Iowa voter. [volume] (Knoxville, Iowa) 1867-1874, 1870-11-24
THE THERMOMETER.
by s. II. PEABoBY, NJ. A.


ANYBODY knows what thermometer
is 1t is glass tube with bulb at tho
bottom it has mercury In 1t, and hangs
fastened to tin scale behind the door.
People look at it when it is very hot or
very cold, to see how much it will do "a
fret. That's the common idea. Let us bo
more precise. There ia glass bulb, filled
| usually with mercury, sometimes with
colored alcohol and, in fact, any liquid
would serve in some degree.
| Increased heat causes the liquid in the
bulb to expand, and the increased bulk
must find room for itself in the very fine
| bore of the tube attached This bore seems
| to have considerable breadth, when viewed
in one direction, but If seen from the side
is found to be exceedingly thin.
How is thermometer mades First, \
glass blower takes some melted glass on
the end of an iron tube, and upon one side
he adds small amount of opaque white
glass, also melted He blows into the soft,
adhesive mass, the air forcing hollow
space in the centre.
When the glass is long bottle with
| thick walls, another workman scizes tho
! bottom with pinchers, and then the two 60
quickly in opposite ways pulling the soft
substance out into tube the hole within
and the walls diminish in the same pro-
portion, SO that the tube may be very fine
without closing The patch Of Opaque
white glass has also drawn out into u
white strip, against which the mercury
may be more clearly seen Although tho
tsbe may be as much rs twenty or thirty
feet long, only small piece from the mid
| die is lust suited for thermometer tube.
The rest, if not used for other purposes. Is
| broken up and melted again.
/ A workman selects piece OF proper
! length, and heats one end in the flame OF a
/ lamp until the glass melts and closes then.
/ by blowing in the open end, and carefully
! turning the glass in the flame he forms the
/ bulb upon the closed end. This requires
| great skill, which is obtained only by
/ much practice.
The open end of the tube Is placed in
dish of mercury while the bulb is still hot.
/ You understand at once that If the glass is
I hot the air within is also hot, and there
\ fore rare. As the bulb cools, the air con-
denses, and then the pressure upon the
surface of the mercury In the dish forces
/ the mercury up through the fine tube into
/ the bulb When the tube has sucked up
| all il cam IL il inverted again, and held
/ over lamp until the mercury boils; tho
vapor drives out the remaining air, tho
open end is sealed in the flame, and the
| thermometer is made.
Now IL must be fastened to a plate Of
metal, or something equivalent, on which
! is scale Of some kind.
! First, the tube IL set into water that con-
tains melted ice and after standing awhile,
the place of the mercury is marked rs the
freezing point. Then 1t Is placed in boil
ing water, and the place OF the boiling
point is found The space between these
two points may be divided into as. many
parts as we choose, and each may be
called degree If we only understand
each other
Fahrenheit, Hollander, In 1909, divided
the space into 1872 parts, calling the frccz-
ing point }2 and the boiling point 212 his
scale is used In Holland, England and
America to this day. Celsius, a Swedc,
divided the space into 100 parts, and Reau-
muir, "a Frenchman, into eighty parts. Both
Celsius and Rcaumur called the freezing
point 0. Occasionally large thermometers
have all the three scales upon the same
plate, 50 that the observer may use what
he pleases. ;,
So then, when the thermometer indi-
Gates 102 degrees by Fahrenhcit's scale,
the mercury has passed over 70-ie0ths Of
the space from the freezing to the BOILING
point.
The size of the degrees between 30 de-
grees and zig degrees Is continued above
and below The graduation In mcrcurial
thermometer may be carried no higher
than $50, since mercury boils at that point;
nor more than 30 degrees below 0, since
mercury freezes there. Thermometers
which Indicate greater cold arc filled with
alcohol or ethcr.-Littls Chtef.