Kansas agitator. [volume] (Garnett, Kan.) 1890-1905, 1898-04-01

the class what is thermometer.
Johnny-A thermometer is an in
strument for showing how hot it is.
Teacher-How is thermometer
usually made, and how does it oper-
ate?
mercury in it, and bulb at the bottom
opening into the tube. The bulb is
full Of mercury. The tube is only
partly full of mercury, and there is no
air in the tube or bulb both being
closed. The tube is placed close to
scale or index, marked with figures, the
big figures at the top. When the
weather Is hot mercury swells, and the
mercury in the bulb and tube ex-
pands. AS the tube is closed the mer-
curry has no other place to go, and as
it swehs 1t must rise in the tube. So
when it is hot the top Of the mercury
is opposite big figure, and when 1t is
cold the top of the mercury is opposite
small figure on the scale.
Teacher-Very we'll stated, Johnny.
Now, suppose some one should slip
the scale down without moving the
tube; would the top of the mercury
still indicate the temperature?
JOHNNY think the thermometer
would be wrong, sir; but I don't quite
understand how it would work. Will
you please explain it to us?
Teacher will do so, Johnny, for
wish the class to understand the ne
cessity of using every instrument
carefully, and to show you how an in
strument may deceive you if 1t Is out
of order, or has been tempered with.
The standard thermometer is made
very carefully, about as Johnny has
described. The tube must be of exact
ly the same internal diameter through
out its length. The tube Is carefully
sealed when the mercury is put in and
the air has, been exhausted. The bulb
is plunged in boiling water. and as
boiling water is always 212 degrees
Fahrenheit, the mercury rises in the
tube to the place it will always reach
at the boiling point of water, and the
place is marked on the tube. The bulb
is then plunged into mixture of salt
and ice, which was once supposed to
be the coolest thing in the world and
the mercury shrinks and goes down in
the tube, so that its top is at zero, and
it will always go to this place when
the bulb is in this mixture or in place
equally cold. Thus the two extremi-
ties are marked, to which the mercury
will rise and fall.
Having found the distance between
the freezing and boiling points Of
water, this distance is divided into PIP
equal parts according to the Fahren-
heit scale or 100 parts according to the
centigrade scale, and these distances
or degrees are marked on a card or
plate, which is carefully attached to
the glass tube, so that the zero point
on the tube and on the scale shall be
exactly opposite.
You can readily understand that If
the scale moves up or down, so that
the zero on the scale is not at the
proper zero on the tube, the thermom-
eter will not tell the true temperature.
So II you change the scale, by applying
centigrade scale instead Of Fahren-
heit scale, while the zero may be the
same, the degree Of temperature indi
Gated by the top of the mercury will be
quite different on the two scales, or il
the top figure corresponds the zero will
be wrong.
II the scale were printed on rubber
or other elastic material, which can be
stretched by stretching the scale or
index the mercury in the tube can be
made to appear to indicate almost any
thing on the scale.
Now. 1 wish the class to apply the
same reasoning to another matter.
This country at one time incurred a
great debt, called the national debt.
The height Of this debt was marked
on a scale, indicating dollars, not de-
grees. These dollars were on what is
called the bimetallic scale, and were
each worth at that time less than one
bushel Of wheat, or less than five
pounds of cotton. The highest point
reached ON the scale Of debt was about
81, 700 100000. After the people of the
United States had been working very
hard to bring down this debt, it is pro-
posed to substitute different scale or
index, called a monometallic or gold
standard scale. Some say this change
of standard has actually been made.
The dollars or degrees on this scale
are very different from the dollars or
degrees on the bimetallic scale, being
each worth about two bushels of wheat
or ten pounds Of cotton. This new in
dex shows the top Of the debt to be at
about the same mark as on the bimetal-
lie scale, but some people are begin
ming to see that 1t will take twice as
much work to bring down the debt to
zero by the new scale as by the old
scale, and they fear they may never
be able to accomplish it.
Johnny-Please, sir, why don't the
people have the same scale they used