The National tribune., 1891-02-05
THE WEATHER.
The Measurement Of Atao.alsrle Temperate
ny LIEUT.. ). r. FINLEY, .. q SIGNAL SERVICE


Correspondence invited. suggestions desired.
and Information cheerfuly furnished Every ef-
Tort employed TO make this Bureau Of practical
10 the readers Of THE NATIONAL TRInUyE. All
communications should be Weather
iHE NATIONAL TRIBUNE Office, Washington. ID. C.l
The public generally do not comprehend the
Importance OF careful exposure of instruments
IN ascertaining the temperature of the air. A
thermometer suspended anywhere out OF doors
where it will not be injured, appears to answer
the requirements Of those W 10 are unacquainted
with the manner in which the instrument is
affected by its surroundings.
In many instances those people who are most
careless about the proper exposure of Their
mometer are most querulous about the differ
enees IN readings of different instruments, in-
sisilng That the one they are especially inter
ested in is doubtless correct neglecting entirely
the influence Of surroundings.
In the preparation Of the daily weather map
ana the study Of storm development for the
purpose Of weather fOrecasting. thermOmetric
observations must be carefully guarded and
accurately measured. A little reflection will
convince an intelligent person that for such
work the temperature OF the free air must be
obtained. The best instruments must be en-
poyed and the most careful exposure secured.
without proper exposure the most elaborate and
costly thermometer becomes useless for satisiac-
tory observation. IL the instrument at a station
ISIS located as TO indicate the temperature of the
hot air from a live chimney or furnace, or
radiation from surrounding objects under the
direct rays OF the sun, II il quite patent that
the measurement Of such instrument could not
DC relied upon as giving the temperature of the
air. To base weather forecasts on such records
would involve certain failure. The readings
from instruments so exposed could have no
scientific or practical value so far rs meteOrO-
logical work is concerned.
Even for commercial purposes or 10 crafty
curiosity thermometer should be exposed so
as to Indicate as far as possible the temperature
OF the free air. Theoretically speaking a per-
feet exposure is quite impracticable.
The best results are obtained by placing the
instruments IN lower boarded box. having a
double roof the space between the two cover
ings being about 10 inches. with openings on
the sides for the free movement Of the air in
all directions. The ceiling of the lower roof
immediately over the instruments should DO
tight. as also the floor Of the shelter below
The louver-boarled sides NAV 10 double or sim
gle. in the former case sloping in opposite
directions. Such screen or shelter, as il is
called, should not be less than Is inches square
inside measurement, aud two feet would be
better
In cities this shelter may be placed at the
north window of a building or upon the roof.
Ia the former case the instrument should be
the frame. as the Instruments would be affected
by the heat of the body and the warm air from
tho room. If placed upon the roof the shelter
must be raised upon a light derrick that will
lift tho bottom OF the box at least 10 feet above
the surface OF the roof. A ladder placed against
the derrick, or made part Of IT. will be necessary
10 reach the instruments for observing them.
The door of the shelter sliould face north and
the instruments be supported on a suitable
framework placed in the center Of the box.
In the country the shelter should be placed
on derrick four to 10 feet above ground we'll
covered with grass, free from the shadow of
trees or buildings. and not within 20 feet Of
any wall. A window shelter affords the least
favorable exposure Of the three plans here
given, and should not be employed when either
OF the other two is available. In all eases care
must be taken 10 avoid live ehimneys steam
pipes or any object so near as TO radiate its
heat upOn the shelter