Savannah morning news. [volume] (Savannah) 1868-1887, 1886-05-14
MEKCURY,s UPS AND DOWNS.
Causes that Affect Thermometer
The Useful Instruments.

The Useful Instruments.
The different temperatures recorded in
various parts OF the city and the variation
Of thermometers in the same locality is
frequently matter OF discussion among
people who own thermometers. As a
matter OF course, every man insists that
his thermometer is correct and that
everybody else's Thermometer is wrong.
The not wave that swept over the
city Yesterday and sent the mer-
curry nylng up into the nineties
was the signal that the summer cam.
paign had begun. The average thermom-
eter has had an easy time of it since the
cold spell OF last January, but from now
on IL Will be mustered into active service.
mere are about as many different
kinds OF thermometers as there
are days in the year. The
prices range according to she quality Of
the instrument. Those in commoa use
cost from % cents up to 81 30, 81 or So
apiece. The majority are OF the cheaper
Kind, and for the average man who wants
one to experiment with the cheap ones
are about as good as any.
or course they vary. Out Of
every half dozen sold not more than two
will be likely to register alike. The fact
that thermometers vary is well known,
but very few people ever find out tue roa.
son. Inc officer on duty at the signal
station last night when asked for an eX-
PLANTATION said:
"Ihe principal reason is in the mperfec-
tlon OF the thermometers themselves. 1t
ID nonsense TO suppose that the cheap
thermometers are reliable. The calibra-
ton, that is. the ascerJaining Of the base
OF the tube in order to reduce it to a scale
OF degrees, IS nearly always imperfect.
ibis has 10 be very carefully done to OBJ
tain good instrument and makers can't
afford to take pains with cheap ones.
Another cause of variation is IN the
fact that the temperature Of places few
teet or few inches apart often varies
very greatly from radiation or otherwise.
FOR instance, here are two thermometers
IN this room nOtsix feet apart, and yet In
consulting them | often find a degrees
difference registered on these scales"
Everyone, almost. has remarked that
the signal service thermometer has iudi-
Gated lower temperature than private
ones scattered throughout the city. The
instruments being of the best make, all
sorts Of theories have been assigned,
said the observer; "Our thermometer
registers lower because il is so arranged
that nearly all the radiated heat is cut of.
With ordinary observers this is never
thought Of. 1t is almost impossible to find
place where more or less heat is not ra-
dIated from walls, pavements. buildings
or other objects. Consequently a Their
mometer where this is not specially pro-
vided against will always register
temperature much higher than is really
the case.
sit is extremely difficult to get the cor
rect reading of thermometer hung in the
sun, as people say. The reason is be-
cause so much depends upon the position.
Some one said to-day that street tber-
mometer marked 100 deg. 1t might have
marked ITO deg in another place at the
same time. For instance, you may go to
one of the windows when an eastern wind
Is blowing on a hot day, and the first
touch OF the current OF air on your face
will be like the breath of a furnace. 1t is
highly heated in coming over the roots OF
buildings, but its temperature will vary
in different positions. OF course, how
ever, Thermometer will always register
higher in. the sun than IN the shades' "a