The Virginia enterprise., 1903-02-20
THERMOMETER MAKING.
How Boiling and Freezing Points Are
Found and Degrees Marked.

= II
The making Of q thermometer may be
either delicate scientific operation or
one Of the simplest tasks Of the skilled
mechanic, N according to the sort Of
sensitive. and minutely accurate instru-
ments designed for: scientific uses great
care is taken and they are kept in stock
Tor months, sometimes years, to be COM
pared with instruments that are known
to- be trustworthy. But SO much time
cannot be spent over the comparatively
cheap thermometers in common use, and
these are made rapidly, though always
Mercury is generally used for scientific
instruments, but most makers prefer al
cohol because it is cheaper. The alcohol
is colored red with 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 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 filled 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
1uid by it's expansion entirely fills the
tube. It then goes back into the hands
of the glass blower. He closes the upper
end and turns the tip backward to make
little 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 thermometer is
needed for a guide, for melting snow
gives invariably the exact freezing point.
This is an unfailing test for any therme-
but melting snow is not always to be
had and a little machine resembling a
sausage % grinder is brought into use.
This machine shaves block of ice into
tHn,5 PaI,15lcies' whlcn answer 7s the purpose as
been long enough in the melting snow a
workman takes them one by one from
their bath, seizing each so that his thumb
na!i marks the exact spot to which the
tuld has fallen. Here he makes
scarcely perceptible mark upon the glass
The tubes, with It'll the the freezing t ri qEe point point
marked on each, now go. into the hands
| OF another workman, who plunges the
bulb into vessel filled with water kent
constantly at 96 degrees. This is marked
l1n,,id1 nKe the .;1s Others and the tube, is now
81 degrees from the next.
With it's individuality thus established.
| the tube goes into the hands of a marker.
who fits it's bulb and hook into the frame
it is to occupy and makes slight scratches
on the frame corresponding to the
~ degrees, 81 degrees and 96 degrees
| marks on the tube.
The frame, whether it be wood, tin OF
brass, goes to the guaging room, where
it is laid upon steeply sloping tabl.,
marked exactly in the position for a
thermometer of that size.
A long, straight bar of wood or metal
extends diagonally across the table from
the lower right-hand corner to the upt,er
left-hand corner. On the right this rests
upon pivot and on the left it rests in a
rachel, which let's it ascend or descend
only one notch at time Each notch
MARKS the exact distance Of two degrees.