Copiah signal. (Hazlehurst, Miss.) 1888-1899, 1888-02-09
ABOUT BARoMErgaa
IN. Prinstpie. Iasoivea tn the ch@n9~s
shlsh the asr-sry Unaerge.s.

shlsh the asF-ary Uaasrgs.a
The Fundamental principle u the
construction - the barometer u best
showp In the experiment which led
Turricelli to ib- aist discovery ~ the
presence q the air A Elas-t tube about
thirtl three 'prbes long. opened si one
end. j. completely hlled With mercury.
and being FIRMLY closed by the thumb.
j. inverted aud plaesl vertically In
cup containing mcrcury. When the
thumb i. removed the mercury siuks In
the tab" an u stands, generally. about
thirty inches alsp,s the level u the
mcreury in the cup. leaving In the up
per part n space free ~ air which re-
ceircs the name ~ ,he Torrieellian
Vacuum The mercury within tha
tube being le-. removed from the pres
sure - the air. while lhn' IN the cup Is
exposed 81 II. the eolumn falls On the
pressure AZ the section "a the hole, In
the sams plane as the surface n the
msreary in the cup. is the same within
ard without thu tube. We have yet no
better index n the pressure II the at
mo.phcre than the simple mercurial
culupn % Torrleelli aud In all ssast
observations ID is taken a. the only re.
liable standard simple a. the baron.
rter H. its construction demands con
siderable care aud experience. IL j. of
ths first Importance that the mercury
- - used y chemically pure, other
y j." lis auidiiv = impaired aud the In
side ~ the tu,s bccumrs coated with
iupuH7''es be such way -
to u,Hdef susrstt observations I'm
possible Mercury. a. usually sul.
!. not pure; aud before being en-
ploysd frr btramster., must BE- shakes
veil with h. .ghly diluted bat pure nitric
arid. o. femoye extrane0us metals and
oxides H. hlling the tub" il i essea-
tall, pa.~..af, g. get tha column free
from air aud moi.ture To effect this
the mercury. after flling 3. boiled In
the tui.r a., that air and moisture may
b. eSpelI,d Btrom,tsrs Are usually
divided intotgO elas-r. -elsiefn hsaToH'-
rter aud ,iphon barom~ter The siphoa
barometer j. ia msny respects more
perfect instrument than Va" cisi"rn.
The wheel barometer. originally IA
,cntcd ~ Hook Bad generally seen
~ = paflas ornamout. ha~ litile - rec
omsa.nd ID "a l4#s.-i s.szTsfy tnstru-
msn1 Ihe u>o. q IA. bsruWetsr may
Le cla..ih.ai iaip physical. hyIsomet'
ricsl asd meteorological i, is oi 80
sruiial u-e be- al IN, sical researches
here the mechanical, optical acou~-
ural aul rhsmis1l properties ~ air or
other ga.es are deiandsut "n the pres
sure IT the atmosphere lie uses in
h,psometry. ur the art - measuring
the height. Il mountains. i very val
able. bat the h,.st knowu use ~ the
harumrtsr G. a. meteorological instru-
ni.ni. or ~ weathrr glass Opticians
have attached o. certain heights ~
the barometer certain states ~ th"
weather and II rcrtslu points ~
the saale the wauls Rain, e Change
.Ll-.v E..ss, ss,-tr.. str utsrs-sit ssas sass
rousrstipu taus iusftu'sl &. very mis-
l.sdinu fha.e Nh have observed
niB.t e s,fully thu connection Il
barometer, hsi gl,ts y 10 chaugss u the
weather. disr,ga 4 entrrlt the use of
these letnis tud state that IL u not the
actual height IT To- barometer at any
Place. bat lhi. height q. r"HiParrd with
~, II surrounding regions. which In
dicatrs ln. trh'ng weathrr General
ly speaking falling barometer ina'-
catss rain. = rising barometer iair
weather A steady barometer foretelis
q continuance q the weather n the
time when low this i generally broken
~ bad. anil whom high. fair 4 sud
Hrr fall usually precceds a storm. the
violence oi Ah,,h - ia prop"riion 10
N. haromrtrie gradient An unsteady
htlomrtrr shows an unsettled state ~
ih, -e#tier, gradual changes, the AZ
praarh q .om, n",ili'nsnt condition ~
a. rhr variations must also be inter.
prrtcd vith reference 10 the prevailing
winds each diflsrent wind having some
peculiar rule. The connection be-
tween tho change. n weather and the
pressure a The atmosphere i hv no
means we'll understood. Toledo Haie