The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1892-02-14

mon use, and these are made rapidly,
though always carefully. The method of
manufacture has been so systenatized
within n few years that the very cheapest
thermometer should not vary more than a
fraction of q degree from the correct point,
Whether the thermometer is to be charged
with mercury or alcohol; whether it Ii to be
mounted in a frame of wood, pressed tin or
brass, the process is substantially the same.
Mercury is generally used for scientific in
struments. but most makers prefer alcohol,
because it is much cheaper. The alcohol il
colored red with an aniline dye which does
not fade.
The thermometer maker buys his glass
tubes in long strips from the glass fac
tories. The glassblower on the premises
cuts these tubes to the proper lengths, and
with his gas jet and a blow pipe makes the
bull on tho lower enc. The bulbs are then
fllea wiNh colored alcohol, and the tubes
stand for swenty-four hours.
On the following day another workman
holds each bulb in turn over a gas Jet until
the colored fluid by Its expansion entirely
fills the tube. It then goes back into the
hands of the glassblower. He closes the
upper end, and turns the tip backward to
make the little glass nook which will help
keep the tube in place in the frame.
The tn bes now rest until some hundreds
ofthem, perhaps thousands, are ready. Then
the process of gauRing begins. There are
no marks whatever upon the tube, nothing
to sho the temperature of the atmosphere.
and the first guide mark to be made is the
freezing point, thirty-two degrees Fahren-
heit. This is found by ~plungina tho
bulbs into melting snow. No other Their
mometer ia needed here for q guide. for
melting snow gives invariably the exacs
freezing point. This is an untailing tes:
far NM k~borrnnmnkar whpap nCcurarv !,
be suspected. But melting snow 10 not
| alwayst to be had, and a little machine re-
sembling a sausage grinder ia brought into
use. This machine shaves a block of ice
into fleecy, snow-like particles, which an
swer the purpose as we'll as snow.
When the bulbs have been long enough
in the melting snow a workman takes them
one by one from their icy bath, Selling
each so that his thumb nail marks the
exact spot to which tho fluid has fallen.
Here he makes a scarcely perceptible mark
upon the glass with a fine file, and goes on
to the next.
The tubes, with the freezing point mark
| ed upon each. now go into the hands of
another workman. who plunRes them, bulb
down, into IL vessel filed with water kept
constantly at sixty,four degrees. A standard
thermometer attached to the inside of this
| vessel shows that the temperature of the
water is correct. Another tiny file. scratch
is put at si1ty-four.
Then a third workman plunRes the bulbs
into another vessel OF water, kept con-
the others, AND the tube is now supplied
with these guide marks. each thirty-two
degrees from the next. A small tab is then
attached to each tube, on which its number
il written-for owing to unavoidable var
iations in the bore of the tube each one
varies slightly from the others.
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 OF the frame, corresponding to
thirty-two, sixty-four and ninety-six de-
gree marks ON the tube. The frame ID
given q number corresponding with the
number of the tube, and the tube ia laid
away in q rack amid thousands Of others.
The frame, whether it be wood, tin or
brass, goes to the gauging loom, where it ia
laid upon a steeply-sloping table. exactly
of that size. The thirty-two, sixty-four
and ninety-six degree marks must corres-
pond with the marks upon the table; if they
do not the error i'll marking ID INSTANTLY
detected, and the frame is sent back for
correction.
A long, straight bar of wood or metal
extends dlagonally across the table, from
the lower right hand corner to the upper
left hund corner. On the right this works
upon u rivot, and on the left it rests in a
rachel, WnlCl ietk ~ aSOenU 1nu uoEOeuu
only one notch at a time. That notch
marks the exact distance of two degrees.
With the three scratches already made for
a basis the marker could hardly make u
mistake in the degrees if he tried.
The marks made upon the frame or case
arc all made by hand with a geometric pom
aud India ink if the frame is of wood, md
with steel dies if it is of metal.
The tub bearing the corresponding num-
Der is next attached to tho frame, and tho
Thermometer is ready for the market with.
out further testing. Some makers use only
two guide marks but the best makers use
three.
In the process of manufacture the ordi-
nary Thermometer goes through the hands
of nineteen workmen. half of whom are
often girls and women.
Some of the larger concerns i'll and near
New York produce several hundred thous-
ind Instruments annually, and on every ono
of them the purchaser may see, il he looks
closely, the tiny file scratch on the glass at
thirty-two, sixty-four and ninety-six degree
marks-or somewhere near them, ~ differ
ent makers use different points.
WM. D~RyspALE.
Copyright,
s..--a----~---s ---+---~re-r=- Il.
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liz the most exquisite preparation In the
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