Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1895-12-08
INTERIOR OF THE BUREAU.
CJercurial barometer Being Ready


matter repeatedly before the Chief Of
the Weather Service the boey was prom
ised an observer If proper accommoda-
lions were afforded him. Quarters were
at once provided, and Mr.. Evans, one or
the most efficient and competent men IN
the service, was placed in charge OF the
bureau.
While Mr. Evans Is only partially in
stalled as vet, he is making two readings
day of the temperature, wind, rainfall
sun rays. clouds, etc, and these readings
are being duly forwarded 70 the chlei bu-
reau, at Washington. and sent all over
the country. Mr.. Evans also makes up a
monthly report, embracing all obtainable
facts concerning the weather throughout
Virginia.
A MERCURIAL BAROMETER.
Mr.. Evanss Office is soon 70 be supplied
with the most improved and modern APP
planes for reading or observing the
conditions Of the weather. One Of the
instruments used will be a mcrcurial
barometer, which is designed TO give the
weight OF the air. This is about 80 inches
high, filed with sufficient mercury 20
exactly counterbalance the weight Of the
air AS this weight increases or dmin-
ishes the column of mercury rises or
falls, the amount of the change being
ascertained by the adjustment and read
ing Of the fixed and movable scales at the
top of the instrument. BY its use tnior-
nation is obtained as to The approach Of
storms or fair weather. The barograD h
is what its name implies-a barometer
which writes or traces n record OF the
rise and fall Of the atmosphere.
MANY THERMOMETERS
In Mr.. Evanss work he uses a number
of thermometers. First is the exposed,
which gives the actual temperature Of the
air--that Is, the temperature at what
ever time it is read. Next IS the wet
bulb. This IS the same in appearance and
construction as the exposed, except That
the bulb Is covered with muslin, which,
at the time Of observation, j. saturated
with water, and whrled rapidly on ma
chine constructed for that purpose, IN
order TO obtain the temperature Of the
deW-point, and the relative humidity.
Then comes the maXimum thermometer,
from which is obtained the highest tenn
perature during each tWenty-fOur hours,
and the minimum thermometer. which
gives the lowest temperature in each
twcnty-four hours These instruments are
what are known as self-recOrding In the
case OF the maximum the mercury, owing
TO expansion from heat, Is forced from
the bulb through a construction in the
tube near the bulb and on up the instru-
ment, until the greatest period Of heat
for the day has been reached, at which
pOint it remains until set for the next
maximum reading. This is done By whirl-
ing it rapidly on a brass pin, which
forces the mercury back through the con-
striction into the bulb.
MINIMUM THERMOMETERS.
The minimum thermometer IS filed with
alcohol. In the tube is inserted a slender
steel index about an inch long. in appear
ance like a piece Of horsehair, with the
ends slightly enlarged. The alcohol flows
| freely past this index as the temperature
rises. but as soon as it grows colder, and
! the alcohol recedes. it carries this index
! along with II until it reaches the lowest
or minimum, temperature. at which point
! ii remains until set for the next reading
| This Is done by elevating the bulb end
/ OF the instrument until the index moves
10 the end Of the alcohol column.
Both the maximum and minimum
| thermometers rest in nearly horizontal
| position.
READING THE WIND.
The direction OF the wind. rate at which
! IL IS moving rainfall. and sunshine, are
/ all recorded electrically by one instru-
| ment, known as the self-register, al
1 though each element is obtained by a
! separate instrument specially designed
| for that purpose. Thus, for the wind d.
| recti0n a vane is used which. by means
| Of proper contacts. is made to register
the point from which the wind Is blowing.
| once each minute. In the same way,
| the velocity at which the wind is trav-
cling is obtained by means Of four hem