Barbour County index. [volume] (Medicine Lodge, Kan.) 1880-current, 1892-05-25
MAKING A THERMOMETER.
1t Is Done Quickly, But With Great Accu.
racy, BY Nineteen Persons.

1t is Done Quickly, But With Great Accu-
racy, BY Nineteen Persons.
The making of a thermometer may
be either adelicate 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 infinitely &C
curate instrumen Is designed for scien-
tific uses great care is taken, and they
are kept in stock for months, some
times for years, to be compared and
recompared 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 carefully. The
method of manufacture has been so
systematized within a few years that
the very cheapest thermometer should
not vary more than fraction of de-
gree from the correct point
Whether the Thermometer is to be
charged with mercury or alcohol;
whether it is to be mounted in a frame
OF wood, pressed tin or brass, the pro-
cess is substantially the same. Mercury
is generally used for scientific instru-
ments, but most makers prefer alco-
hol, because it is cheaper. The alcohol
is eolored red with an aniline dive
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
proper lengths, and with his gas let
and blowpipe makes the bulbs on the
lower end. The bulbs are then filed
with colored alchohol. and the tubes
stand for twenty-four hours.
On the following day another work.
man holds each bulb in turn over a gas
jet until the colored fluid, by its ex-
pansion, 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 the
little glass hook which will help keep
the tube in place in the frame.
The tubes now rest until some hum
dreds of them, perhaps thousands, are
ready. Then the process of gauging
begins There are no marks whatever
on the tube, and the first guide mark to
be made is the freezing point. 80 de-
grees Fahrenheit. This is found bv
plunging the bulbs into melted snow.
No other thermometer is needed for a
guide, for melting snow gives invari.
ably the exact freezing point This is
an unfailing test for any Thermometer
whose 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 block of ice in
to particles, which answers the pur-
pose as well as snow.
When the bulbs have been long
enough in the melting snow a work.
man takes them one by one from their
icy bath, selling each one 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 fire ezing point
married on each, now go into the hands
OF a-other workman, who plunges
them, bulb down, into a vessel filed
with water kept constantly at "a de-
greeS A standard Thermometer at
tached to the inside of this vessel
SHOWS that the temperature of the water
Is correct Another tiny file scratch is
put at "a
Then a third workman plunges the
bulbs into another vessel of water.
kept constantly at 60 This is marked
like the others, and the tube is now
supplied with these guide marks. each
81 degrees from the next A small tab
Is then attached to each tube, on which
its number is written-for, owing TO
unavoidable variations in the bore of
the tube each one varies SLIGHTLY from
the others.
With its individuality thus establish
ed the tube goes into the hands of a
marker, who fits its bulb and hook into
the frame it is to occupy, and make
slight scratches on the frame, cor
responding to the 80 81, ami 90 degree
marks on the tube. The frame has a
number corresponding with the num-
Der of the tube, and the tube is laid
away in rack amid thousands.
The frame, whether it be wood. tin.
or brass, goes to the gauging room,
where it is laid upon a steeply sloping
table. exactly in the position marked
for thermometer of that size. The
80, Ga, and 90 degree marks must COR
respond with the marks upon the
table If they do not the error in mark
ing is detected. and the frame is sent
back for correction.
A long, straight bar of wood or metal
extends diagonally across the table
from the lower right-hand corner to
the upper left-hand corner. On the
right this works upon a pivot and on
the left rests In a ratchet, which lets it
ascend or descend only one notch at a
time, That notch marks the exact dis
lance of two degrees. with the three
scratches already made for basis the
marker could hardly make mistake
in the degrees if he tried
The marks made upon the frame or
case are all made by hand with
geometric pen and India ink if the
frame is of wood, and with steel dies If
it is of metal The tube bearing the
corresponding number is next attached
tp the frame. and the Thermometer i