The Mitchell capital. (Mitchell, Dakota [S.D.]) 1879-1918, 1909-01-14

government temperature must be add
ed to Or taken from in order to get
the temperature in the street, he is
able to use the unknown amount that
is to be added or subtracted as a shield
and a Justification of his own emo
tlonal weather meter.
1t is not very much of q secret that
the thermometer makers are aware of
The popularity Of the exaggerated
thermometer. and cater to the UNI
healthy appetite Tor sensational tenn
p%eratures. But the making of a scien-
ute Thermometer is a far different OPP
Grafton. 1t takes a sure enough high
brow an ong glass blowers to make a
sure enough scientific thermometer. In
the first place the thermometer is a
thermometer because mercury expands
under heat seven times as much as
glass expands. The mercury used for
the really serious minded machine is
first purified by filtration through
leather under pressure. subsequently
1t is distilled and gets a chemical bath.
Before it is put in the glass it is boiled.
This is not done on the theory that
as the burned child breads the fire so
The mercury, having once been boiled,
will always try to scramble up the
tube every time it feels heat on the
blub. 1t is done to get the moisture
and h air out of the mercury.
at the same time hat the mercury
is having its hot bath the glass tube
is prepared for it by washing internally
ether. 1t is then dried by ex%hausting
the air from it while 1t is hot and fill
ing it With air that has been dried.
When everything is nice and tidy and
ready for the mercury to move in, the
bulb Of the glass is heated. which
causes the air in 1t to expand and boil
over. Then the end of the tube is put
in the mercury and as the air cools a
vacuum is created. and the mercury
sucked in. This Is repeated till the
bulb is filled. The instrument is then
heated to q temperature above that
TO which 1t is to be exposed in use
and, While the mercury is running over
the end OF the tube is wrung off. like a
chickens neck. and the end sealed with
q blow pipe. In fine thermometers n
pear shaped bulb Is left at the top to
keep the mercury from breaking the
glass when under the excitement Of he
hottest day in II years.
Marking Important Detail.
The marking of the new thermometer
Is an important matter. First the boil
ing point is found. This is lone by
holding the instrument in the steam OF
water boiling freely under the baro-
metric pressure producted by Il column
of pure ice cold mercury 16O milli-
meters high at sea level in latitude As
N%S ~ u III Ills ~ VIII pt ScGIl WllGl
a touchy, pampered thing a scientific
high class thermometer is. If the
slightest thing comes up that il doesn't
like. it flies to pieces like Il genius and
is never any good afterwards. To get
the freezing point is a comparatively
simple matter. The thermometers feet.
that is, it's bulb, is put in a bath OF
water and fine ice.
When these two points have been
scratched on the tube it would appear
TO be an easy matter to fill in the
requisite number of degrees between
middle class thermometers. but is not
at all the proper thing for the scien-
tific nobility OF Recommendation, be-
cause of the celebration error. This
error is due TO the fact that the glass
blowers cannot get the hole the same
size all up and down. The difference
is small. a mere few hundred-thous-
andth of an inch or n centin1eter OF
something. but 1t requires Il very abb
truse calculation in high toned mathe-
mates TO find ont. The error being.
ascertained. the glass is marked. The
size. because Of the error, though the
human eye would not notice the Diff
eroncc.
Even after all this pampering. the
really high-toned Thermometers is not
expected to behave herself. that is,
10y u IL Sdilc ana sensible manner.
There is to consider the stem error"
which Is due To the fact that the Their
monnettr may be colder at one end than
the other; the barometric pressure on
the bulh, which 'squasl,es" the mer-
cnfHN up into tho stem: tho pressure of
the mercury itself on the mercury down
IN the bulb, which makes the Their
mometer read a nundred-thousanth or
something lower than it should: and
certain, or rather uncertain anomalies
IN the expansion and contraction of
glass.
Movable Zero Points.
This latter consideration is the most
serious. for it strikes at the Character
and reputation of every thermometer
ever made. 1T seems a terrible thing
to say, but there is not a thcrmorueter
IN me country that has not got q NOV
able zero point. 1t does not make a
BIT of difference; no matter how shin,l-
ed the life of the thermometer has
been, what amount of care has been
bestowed ON it's upbringing, it has this
Flemish on it's character. Ever the
chufch thermometers cannot depend on
hiding their zero points twice in the
same place.
Anyone who has had any experience
with zero points will know how, serious
a hin this is. Every effort has been
made to overcome this hereditary faint,
but without avail. In the good, ex-
pensive thermometers, the bulb is made
OF a different glass from that used for
the stem. Either the glass used is
Jena 49, or Jena So" German glass
es. or "verre dur" a French conception.
BY using these grades OF glass the
movable zero Is somewhat penned in
and circnmscribed In it's perambula-
tons. Moreover. like other exuberant
traits that arc due largely to youth,
the wanderlust of the zero point is
gradually overcome as the thermome-
ter gets more mature and responsible.
While it is sowing it's wild pats during
the first two years., the zero point on
a good thermometer will move upward
at the rate of fully .001 degree cent?
grade a month. This righteousness on
the part of the thermometer leads to
some g%rievous trouble in ascertaining
scientific matter of the gravest impor-
lance. After the thermometer has
passed its second yea and is four or
five years old and has got to q point
where 1t has come to see the wicked
ness OF this unseemly levity, it only
breaks over now arr then. and the en-
tire upward tendency of it's zero will
not exceed .0002 degree ccntigrade i'm
a whole year.
The scientists have learned to make
allowances for the Weaknesses of the
thermometer, and work by the "meth-