Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-01-02
vious to taking II. such as halls, frostr,
aureras, hot and cold spellF,

.
auroras, hot and cold spellr,
THUNDER AND LIGHTNING,
Earthquakes, flight of birds, leaving of trees,
poisoning of flowers, aud everything thst
tends to complete the climatic condition of
the place of observation at that particular
time. An observation with the instruments
commences first with the barometer, the read.
lngs OF which are recorded in inches and
hundredths, which is afterwards corrected
for temperature, instrumental error and
elevation. We correct for temperature, be-
cause heat expands the column of mercarv
therefore requiring greater hight to produce
given pressure /; also for the purpose Of com
pairing all barometric readings. For all scien.
tifc purposes the readings of the barometer
in all countries must be such as to be COM
pared to certain standard of temperature :;
the temperature therefore sgreed upon is that
of melting ice. Our barometric readings is
reduced to temperature of 32o, which is
that of melting ice. We correct for
instrumental error whenever there is q
difference in the readings of a barom-
eter, when it is compared with the
standard barometer at the Chief Signal
Office, Washington, D. G. Ii it reads less
than the standard, we add the mean differ
ence; if it reads more, we subtract. The
difference is usually small. We subtract
from the barometer at this station 001) one
thousandth of an inch after the barometer
has been corrected for temperature. The
baroxnetric readings are now corrected for
temperature and instrumental error.
THE CORRECTION FOR ELEVATION
Is next applied We correct for elevation
because the stratum Of air resting ON the
earth's surface, between all stations and the
level of the sea, is that much less atmosphere
pressing on the mercury in the cisterns of the
barometers at stations above the sea level.
The cistern of the station barometer at this
place is 60 6 feet above sea level. We there
fore correct for that much elevation-that is,
we add .070 of an inch in summer and 0S0
of an inch in winter to the barometer after
it has been corrected for temperature and
instrumental error. The barometer il now
corrected for temperature. instrumental errCr
and elevation, which is the reading tele-
prsphed three times daily TO the Chief Signal
Office at Washington. The thermometers
are next consulted, which ara kept in an in
strument shelter. The shelter is double
latticed frame work, permitting Tree circu-
lation of air, and fastened to a window
which must invariably face the north. The
instr ruments are constantly in the shade and
elevated above the sidewalk about 81 feet.
and distant from the window about ore foot.
The maximum thermometer is Thermometer
like others in use, with this difference, viz /:
near the bulb the bore is made somewhat
smaller; heat expands the mercury in the
bulb more than it does the glass. the mercury
is forced up through the slnaller aperture,
and indicate
THE HIGHEST TEMPERATURE
During the day. When it begins to grow
cooler the mercury in the bulb contracts, and
the mercury in the tube would recede towards
the bulb were it not for the smallness of the
tube near the bulb; therefore it remains
above the small aperture, and shows the
highest point reached by the Thermometer
during the day. This thermometer is always
kept in a horizontal position by means of a
brass pin. At II P. N Washington time,
which is S.02 p. NJ. local time, each day, the
thermometer is set by turning it around on 3
pivot By centrifugal force, or the force of
the revolution, the mercury is thrown back
again into the bulb, until the thermometer
corresponds with the temperature Of the air
at that particular time. The minimum ther-
mometer is spirit one (alcohol), which is also
kept in horizontal position. Within the
tube of the minimum is placed very fns
glass rod, about half an inch in length aud a
little smaller than the bore of the tube. This
index is immersed in the column of alcohol,
but must be brought in contact with the ex-
tfSUl1Gy OF LIE Ou dCCOunB OF
the capillary adhesion between the al
cohnl and the glass, when the alcohol
contracts by cold. it drsgs along with it the
glass index but when the alcohol expands by
heat it passes by the index without displacing
it; SO that the position of the index shows
the lowest temperature to which this ins.ru-
ment has been subjected since the last OBJ
servation An observation OF both the maxi
mum and minimum thermometer is made
once day. at II P. NJ. Washington time and
S:02 P NJ. Sacramento time, at which time
they are both act, the maximum as above de-
scribed, and the minimum by raising the bulb
end to early rpendiculsr position. The
iedex will run down to that OF the top Of the
column of alcohol at whatever temperature it
then stands at.
The following tables give the mean annual
barometer, mean thermometer, maximum and
minimum, for the different seasons of each
year from 1873 to 1882: