Wauwatosa news. [volume] (Wauwatosa, Wis.) 1900-1948, 1903-02-14
THERMOMETER MAKING.
How Boiling and treezing Points Are
Found and Degrees Marked.

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 extremely
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
carefully.
Mercury is generally used for scientific
instruments, but most makers prefer al
eohol because it is cheaper. The alcohol
Is cuored 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
iiutd by its expansion entirely fills the
tube. 1t then goes back into the hands
OF the glass blower. He closes the upper
end and turns the tip backward to make
Il little hook, which will help keep the
tube IN placS in the frame.
The tubes rest until some hundreds OF
them, perhaps thousands, are ready.
lhen the process of gauging begins.
There are 10 marks on the tube and
the first guide-mark to be made is the
freezing point, 81 degrees Fahrenheit.
This is found by plunging the bulb into
netting snow. No other thermometer is
needed for guide, for melting snow
glves invariably the exact freezing point
rms Is m unfailing test for any thermn-
meter when accuracy may be suspected
but melting snow is not always to he
had and little machine resembling n
sausage grinder is brought into use.
This machine shaves block of ice into
particles, which answer the purpose as
wen as snow. When the bulbs have
heen long enough in the melting snow a
workman takes them one by one from
their bath, Seizing each 50 that his thnmb
nail marks the exact spot to which the
uuld has fallen. Here he makes a
scarcely percrptible mark upon the glass;
with tine file, aud goes on To the p.,xt.
The tubes, with the freezing point
marked ON each, now 20 into the hands
bulb into a vessel filed with water kept
constantly ut 96 degrees. This Is marked
IKE the others. and the tube is now
supplied with these guidc-marks, each
- degrees from the next.
WIN us lnuifiuuahtN thus established,
the tube goes into the hands of marker,
who hts lis bulb and hook into the frame
1t Is to occupy and makes slight scratches
on the frame corresponding to the
- degrees, O. degrees and 90 degrees
marks on the tube
The frame. whether it be wood. tin or
brass. goes to the guaying room, ' mere
it is laid uron Il steeply sloping table
marked exactly in the position for n
THERMOMETERS of that size.
\ long, straight bar of wood or metal
extends diagonally across the table from
the lower right-hand corner to the upt,nr
lcft-hand. corner. On tine right this rests
upon pivot and on the left it rests in n
rachel, which let's it ascend or descend
only one notch Mt time Each notch
marks the exact distance of two degrees
London Express.