, 1869-08-04


! mo line :, O D, ictt!ng the lower part
aans, pe,pend,culany. wtfle the upper part leaas
, HaEk about kkh1sctquarFT9c VI tho 9ng1c towards
{ Tie hor1non- trPressnta ths South Pole; inc
North Ppte, and a cturesponds 10. lfse posstoa,
bf the earlha eTuafer. 1Ee suns dccifnation 10
.tug16 degrees II mtnu' Is and b, seconds north,
Tho sun VIII be vertical II noon IA that uumber
-osAezrrr1 Rpd mtuut1a Of north latitude Tho
moon I Aecsauztnu being Ii 'tegreett AK nin-
i ues,. T. zfeafeF thai tnat;; Of the san, snd she
th4 1efoto les north ot Tbs line Joining tarentzsa
~ lha eanh And san. and for tco' sauso
rcsssau bor sba&6w rsHB lMther north than tho
vertical line, ,xhI]d the apex teachts beyoal tho
.ea1thH A1rtaee, giving: considerable breadth
i, who're ksd1kcs tho ground The shsqcw sa-
.yanees tean3 townnts lhe Spectator, oecanse tne
moon moves faster thepthe san in that direction
AMONG tn4 nxtd stara, battosh The run and moca
appear to ora tn ttc' opposstc direction tTe>f-
warl1, btu.ase sne exltn*1 mctlon On her axis IN.
a. u from A ton asrds the esss-
: The reader mar q1asp TIE pneoonc4oa Hifh
tplezalld e1hctnesAN he fan consider himself a
,atxn1tng near tho san It thu utne u sne echFzes
and Ahte from thAS poaltton TO- watch the COM
pound molton al the Garth ami huE aatellte- He
would sec both bodIes u nearir circular, because
tnes Illuminated kuztacea would ha taEned direct
;ly roHards him. The moon'a appaseus diameter
would Ne 1irtie more than one-fourEn cf that OF
ito earth. The moon would pass ;ae1oas the
latgcr body, and heF shadow would s7eep AHoas
tht ea1th1 surface like baack fntch; ~a1lc the
earth would be seen to rotate on hcTfcwn KE6 tn
t1e same dire ton "a the shadow was moving.
The motion Of The shadow would be something Ike
that Of the rloud-shadoT1 sometimes seen cutting
I along, bat much more rapid than they. Tha
reader tna5 now mentally resume hts position On
the ca1th's surface and consider that As the point
Of obse1y attou. 81
When at the time Of m eclipse, tho apex Of the
ahadow reaches iarther than thu carth's surfaer.
the eclipse ia total, because the observer, being
within the shadow, the apparent diameter Of the
noou Is grenttE than that Of the sun, and CON-
pleteiy hides II from Eiew. When the iuElinares
arc both nearly At thcr lacau tayesage) dtst2ncea
from the earth. their apparent dtnmetet1 aro
equal, and tho ape1 Of tho shadow jost touch Is
the 1urface reducing the limit Of the total eclipse
to mere. line. T.. II tae conlcal shador
bc shorter than the average.
tho spex does not reach the
surface. and to m observer In The linc Of the
shadow The sppaYeus Mnnaater Of the moon Is less
than that Of tho SUI. In this caAs, Hhcn the
nea OF The 1untnarks arc In the sa1ue line With the
eye Of the observer, the suns edge seen shining
out all aronud the moon for soue seconds. tic
breadth Of TIC luminous ring being greater IN pro-
portion to the ahottueAa Of the shadow, When
j tha shadow u 1ne ahostest possiblc, only ssAol1
niles long, the apparent brealta Of this E.uz A
! minute eis scaonds q arc. THIS phenomenon
SCALED an "annnlaf" eclipse, from Sba I1ua
word unnt1ss-aE1nE.
An observer on the ea1th's surface, AnyHhezc
within the track Of the shadow, VIII sac tbs sun
entirely covered By tne NEON, or the moon entire
u surrounded By tho suu, according as the shadow
:rsaches the eye or falls short Of II II the OBJ
;serrtr BE some distance outside tae path Of the
shadow, he wll then sse the mooa pass over .
PORTION Of tho su1,a disc, and the eclipse wilt up.
pear to him to he but PARTIAL u IN the case Of
Chicago, the gtcatest ohseuration for which place
On Saturday ne1t, Is shown IN the second diagram,
and The nnobscured portion Will be, greater III
proportion ii the distances Of til q obsetEa1 from
the shadow lncreasas The reason Of this will be
apparent r. NC remember that, the sun
.s about 800 tt1nea farther oil than
the r. n,ooD. Let us suppose two
objects Of such size as that, whcn one Is placed
aJard distant from the eyc, and the other sal
yards heyoEd the nearest object shall seom 10 lust
eoret.thn farthest- II, now, the eye be. lifted.
few inches, the difference - distance Will cause
Ee!-tiyc lowering OF the 1ealrst object anH *
posc tie upper portion! of the most ustart one.
similarly, II the point Of eight be depressed, the
,lower portion OF the most distant object will snow
cut under that which Is nearer. Hence, when ihc
observer Is south at the total limit, the mouo OBJ
scutea only part Of the sQn ! northern. side, aud
tho contrary. The Total with Of the band Of ter
rtory Included within the limits OF tho pat-
tial eclipse lis yeH variable. We may tult'
cata Its average Hagnltude h5 gi'ins It's
dimensions on the line 1unulng through Chicago
In the present tnstance. The angular value Of the
hall breadth Is cqua, to the sum Of the apparent
sCmdlarlctcra Of the sun and noon-equal to 81
minutes 81 seconds oi arc, nearly. The llstlnce
OF the centres Of the earth: and moon t8 32a 80
miles At the instant Of greatest ,obscurAtlou
1T Chicago. which gives a,12A2' miles 81 the half
width, measured through tho ca1th.s ceutre, per-
frffN n thR n nj IN
ern limit extends q degrees Ak mioutes 1FouA
tho central ltue- or l,oe22s miles as measured on
tho eaIth's surface. The noflhern limit c1tents
2cs69 miles, 20 that the partial eclipse ls visible
10 distance Of rbout 1s4 degrees On the other
side Of the North Pole. -
Na now SEQ the Ioe and rht Of tetal cc.tpEe
Of tho SUD- The next consideration Is aA,'l.
Eellpses seem toocctr with provoking irregular
tty. though there Is u new moon every month
II VIC suppose au orange Travelling around Tho
track OF circular tace course, once ear. with
large glass globe near tho centre Of the nchl, aud
. powerful light In The globe, We hhal have fa!r
representation Of tho movement Of the earth
round tho sum- Suppose, now, that large barrel
hoop 10 lnli on tho lEk, with the orange as the
centre Of tue circle, aud that u marble bc lnads
10 move along the circumference of
tho huGp once cnch mouth We have ftir
relative orbit Of The nsoop- Every time
that the mafhlo ccmca between the
orangu and the globe, It represents the ptaAo af
new Muop, and aigo TINT Of she Eo!ar eclipse, tte
calsc oil .hreu i,oIies being tho aae nai rlano
af tho raco-s.aek. the light frum tho globe woilIl
cauks tho shadow at tho n1A1hie to fAu upon tho
orauRp. But tho moon oEttt u not On tho aame
plane with thAl OF tho earth. An to represent fts
reativs poattton accurately. NC must suppose one
slos Of the hoop 10 b lifted avo or slx f1chcs
shore the level Of ths track and tho oppoatp nIts
10 ba depressed eoncspondln9y, while tho aoop
uscl also reyolses in such sneuncr ~ that tho
Two oppostte p0inis WheTo It cuts The track tho
noass, viii uaaxs eos couap,cts revolution In
about lsN JcarS. q. "
Cnaer th,a coadl,ion oi talnft, the shadow Of
thc mssaln would fail Aboss tito plano ~ tne racA
ntet turing anA hatt Of tho mouth, and btIow II
Outing tho othss halt, II II aiso svidsnt taas he
shadow could ouly 4Al On tic .ornu9e NJ sh6so
tlug& whom tha ruxontasa nl Tho 'L'ts hai broo9tt
ono Of thoae Inn potnt1 Of tntsnecslon tttwoen
shs Rlo1s and sheotaugs u ths raus ti4a that
The Eo1olastou VI tha nasn!s aai brought Ii round
10 tho Aato posls!on. a.
!, III cshry words, ito moons shallow, At tho tine
ot now moon. falls notth ot tqush ot lho catth,
unltsa, At tho 1&snu tlmf, uno Ut tho ho4lcs bo
within " tlexsrca ot straight 'tna fro tho saFsh
to tho aln. II tho ntAie be c1kcJY On tho xat.tt
Hno, then tho nh AddN will poss scsosA Tho ca{th la
such way Al 10 dtyide 4 into TWO equal hAlso..
II tho uuun he net Ia this node. hut at'!l within
tho AnlsA pt u degrees tron II, tho shadow VII!
pa1s iSErRuiariy on ono side. Thus, IN tito eclipse
Of saturday ne1t the mooa Will 10 little dlataueo
north Of tho line Joining the ccntrus Of tho carth
and i'm; hence tho shadow will fall north Of .
lhas. line, and pasA within % degrees Ut tho
North Fole.
TnA 1rlau7o poa!tlon Of the moon aud nodes can
cccur not leaa than tNlce, nor moro than asa
times, IN any one year. The ayrsaRc number Is
shout nine In four yaasa OF Il In 4a1 lunAt1ons.
In the couste Of th!s period ls years II daJal tho
earth and noon and nodes have returned 20
nearly to the Ra1uc relative positions that the
node u within . minutes and II sceon41s Of the
original place, antat tn1t Interval, therefore. We
md regular return a she aa1ne pf1er Of ecltpscs
for many hHcs. Tins the eclipse OF aasusdaT
next win return III 1s years, II days, hours,
minutes aud s.es3 seconds Afterwards, II Leap
Jear b Included only four ttmes;And Ia IL
3ears, 10 d1yS !kc, Il Leap year Is Included i've
times; that Is, about O'Clock tCnteago tine} IN
The morning Of the 18th Of August, 1851.
1t Is manifest that tho nc1t return Of this
eclipse, though yik,bia In about TIE tamo Latitude
"a this year will mt be xeen In Chlcazo, uDr IN tho
Tnlted States, the Aun and moon being uader tue
e41th It ths time, We sec. theus that though hy
forwards or backwards, for auJ number Of JcArsto
md the recurrence Of m ec'ipse, the return will
not 10 70 the ypot Of The eartna surface. In
deed. tho application at ths cycle caanoE be de-
pended on Tor tins, NJ the motion OF the moon ta
exceedingly tKcRnlAT,s and may vasJ the time an
hour or moEt from that found by sha xTcfage tn
tr1l The approximate datR Of future eclipse
maJ, however, be Ioond by means Of this ttmple
tormuta, knowing the date ot I'll
the eclipsaa which hAFa occurred. during
paa. cycls Of 9ss lanastons. The t1ue places Of
The sun md MOON must then be computed Tor sev-
era1 hours before and alter this mean, OF oyersGe
tire and ffhe prpcf infant Of conjunction. a.