, 1874-10-22

Ibo eccunu GIaE4Atu hnuwa tne relhtlya pust-
tio1s Of tho sun. earta, and moon At tho time of
tho eclipse; b1t Wo aro unable to draw 1t to
scale, like the first. II We tako tho circle repre-
senting tho earth as tho standard, tue diameter
of which ia to TINT Of the eattll Ra to nearly
900 600 900. tho s11n should bo represented by
circle III feet In diameter at the distance Of 48Q
fcot; and the moon should bc ID inches from
the earth. retaining tho sizo represented in the
diagram. which represents diameter Of 9,1G1
miles. Tho lines drawn through 2 and H ",
bounding tie cone of tho ahrth's shadow, moot
at MI actual distance Of $4,000 milcB, which cor
responds to distance OF 416 feet on HE draw
Ing. Tho length OF tho shadow Is very nearly
equal to tho san'e diameter.
{sYo note III this connection tint our unit
globo Of hnlt All inch in diameter is no. tnr from
being moan proportional between tho Garth
and tue ultimate atom Tho atom Is certainly
no larger, as compared NTH lalf-inch marble,
than tho marble la "hen compared with tho
whole earth.}
L1o{rr AND SHADE.
The movcment Of the earth in her orbit ia IN
the direction OF ". 10 Il. the enlightened aide
being always next tho Auu. Tho opposite lAlf
Of tho cartll is IN t1arlnesa and the boundary Of
tho dark hemisphere is tho base Of tue concal
shadow, tho umbra. While the moon is moving
through the urnbra, the sunlight ia intercepted
by tho earAl and falls to reach tho moon she
il thon said to DO eeliy9sed
The penun!bra uAntin, r7c'7es almoat) or partial
shadow, il situated between the un16ra and the
llnea ] 4 md II q. 1t IL axidant, from ~ i'll
Bpeotion Of the diagram, that when the moon is
III this position portion Of the sunlight IL inter-
copied by tho Garth; and the psnumbrn gradnal-
~ durknns, from tho outer edges 1t 4 md q,
moon, At q, receives light from noarly The whole
disc Of the ann The middle OF tia lunar disc at
only receives light from one-hnlf OF the Hlr
and the left-hand edge Of the sa,nc disc is only
illuminated by thin alice Of sunlight coming
from IL whlo to the left Of tho line II ", the
sunlight IL altogether shut of, except the scry
small portion which is bent into tho ahalnw By
tlle rofractiyo power Of the earth'B atlnoaphore.
The ponumbtal aifoct MAY be observed on the
earthB hnrfaue. Il We nnse the shadow which =
high bnilliug cAata In tho street, We find 1t Diff
cult to locate tho line whare tue shadow begins.
II tho line OF the building which casts tho shadow
DO 30 loot from tho p)ace on the ground wllero
tho shadow ouds this uncertain tnTTit0ry will ha
nearly linlf foot III width; the OTTER edge being
IN fn sunlight, tho inner edge in fuil shadow,
and the strip betwoon gradually ahades OF from
light to larlneHa II tho tliAthuco DO fsot, tha
width Of tho uncertain ground il about inotl ;
tint being tho proportion which the radius of
ciru}o bears 10 tho angular diameter of tho sun.
Tho average ratio il 1U9 to /.
The direction of tho lnoon>s motion III her
orbit III tho Hama ~ thai Of the earth II IL
Bll0ND by tl1o ari0wB. The uloon entHrH the pe-
nlinlbra at A, thence through the ,,nlbra from
weAt to eAst, aud thon through the eastern edo
1t .s pe.sVual!@ to =. 1tls evident tAat she can
usIly u this when tle dark Hio OF the eartl
! that IL, ut tic limo Ut full moou- Why mt ut
| tile t'sto III eyorY till lnona. giving innar
eclipse At regular intervals Ut swensy-,,ine and i
| lalf daysf
| THE Mu}SH kuDEA.
| TVS faaaoH Is simply thiH: Yiio orbitn II The
earth around llIa Hill, atHt VI tho m0ol, Arn,lnl
the earth. xru nut situated u the sanlg plane.
Thur pxtaH make au al,gle Ut little mare tatl
| degrees with eacll other. Tl.erefnrH, unaeKt
tho f,.ll oseur vt A,u tins w.,bu tho Aou,
is yery nuar oile of tile tna points III which hot
| orbit antesseelA tic platte OF this aarlha mhit
| (the not|eu) rho will pasB either northwarl 0!
southwark IL the bl,al ow and nat atiiroreolipse
1T tbs prcBout instance the moon will ho nt,uohi
exactly in her merit. undo on entering tllo uu'
lrs, l1er eontre being then ut 4 iu ll,f tirs, dis
gra,u Hut Hho will bo lanying unstllwurl much
l,oro rapidly t,lau tho curtl, tho difraronco d
the narthwanl movements boiug lIttls
mora than qlattor nj degree ror lloue
IT, IN tho scennd diagram. tho al,rfsce Of Lii
paper represent tho plano Of Tho ocliptie. ther
she rnoon's eaHssa Will ba in ths paper whan III,
h IN thn poalt!o7. a. but vii b. aemo dtasapo