The morning news. [volume] (Savannah, Ga.) 1887-1900, 1892-02-26
LITTLE GLASS TUBES
THAT TILL WHETHER TO WEAR A
CLOAK OR CARRY AFAN.


Freezing Point is Marked by Means
Of Bath IN the Snow-Mechanica
Means Of Graduation.
FROM the Pittsbur0 Dispatch.
The making Of a 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 infinitely accurate instru-
ments designed for scientific uses great care
is taken. and they are kept In stock for
months, sometimes for years, TO be COM
pared 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 system zad within
q few years that the very cheapest ther~
mometer should not vary more than a frac-
ton OF a degree from the correct point
Whether, the. Thermometer is to be
charged with mercury or alcohol; whether
1t is to mounted in frame Of wood, pressed
tin or brass, the process is substantially the
same. Mercury generally is used for scien.
titic Instruments, but most makers prefer
alcohol, because it is much cheaper. The
alcohol is colored red with an aniline dye
which does not fade.
WORK OF THE GLAssBLowERs.
The thermometer maker buys his glass
tubes In long strips from the glass factories.
The glassblower on the premises cuts these
tubes in the proper lengths, and with his
gas jet and blow-pipe makes the bulb on the
lower end. The bulbs are then filed with
colored alcohol, and the tubes stand for
twenty-four hours. On the following day
another workman holds each bulb in turn
over gas jet until the colored fluid, by its
expansion, entirely fills the tube. It then
goes back into the hands of the glassblower.
lie 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 hundreds
of them, perhaps thousands ARE ready. Then
the process Of gauging begins. There 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. So Fair. This is
found by plunging the bulbs into melting
snow, No other Thermometer is needed
here for guide, for melting snow gives in
variably 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 into heecy. snow-like particles,
which answer the purpose as we'll as snow.
GETTING THE FREEZING POINT.
When the bulbs have been long enough
in the melting snow a workman takes them
one by one from their 10y bath, Selling each
one so that bis 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
upon each, now go into the hands Of another
workman, who plunges them, bulb down,
into vessel filed with water, kept con-
stautly at 64o. A standard thermometer
attached to the inside of this vessel shows
that the temperature Of the water is correct.
Another tiny scratch is put at GA.
Then third workman plunges the bulbs
into another vessel of water, kept constantly
at 96e, This is marked like the others, and
the tube is now supplied with these guide
marks, each S2e from the next. A small
tab is then attached to each tube, on which
its number is written, for owing to una
voidable variations in the bore of the tube
each one varies slightly from the other.
With its individuality thus established,
the tube now 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 So,
$40 and $50 marks on the tube. The
frame is given a mum Der corresponding
with the number of the tube, and the tube
is laid away in q rack amid thousands of
others.
MARKING OFF THE DEGREES.
The frame, whether It be wood, tin or
hrasa n bn eyOY1oinnp xzha ;t
is laid upon a steeply-sloping table, exactly
in the position marked for thermometer
of that size. The 32', GA and 96e marks
must correspond with the marks upon the
table; if they do not the error in marking is
instantly detected, and the frame is sent
back for correction.
A long. straight bar of wood or metal ex.
tends diagonally across the table, from the
lower right-hand corner to the upper left
hand corner. On the right this works upon
pivot. and on the left it rests in a rachel,
which lets it ascend or descend only one
notch at time. That notch marks the ex-
act distance of g. With the three
scratches already made for basis the
marker could hardly make a mistake in the
degrees if he tried.
The marks made upon the frame or case
are all made by hand with geometric pen
md 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 to the frame, and
the thermometer is ready for the market
without further testing. Some makers use
only two guide marks, but the best makers
use three.
In the process Of manufacture the ordin-
AIRY thermometer goes through the hands Of
nineteen workmen, half of whom are often
girls or women.
Some Of the larger concerns In and near
New York produce several hundred thou
sand instruments annually, and on every
one of them the purchaser may see, If he
looks closely, the tiny file scratch on the
olass at goo GO and QRo marLa-nr