The Savannah morning news. (Savannah, Ga.) 1900-current, 1902-11-13
THERM0M ETER- MAKING
MYSTERIES
How boiling and Freezing Points
Are Found and intermediate De-
Erees Are Marked.
From the London Expre.


From the London Express.
The making of thermometer may
be either delicate scientific operation
or one Of the simplest tasks of the
skilled mechanic, according to the sort
of thermometer made. With the ex-
tremely sensitive and minutely accur-
ate instruments designed for scientific
uses great care is taken, and they are
kept in stock for months. sometimes
years, to be compared with instru-
ments that are known to be trust
worthy. But so much time cannot be
spent over the comparatively cheap
thermometers in common use. and
these are made rapidly, though al
ways carefully.
Mercury is generally used for scien-
tli1c instruments but most makers pre-
fer alcohol, because it is cheaper The
alcohol is colored red With aniIine dive
which does not fade. The thermorn-
eter maker buys his glass tubes In
long strips from the glass factories
Inc glass blower on the premises 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 filed with colored alcohol
and the tubes stand for twenty-four
hours. On the following day another
workman holds each bulb in turn over
a gas jet until the colored fluid by its
expansion entirely fills the tube. II
then goes back into the hands of the
glass blower. He closes the upper end
and 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 marl@ on the tlrbe. and
the first guide mark to be made is the
freezing point, 80 degrees Fahrenheit.
This is found by plunging the bulbs
into melting snow. No other thermom-
eter is needed for a guide, for melting
snow gives invariably the exact freez-
ing point. This is an unfailing test
for any thermometer when accuracy
may be suspected. But melting snow
is not always to be had, and a little
machine resembling a sausage grinder
is brought into use. This machine
shaves a block of ice into particles
which answer the purpose as well as
snow. When the bulbs have been
long enough in the melting snow a
workman takes them one by one from
their bath, Selling each so that his
thumb nail marks the exact spot to
which the fluid has fallen. There he
makes a scarcely perceptible mark up
on the glass with a fine file. and goes
on to the next.
The tubes, with the freezing point
marketed on each, now go into the
hands of another workman, who
plunges the bulb into vessel filed
with water kept constantly at Ga de-
grees. Another tiny file scratch Is put
at 81 degrees. r.
Then third workman plunges the
bulbs into another vessel of water kept
constantly at So degrees. This is marked
like the others, and the tube is now
supplied with these guide marks, each
81 degrees from the next.
With its individuality thus establish
ed, the tube goes into the hands of a
marker who fits its bulb and hook IN
to the frame it is to occupy and makes
slight scratches on the frame corre-
spending to the 80 degrees, Ga degrees,
and SO degrees marks on the tube,
The frame, whether it be wood tin,
or brass, goes to the gauging room,
where it is laid upon a steeply STOP
ing table marked exactly in the posi-
ton for Thermometer of that size.
A long, straight bar of wood or met
al extends diagonally across the table
from the lower right hand corner to
the upper left hand corner. On the
right this rests upon a pivot, and on
the left 1t rests in ratchet, which let's
1t ascend or descend only one notch at
a time. Each notch marks the exact
distance of degrees.