
meter. and the cylindrical weight Is the
which they are made Is a mixture of plati-
mum and Iridium, the latter being added to
give additional hardness to the metal which
above all others Is recognized as the most
durable. The value of the metal alone in
this prototype of the standard meter is
over $1,000, but 1t has much greater
value from the labor expended in making
ft perfectly accurate. The kilogram and
meter prototypes the result of fifteen
years labor by joint congress Of scien-
lists, supported by seventeen of the leading
rfIr ha int me frio
convention was organized in 1873 and on
January ., 1890, the President of the
United States broke the seal of the stand
ard kilogram and meter which fell to the
share of this country, and in the presence
of the Secretary of the Treasury and a
number of invited guests, assembled in the
cabinet room of the Executive Mansion,
declared them officially adopted.
Preserving the Originals.
These originals have been used but once
since. This was when very accurate copy
was made from each for practical use by
the government bureau in regulating the
standard weights and measures of the
country. The original kilogram was then
placed under two glass bell-1ars which
were locked and sealed. No human hand
has touched the kiogram since 1t left the
makers in Paris; what little handling has
been necessary has been done with pair
of special forceps covered with soft chamo1s
skin. This is to prevent increase or weight
| eign substances, or decrease of weight by
| an abrasion. 1t has not been found neces-
sary to exercise an equal degree of care in
preserving the standard meter; little mois-
ture or dirt would not lengthen or shorten
the metallic bar. Nevertheless, it is kept
in case of velvet surrounded with wood
and protected theioutside by heavy
iron cylinder with a screw tap, 1t is re-
moved only on special occasions.
The only generally legal standard of
weights and measures in the United States
ic he atrin yy,fa IL
gress passed an eact making the metric sys-
tenn lawful throughout the United States
and defining the weights and measures in
common use in' terms of the units /of this
system. The government mint, however,
has a system of tits own BY a special act
of Congress passed in t1S2S the Troy pound
was made the standard for weighing the
government bulHon, and a prototype OBJ
tanned the previous year from London. and
made by Gallatin. was declared standard.
Supplying the States.
Although there has been no adequate
legislation on the subject, the government