Evening star. [volume] (Washington, D.C.) 1854-1972, 1881-04-25
WEATHER INSTRUMENTS.
How They Make ThermOn, eters and
BarOmetCrS.

WEATHER INSTRUMENTS.
How They Make Thermometers and
BarOmetcrS.
Marked as has been the advancement In
meteorological science during the past few
years, through the invention OF Instruments
and other means, 1t is many centuries since
the world was destitute of all knowledge of
meteorOlOgy and means for obtaining and dis
pensipg the same. Indeed, some OF the more
valuable instruments for measuring and ascer-
tanning the pressure OF temperatures are OF
ancient origin. and probably Will never go out
Of use. Chief among them are the Thermometer
and barometer. Though both are instruments
who knows how they are MADE. and. since a
consideration of the whole range OF meteoro-
logical agencies would require more space than
ep ,o1e D9 anoW S 19r an ordinary newspaper
Two best known indicators of the weather
The thermometer was invented at the b.
ginning OF the seventeenth century, and the
Holland, and SanctoriOus, OF Italy. Previous
to this era 1t may be considered that the best
informed philosophers knew little more of
meteorology than what they derived from some
practical traditional pr0gnosttcs, which had
been recorded by the ancientS. It is supposed
that many OF these originated With the Chal-
deans. and came from them to the Egyptians
by whom they were communicated to the Gre.
cans, ana thus, following the regular course Of
the arts and sciences, were transmitted TO US
Remer was the first to overcome prejudice
against the unequal expansion OF mercury and
to adopt that fluid In the thermometer; and he is
also thought to have devised the instrument
and scale usually attributed to Fahrenheit, of
introduced the instrument throughout Europe
In the first half of the eighteenth cen.
fury, and his name, accordingly, Is oftener
sou o Sltn Inc mel SUI @ As mercury has
very low temperature or boil except at very
hlgn temperature, Its advantages are appa-
rent. In the manufacture OF thermometers
which are designed to be accurate, great care
and precision are required to be exercised
and 1t is because the work Is often tmperfectly
and hurriedly done that there are so many
stores are deiuged with such productions
which are sold az so low price that it becomes
at once apparent that good instrument could
not be matte and sold at that price. The bulk
OF cheap. imperfect thermometers that Hood
the market are manufactured in New York
state, notably in the city of Rochester, where
D0ys and girls are empioyed to do work that
skilled Workmen only can do to nicely. AS
oftentimes the glasses are mounted on hand
some cases or frames. they Sell readily and
bIing fair prices though next to worthless,
people. however, who know the superior value
AN ACCURATE THERMOMETER,
and will not purchase such "a are commonly
local manufacturers or dealers OF reputation
who are to be found In a few OF the large cities.
and who make 1t point to turn out tnstru-
ments superior to those designed for the trade
In years gone by they also manufactured the
instruments for the trade, but, now that the
extensive manufacturers OF cheap goods have
hooGed the markets with their products, a
gradual change has been brought about, and
the bulk OF their business Is transacted with
individuals. corporations and only such dealers
desiring accurate instruments. In Boston there
are two manufacturers OF Inercurlal and spiri
thermometers and 1t Is conceded that they turn
out as accurate instruments as can be found in
the country. One OF them. gentleman In the
prime OF life, has been engaged In the business
here siEce his boyhood, and Is the inventor OF
meteorological instruments and improvements
whose value has been many times demonStra-
TED. Most everybody has noticed that the
glass Of a modern Thermometer is partly com
posed OF enamelIed or white glass; thus en-
aiding one to more easily note the heighth
OF the mercury. For years plain glass alone
occurred to the gentleman alluded to above to
Introduce the eDamelled or white instead. The
first tube OF this kind was made by him in this
city. and since then 1t has become universal
was millions In It," but al the gentleman made
the Improvement simply for bis own immediate
Dement,, and did not realize that 1t would come
into general use, he neglected to have it pat
his grasp. AS nearly everybody knows how
glass Is DloWD, Ii would be useless to describe
how the glass tubing for thermometers is made.
It is sufficient to say that 1t Is blown at the
glass blowers under the supervision OF
trusted employe OF the maker of thermometers,
and comes to the manufacturer In lengths,
sired. The bore OF the tubing, it is commonly
noticed, appears quite large when filled with
mercury This is because the bore is nat. nc
varies IN size. 1t being impossible to secure
the
POINT OF A NzKDLK
1t Is difficult to get tube of uniform calber
throughout its whole interior, and 1t Is neces-
QrC n OF 0f hnra
tube, which is done by celebration, that u.s. by
introducing short column OF mercury and
observing how much length II occupies In the
which. Tor the nicer grades OF thermometers Is
sometimes etched, obtaining the exact meas.
urement. In preparing the capillary glass
desired, and after that Is done the next thing
is to blow bulb On one end OF the tube, which
is done By heating the glass In gas Jet and
blowing In the ordinary manner. This opera
ton, simple as tt seems L.. nevertheless, very
delicate operation, for bit OF moisture In the
bore OF the ture Will be fatal to the accuracy of
the instrument. novice would hardly fail to
dampen the interior Of the tubing: but the ex-
perienced workman blows the air from the
lungs and e1ectS no mucous secrettOnS.
SO susceptible is mercury to moisture that
finger dipped In the metal Will render It unfit
for use In thermometers. On receiving the
usually closes up both ends OF 1t to prevent
moisture from entering. The bulb and Dor
ton Of the tube are filed with mercury by
exhausttng the air In the receptacle. That Is,
the bulb Is heated In fame and the open end
OF tse tube is air ,Ijsa int mercury. When the
neat is withdrawn the air in the bulb con-
tracts and the mercury rises In the TUBE ana
partly dis the bulb. Then the mercury 10 Inc
bulb is boiled, and, as all air Is expelled, the
tube nect ssarily fills completely with the metal
After adjustment to the required height, the
bulb Is again heated TO expand the mercury
sufficiently TO I'll the tube, and the end Is
closed.
Tho Instrument is graduated to the boiling
point OF water and the freezing point OF Ice,
and when each has been ascertained the points
scale the freezing point is designated at 80 deg.
and the boiling point Is designated at 2l2 deg;
In the centigrade The freezing point Ia zero, and
the boiling point 100, and In Reaumur scale the
freezing point Is at zero, and the boiling point
at so deg. The scale last mentioned Is COM
monty employ ed 10 France, and that first named
in this country and Europe. 1t Is universally
conceded by meteorol0g1sts that the cenugrade
scale Is the better of the three, and the belief Ia
that like the metric system. IL WILL nnally be
adopted here. All Thermometers, even those
that can lay claim to accuracy, are not SUB
jected t0the test Of the boring point OF water
and the freezing point OF Ice, unless the scale
extends to those points
THE METHOD OF MANUFACTURE
described Ia that employed In turning out what
is called an original or primary thermometer;
all other instruments are made by comparing
them with the original or primary thermome-
ter, and making the graduattons accordingly.
AS the bore OF hardly two tubes is alike, while
the inequalities are varying, this requires skill
and pnod workmanship In manufactures