Wichita daily eagle. [volume] (Wichita, Kan.) 1884-1886, 1885-08-29
THERMOMETERS.
HOW THEY ARE MADE AND HOW
rHeV ARE TESTED.
Uniformity Of Bore Essenttal-SAapo end
Size OF the Bubble Grad uatiea
o. The Scale Seien-
fife Task.
iCl,icaso HeraIil

tti5caSo ifefaiAl
Tee standard thermometer il . combins
ton OF practical science sud requisite work
manship and for 4 irst-class instrument
you have TO pay as many dollars a. you pay
cents for the ordinary article. and then you
can't swear By il, because there arc so many
influences that infect the CORRECTNESS Of the
thermal register. not to speak Of the inlu.
encss upon the completed instrument by the
! location Of the latter.
Numerous precautions arc required to
turn out standard instrument First Of
/ all comes the choice Of tube The bore
has 70 be carefully tested to see whether it
is Of uniform capacity. In mot Of the tubes
the bore is wider On one end than on the
other. although the difference may be %
small that it requires very delicate opera
lions to es:a bl;sh il Quite frequently lie a
hunirel pounds Of the small tubes not more
than half n dozon are found which are Also
luteiy trus, because from the very nature of
the case the bore. being produced BY blow
ing, Is in fact nothing else than Q portion Of
very elongated cone. After the tube has
becp ,electei the bulb is fixed by melting
one end Of the tube in tho flame Of an
alcohol lamp AMI blowing in at the other
Then small quantity Of mercury is admit
ted By alternately cooling and beating
the bulb the very delicate thread Of the
huii is driven from one end Of the tube to
the other. and during this process its length
is carefully measured in all parts. Should
the lsngth alter in various situations the
workman knows that the capacity Of tbs
bore is not uniform.
To make the bulb Of the required sire il
solely a matter Of practice, as no machinery
has been invented to producs it automatic
ally. II the bulb is too large the instrument
will register very slow, and il it is too small
it will not contain sufficient mercury to reg
ister very high temperature. The shape Of
the bulb is also of Importance The spheri-
cal shape is considered best adapted to re-
sist the varying pressure Of the atmosphere,
while cylindrical b .lb' expose larger sur
faces of mercury. and are therefore pre-
ferrsd for more delicate instruments Very
small AMI thin bulbs for small quantities OF
mercury have been made. but the indicating
column mu' necessarily be 50 fine as to Be
useless for practical purposes. Spiral or
coiled tubular bulbs were made SO as to oh.
tain greater and mora oven distribution OF
surface exposel 70 tho atmosphere, but
these bulbs require such thickness Of glass
that the effect sought to DO obtained is ire.
Quently nullified-
SHAPE and sixs of bulb and tube having
been determined, the filling is done in a very
ingenious manner. and alike for both mer-
curry and alcohol as thermal registers The
bulb is heated while the open end Of the
tuba Is limbo ldel in the fluid, say mercury.
Upon allowing the bulb to cool the atmo-
speric pre- Ssurs drives some OF the mercury
into the tube. and this process Is continued
until there is sufficient mercury In bulb and
tube. 1t is Of the greatest importance that
inc mercury Do Tree from moisture and air.
ana % accomplish this tbs metal Is boiled
ne.ore the hiiins process. After tho filling
" Is Doiied again In the tube, and when the
explosion OF ar and moisture Is complete
tne workman generously closes the tube by |
tne name from his biowpipe.
mat nnsne' the purely mechanical part
OF making the Thermometer, for the gradua- !
uon OF tine scale may truly DO termed Sci |
enuhc proceeding, at least SO far as gradual
ing stan1 ard instrument is concern.d. In |
the common thermometer the tube Is fixed |
70 scale on which the degrses are marked, |
wniie IN the standard instrument the Gale Is |
engraved IN the stem ITSELF In order to In |
sure tne greatest possible accuracy OF obser- |
sation- ms exact freezing point has TO b |
oeIer ihihed hrs'' anu TINS IS Done by means |
OF me!ting Ice, which mas always the sans |
temperature pr"'i1e1 tho water from
"n,cn tne ice congeaied Is pure The bulb
anu ',,e lower PORTION oi 1hs tuoe are piaced
III neilihg ICE ana where the mercury Is
s.a,iohary inc ireezns point Is marked
LUIS - comparatively easy matter but tc
, NC n'ie 'he oo'iins POINT Is more dimcult
oecouse IL varies WIKI tne pre- sure OK the
h',Iospnere-
Ohuer certain coalition', combining GER