Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-02-14

W.. .N| But so much time
.| cannot be spent over
~ the com para lively
cheap thermometers
In common use, and these are made RAPIDLY.
though always carefully The method Of
manufacture has been so systematized with
In few years that the very cheapest ther-
mometer should not vary more than frac-
tion OF degree 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
orass, the process is substantially the same.
Mercury is generally used for scientific in
strunents, but most makers prefer alcohol,
because it is much cheaper The alcohol il
coiored red with an aniline dye which does
Work OF the Glassblover.
Ihe thermometer maker buys his glass
tnoes In long strips from the glass factories.
Inc glassolower on the premises cuts thess
tubes In the proper lengths, and with his
gas Jet and blow pipe makes the bulb on
tne lower end. The bulbs are then filled with
eoloreo alcohol, and the tubes stand for "a
nours. On the following day another work.
until the colored fluid, by its expansion. en-
tIreiy nils the tube. It then goes back into
tne hands OF the glassblower 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.
Ihe tubes now rest until some hundreds
OF them, perhaps thousands, are ready
Then the process of gauging begins. Theirs
are no marks whatever upon the tube.
nothing to show the temperature of the
atmosphere, and the first guide mark to be
MADE Is the freezing point, 80 degrees
Fanrennelt This Is found by plunging the
bulbs into melting snow. No other ther-
mometer is needed here for a ouide for
melting snow gives invariably the exact
1reezlng point. This is an unfaiIing test for
any Thermometer whose accuracy may be
suspected But melting snow is not always
10 De had, and little machine resembling
a sausage grinder is brought into use. This
machine shaves block of ice into fieecy.
snow-l1ke particles, which answer the pur-
pose as well as snow
Getting the Freezing Point.
When the bulbs have been long enouph
in the melting snow a workman takes them
one by one from their icy bath, seizing 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 a fine file, and goes on to the
next.
The tubes, with the freezing point marked
upon each, now go into the hands of another
workman, who plunges them, bulb down,
into vessel filled with water, kept con-
stantly at 64 degrees. A standard thermom-
eter attached to the inside of this vessel
ahows that the temperature of the water il
correct. Another tiny scratch is put at 64.
Then third workman plunges the bulbs
into another vessel of water, kept constantly
st SO. This is marked like the others. and
the tube is now supplied with these guide
marks, each 30 degrees from the next. A
mail tab is then attached to each tube, on
which its number is written, for owing to
variations in the bore of the
lube each one varies slightly from the other.
With its individuality thus established
he tube now goes into the hands of
marker, who fits its bulb and hook into the
rame it is to occupy, and makes slight
scratches on the frame, corresponding to 80,
a and 90 degree marks on the tube. The
rame is given q number corresponding
With the number of the tube, and the tube
S laid away in Q rack amid thousands Of
,thers.
Marking on the Degrees.
The frame, whether it be wood, tin or
,rass, goes to the gauging room, where it is
aid upon steeply-sloping table, exactly in
he position marked for thermometer Of
hat size The 50, 64 and 96 degree marks
must correspond with the marks upon the
able; if they do not the error in marking in
instantly detected, and the frame is sent
ack for correction.
A long, straight bar of wood or metal er-
ends diagonally across the table, from the
over right-hand corner to the upper left
and corner. On the right this works upon
pivot and on the left it rests in rachet.
7hich lets it ascend or descend only ono
otch at a time. That notch marks the exact
istance of two degrees. With the three
cratches already made for basis the
larker could hardly make mistake in the
egrees if he tried.
The marks made upon the frame or case
re all made by hand with geometric pen
nd India ink if the frame is Of wood, and
ith steel dies if it is of metal.
The tube bearing the corresponding num-
er Is next attached to the frame, and the
thermometer is ready for the market with
at further testing Some makers use only
20 guide marks but the best makers use
Tree.
In the process of manufacture the ordin-
" Thermometer goes through the hands Of
workmen, half of whom are often girls
I'd women.
Some of the larger concerns in and ncar
ew York produce several hundred thou
nd instruments annually, and on every
le of them the purchaser may see, if he
oks closely, the tiny file scratch on the
ass at 80, "a and 96 degree marks-or
mewhere near them, as different makers
e different points.
WILLIAM DRYsDALE