The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1878-07-28

sun, while erescsns shaped surface will remain
posed on tho opposite side.
EcLiPsRs. LUNAR TERN EsrRiAL
Having explained briefly tho mediate causes Of
eclipses OF the sun the reader Will consider The
movements OF the earth and moon that bring about
these phenomena the peculiar relative position
sumed oy these bodies with regard each o.he to
the sun which precede and solipses
The earth In It's annual movement around the sun
performs the journey through space ellipRcai,
not circular orbit. The exact time OF this revotu-
ton oil she earth around The sun in mean solar days
Is 800 days. hours, minutes 1,075 LOO seconds Ia
this Time tho earth makes the full circuIt OF its
orbit, arriving again at It's point Of departure or
tho etipse SO described the sun ferns OF the
foci or generating points The mean distance Of the
sun from tho earth has been recently caleu-
lated from observations OF the transit OF
Venus to be about %, 800. 900 miles, nearly Two
millions Of miles less than the distance previously
accepted by astronomers as correct Tho average
rate OF movement of the earth ellpica orbit 10
estimated at IS 900 miles hsur This gives direct
moon OF the earth through space OF nineteen mibis
second Now, travelling as 1t does, on the crcuin-
ference Of an ellpse OF which The ! at locus.
the distance between the earth and the
ssAn'ly changing AS also 10 uas rate OF tao esrths
motion on IT'S orbit
The moon, beng tho eapths satellite, revolves
around her, also following an cllipticai course. OF
which the earth OF tho foci by OF which
the moons distance from thA, earth apparent
size are constantly changing Again. the orbit OF tho
moon around the earth lorna with that OF the earth
around the sun oil the eclipnc angle OF tive de-
grees and in its monthly revolution in,ersocts the
earth's orbit twice, its relative rate OF motion per
die m being 10 the apparent motion OF the tnr-
10 IN degrees TO degree. IL follows that
etn periods assumes position with relation TO the
sun and to The earth which place 1t In with
or opposition TO tho former. Whom tho Is on
the eclptc twice In each month It arrives at itx
NODES, which are distinguished by the terms ''ss-
csnding node" when the moon is passing IRON .he
south to The north Of the scptc, and 'sdesoon,nng
node" when II Is passing from the north 10 the
OF That line. II tho sciiptic was in tho same
plane as tho moons orbit there would be
two eclipses per lunar monsh-one OF the
sun and one If tho moon. Owing, however, to the
non-coincdence Of the two planes the lunar shadow
at new moon and the carth's shaaow full moon do
not always strike the earth and respectively,
as they must do TO cause eclipses OF the and
moon. II the nodes remained unchan ged In their re-
laton to the sun there would either be bimon THY
eelpses or mono ut ALL but as they constantly
change with tho earh's and moons courses along
ellptcai orbits, ecpses cannot occur unless the
phases OF new and full moon coin eide with the
nodes. Partial eclipses when the fuu
moon is very near, but not exactly, at tho nodes
that Is whom the earth Is In the ms penumbra,
the moon in that Of the earth.
Annular eclpses Of the sun occur when the phase
OF new moon corresponds with the node and when
she is at such distance from the nth that the apex
OF her Of shadow does reach tho surface Of
the earth.
THE PATH TOTAL EcLnosE.
This is determined by the direction taken the
surface OF the rotating earth by the uinbra oil the
moon. When the earth. whirhng through space ar
rives that point where the mooas cone OF shadow
6rst strikes the surfaoe, is revolving from
east. The motion oil the moon from west In
combination with that of the earth and tho fxcu centre
OF light the sun, the moons shadow otraverse
Of a width which is equal to the diameter of
the shadow where il strikes the sarihs surface.