The Red Cloud chief., 1899-08-04

All sorts OF instruments and appa-
'atus are used by the United States
weather Bureau to determine meteor
illogical conditions and prospects. For
measuring the exact temperature at It's
various stations are the thermograph
and the maximum and minimum Their
mometers. The former gives q con
inuous record OF the temperature: the
after " show respectively the high
st and lowest for each twenty-four
aours. For studying the pressure Of
he atmosphere, the stations OF the
Weather bureau are equipped with self
registering aneroid, paragraphs and
nercurial barometers. Readings from
both are corrected for the attitudes OF
he station. and the latter for varia-
ions In temperature. The determine
lion OF humidity. or relative humidity.
rs II Is called by the weather bureau,
3 accomplished by means OF two Their
nometers. the so-called dry-bulb and
he wet bulb. The first IL the ordi-
nary thermometer. by which the tenn
v ~ fiuituttu. tnt StCOlu IN
similar. except that the mercury bulb
Is surrounded by a cloth. which may
be saturated with water. When this IL
done, air Is made artlficially to pass
over the saturated cloth, which causes
the water to evaporate rapidly. The
heat which is rendered latent by this
process comes from the mercury of the
thermometer. making 1t descend In the
tube with a rapidity proportional to
that Of evaporation. In dry air the lat
In damp air, and by noting the differ
ence of the reading OF the dry-bulb
and wet-bulb Instruments. and making
a simple mathematical computation,
the relative humidity Ii determined. II
Is read in hundredths. 100 meaning air
saturated with moisture, and zero. air
free from II. The former point Is some
times reached. though never the latter.
The signal service makes use OF two
instruments in studying the wind-a
zane with automatic electrical indica-
tor for showing Its direction and the
thermometer for registering the veloc-
ity. Both Of these are exposed to the
u~nobstructed violence OF the wind.
though connected electrically with the
indicators which are In the Office be-
low. Both the instruments register
continually upon a drum revolved by
clockwork. and at any time the direc-
ton and velocity Of the wind can bs
seen at q glance. The apparatus used
by the weather bureau for determining
the character OF the day Is known az
the Sunshine recorder" II consists
Of n thermometer. with It's bulb black
ened to increase the absorption OF hea,
from direct sunlight. inclosed in a
vacuum tube, to prevent as far as pos
sible the direct influence OF the tenn
perature OF the surrounding air. The
piece OF apparatus Is In such a posi-
ton as to receive the suns rays the
entire day. When the direct rays
strike the blackened bulb the mercury
suddenly rises and closes an electrical
circuit, which causes a record to be
made upon the revolving drum In the
Office below. When the sun Is obscured
the mercury drops again. and the cir
cult Is broken. The computation In
tenths OF the possible sunshine hours
is made by the weather official. The
latest device used by the weather bu-
reau for measuring the precipitation
consists Of a hopper or scale pan,
which Is constructed so as to tip and
empty Itself, and ct the same tins
make an electrical indication OF the
fact in the Office below for each one
hundredth Of m inch precipitation. BY
counting these records upon the re-
volving drum the officers can tell the
exact time the rapidity and the amount
OF precipitation for each shower or pc.
Rod OF rain.