The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1903-01-04
THERMOMETER MAKING.
How the Boiling and Freezing Points
Are Found.
London Express.

The making Of Thermometer may be
either delicate scientific operation or one
OF the simplest tasks OF the skilled me-
chanic, according TO the sort of thermom-
eter made. With the extremely sensitive
and infinitely accurate instruments designed
Tor scientific uses great care is taken, and
they are kept In stock for months, some
times Tor years, to be compared and recon-
pared with instruments that are known TO
De trustworthy. But so much time cannot
be spent over the comparatively cheap Their
mometers In common use, and these are
made rapidly, though always carefully.
Mercury is generally used for scientific in
struments, but most makers prefer alcohol.
because 1t is cheaper. The alcohol is coli
ored red with an aniline dye which does
not fade. The thermometer maker buys his
glass tubes in long strips from the glass
factories. The glass blower on the PREM
ises cuts these tubes to the proper lengths.
and, with his gas jet and blowpipe, makes
the bulb on the lower end. The bulbs are
then filled with colored alcohol and the
tubes stand for twenty-four hours. On the
Following day another workman holds each
bulb in turn over gas jet until the colored
tube. 1t then goes back into the hands OF
the glass blower. He closes the upper end
and ana turns turns the tip backward to make a
little glass hook, which will help keep the
tube in place in the frame
The tubes rest until some hundreds of
them, perhaps thousands, are ready. Then
the process OF gauging begins. There are
no marks on the tube, and the first guide
marks TO be made is the freezing point y
degrees Fahrenheit. This is found by plung-
ing the bulbs into melting snow. No other
thermometer is needed for a guide for melt
ing snow gives invariably the exact freezing
point. This is an unfailing test for any
thermometer when accuracy LAY us So
pected. But melting snow is not ALWAYS 10
be had, and little machine resembling a
sausage grinder is brought into use This
machine shaves block OF ice into particles
which answer the purpose as well as snow.
When the bulbs have been long enough in
the melting snow workman takes them
one by one from their bath, seizing each so
that his thumb nail marks the exact spot
to which the fluid has fallen. Here he makes
a scarcely perceptible mark upon the glass
with fine file. and goes on TO the next
The tubes, with the freezing point marked
on each. now go into the hands OF another
workman, who plunges the bulb into a YES
sci filled with water kept constantly at 8,
degrees. Another tiny fle scratch is put
at "a degrees.
Then Il third workman plunges the bu,hs
into another vessel of water kent constant
ly at So degrees. This Is marked like the
others. and the tube Is now supplied xith
these guide marks, each 81 degrees from
the next.
With its individuality thus establishes
the tube goes into the hands Of a marker
who fits its bulb and hook into the frame
IL Is to occupy and makes slight scratches
on the frame corresponding to the % e
and S6-degree marks on the tube
The frame, whether IL be wood. tin or
brass. goes to the gauging room. where il
is laid upon a steeply slipping table marked
exactly In the position for Thermometer
of that size. =
A long straight bar OF wood or metal ex-
tends diaeonaily across the table from the
lower right hand corner to the upper left
pivot, and on the left II rests I'M a ratchet
which let's Il ascend or descend only one
notch at a time. Each notch marks The
exact distance OF de<rees~