Wichita eagle., 1888-04-13
THE THERMOMETER.
AN INSTRUCTIVE SKETCH ABOUT
A VERY USEFUL INVENTION.
Three Kinds O. Instruments In Common
Use Throughout the worId-The Fahr-
enheit Thermometer-The Zero Point.
Method of Notification.

enheit Thermometer-The Zero Point.
Method of yerifcation-
The Thermometer in its crude form was
invented by Hollander named Cornelius
Drebbel, who. it appears, made the hrst IN
strument, which he called "heat meas
urer.n in the V ear 163S. His thermometer was
simple enough. and had numerous defects,
consisting of glass bail at the top OF long
tube. the lower and open end being placed
in a vessel filed with water, colored by so
luton Of nitrate Of copper. This Instrument
was improved upon, and its defects gradually
removed by others; but it was HALEY, the
famous English astronomer, who first pro-
posed the use Of mercury as a fluid Tor the
thermometer.
There are now three kinds of thermometers
in common use throughout the world; but tie
form invented by Professor Daniel fahren-
heit, an ingenious German in the year 100,
and from whom the instrument has been
named, is the one generally employed IN this
country ana with which nearly every intel
ligent family in the land is provided, though
the ''centigrade thermometer" is really the
most convenient and is now adopted in all
countries as the standard scale for scientific
reference: and like the metric system, its
general use in this country is doubtless merely
question Of time.
Mercury boils and vaporizes at a tenpera-
ture OF 662 dogs Fahrenheit ana for obtain
ing any higher temperature than this a me-
tallic instrument called the pyrometer is
made use of, but its indications are unreh-
able, and yet it remains to discover some
moro accurate method Of measuring degrees
Of heat higher than COO degs. by the Fahren-
heit Thermometer. At a temperature OF ~
dogs. below zero mercury freezes and be-
comes solid mass malleable under the ham,
mer, and for lower temperatures, pure alec
hol spirits of wine) colored red with car
mine, is usually employed, but as in the case
Of the pryometer, its indications cannot be-
depended upon for accuracy. Fahrenheit
was not slow to recognize the advantages
possessed by mercury as fluid for the tubs
of the Thermometer. Mercury, as an excel
lent conductor of heat, is vastly more sus-
ceptible to the changes of temperature than
all other fluids. 1t is much more easily OBJ
tanned in perfectly pure state than alcohol,
which, even when prepared with the greatest
care often contains air as well as other ad-
mixtures; and alcohol is sometimes rendered
thick by great degrees of cold, and under tbs
and ununiformly.
THE ZERO POINT.
In the Fahrenheit thermometers the space
between the freezing and boiling point ot
water is divided into $50 equal parts or ds.
grees, the former being 81 dogs. and the latta
212 degs above zero, which was 50 called by
the inventor from the fact that he supposed
it to indicate the point OF absolute cold, or
! - Il, L..
duced and measured by any instrument. But
the lowest degree Of cold possible to be OBJ
tained is now estimated to be 523 dogs, and
the greatest artificial cold ever produced is
% degs by the Fahrenheit thermometer.
The zero point of a thermometer does not in
dicate the total absence of heat, as commonly
supposed and the term seems TO imply, for an
absolute zero of temperature has never yet
been attained, and has only been approx
mately determined, though it is considered
Convenient as an ideal starting point" The
zero of a Fahrenheit thermometer is the
temperature of a mixture Of ice and common
salt, which is usually employed In the opera
ton of freezing Ice cream
The zero point of thermometer should al
ways be carefully verified, unless the instru-
ment is known to be correct. To do this I'M
pounded ice, and press slightly g layer of sew
sral inches around it, so that the stem, which
should be exactly perpendicular, is covered
with snow as high as the freezing point on
the scale Do this in u room, the temperature
of which is above the freezing point, as that
point indicates the temperature of melting
snow. Then in about half an hour read it,
taking care to have the eye exactly perpen-
dicular to the column Of mercury, and NOV
ing the Thermometer freely about in the mix
ture. In case the top of the mercury and
the freezing point on the scale 90 not cor
respond, note the difference Some instru-
ments are so constructed as to admit of loos-
ening the screws and sliding the glass tube
holding the mercury up or down distance
equivalent to the error, but it is not advisa-
bic TO make frequent mechanical changes Of
this kind. The correction above indicated
should be applied to each reading Of the
scale-Arthur * Barrett in Detron Free
Press.