The Brandon news. (Brandon, Miss.) 1892-1961, 1903-03-12
THERMOMETER MYSTERIES.
How the Boiling and Freezing Points
Are Found.

HOW the Boiling and Freezing Points
Are Found.
The making of thermometer may
be either a delicate scientific operation
or one of the simplest tasks of the
skilled mechanic, according to the sort
OF thermometer made. With the ex-
trcnely sentative and infinitely accu-
rate instruments designed for scien-
tile uses great care is taken, and they
are kept in stock for months, some
times years, to be compared with in
struments 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 always
carefully,
Mercury is generally used for scien-
tific instruments, but most makers
prefer alcohol, because it is cheaper.
The alcohol is colored red with ami
line dye, which does not fade. The
thermometer maker buys his glass
tubes in long strips from the glass
factories. The glassblower on the
premises cuts these tubes to the prop
er 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 "a 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. 1t then goes back into the hands
of the glassblower. He closes the up
per end and turns the tip backward
to make the 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 mark to be made is the
freezing point, 80 degrees Fahrenheit
This Is found by plunging the bulb
into melting snow. No other Their
mometer is needed for guide, for
melting snow gives invariably the eX-
act freezing point This is an unfail-
ing test for any thermometer when ac-
curacy may be suspected. But melting
snow is not always to be had, and a
little machine resembling a sausage
grinc er is brought into use. This ma
chino shaves a block of ice into par
ticles, 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, Selling each one so
that his thumb nail marks the exact
spot to which the fluid has fallen. Here
he makes 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 vessel filled with water
kept constantly at ga degrees. An
other tiny scratch is put at Ga degrees.
Then third workman plunges the
bulbs into another vessel of water,
kept constantly at Sc degrees. This is
MARRIED like the others, and the t':b,
is now supplied with these guide
marks, each 80 degrees from the next.
With it's individuality thus estab-
lished, this tube goes into the hands
of a marker, who fits its bulb and
hook into the frame it is to occupy
and makes slight scratches on the
frame corresponding to the 80 degrees,
Ga degrees and Sc degrees marks on
the tube.
The frame, whether it be Of wood,
tin or brass, goes to the gauging room,
where it is laid upon steeply sloping
table, marked exactly in the position
for a 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 it rests in a ratchet, which
lets it ascend or descend only one
notch at time. Each notch marks
the exact distance of two degrees
London Express