Natchitoches populist., 1898-05-06


Teacher-Stand up, Johnny, and tel
the class what is thermometer.
Johnny-A 6e 6ermometer lis. an in
strument for SHOWING. how bot 1t is.
Teacheh HS is thermometel
usually made. &hd how d6es it oper
ate?
Johnny-There is a glass tube witt
mercury In it. and'a bulb at the bottom
opening into the tube. The bulb |;
full of mercury. The tube is only
partly full Of mercury, and there is nc
air in the tube. or bulb, both being
closed. The tube is placed close to a
scale or index, marked with figures, the
big figures at the top When the
weather is hot mercury swelis, 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
1t swells 1T must rise in the tube. So
when 1t is hot the top of the mercury
is opposite big figure, and when 1t is
cold the top of the mercury is opposite
a small figure on the.scale..
Teacher-Very well 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, siri but ] don't quite
understand how it would work. Will
you please explain 1t to us?
Teacher-I will do so, Johnny, for I
wish the. class to understand the ne
cessfty of using every instrument
carefully. and to show you how an in
strument may deceive You II 1t is out
Of order, or has been tampered 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 ii, will always reach
at the boiling point Ct 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 sbrinks and goes down in
the tube; 50 that IFS top is at zero, and
1t 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
viii rise and fall
Having found the distance between
the freezing and boiling points OF
water, this distance is divided into 2l2
equal parts according to the Fahren-
heit scale or 400 parts according TO the
centigrade scale, and these distances
or degrees are marked on card or
plate, which is carefully attached to
the glass gtpbe, SO that the zero point
on the tube and on the scale shall be
exactly opposite.
Sou can readily understand that II
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 trl,e temperature.
SO II you change the scale, by applying
a centigrade scale instead Of a Fahren-
heit scale, while the zero may be the
same, the degree Of temperature indi-
Gated byjAe top of the mercury will be
quite tiifnsfsnt ON THE two scales. or If
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
hing on the scale.
4 Now, i wish the class to apply the
same reasoning to another matter.
rhis country at one time incurred a
great debt, called the national debt.
rha height Of this debt was marked
III scale. indicating dollars. not de-
,rees. These dollars we're on what is
,alIed the binetallic scale, and were
ach worth at that time less than one
,ushel OF wheat, or less than Ave
'ounds of cotton The highest point
cached on the scale OF debt was about
2 200. GOO 900. After the people of the
United States had been working very
ard to bring down this debt, it is pro-
osed to substitute different scale or
ndex, called i monometallic or gold ),
Eandard scale. Some say this change
I standard has actually been made.
he dollars or degrees on this scale
rs very different from the dollars or
egrees on the bimetallic scale, being ,
scYl worth about two bushels Of wheat !
+ ten pounds of cottorll This new in ,
ex shows the top of the debt to be at /
bout the game mark as on the himetal-
6 scale, but some people are begin ,
ing to see that It will take twice as