An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

'.06 TlE SUN.
thesetlves. 1:litt if a globoe wtcre cut out: of thle earth (tak1ingl:r
thalf thlle pol ar diametcr for radius), it would leave a protutiber<nilt iSa of matttter il tltle equatorial rcgiomls wlicht mllay b
considerled as all collectedl into a rin'g resting( on tlhe eart.ll
lTh sml bcing in the ecliptic, wvlile the plane of tlhis iln i-s
inclined to the eclipttic 23~ 28', of coutrse thle actionl ot thoe suin is
obl1ique to the rintg, and Imay bte resolved into twvo foctes one
in the plan e of the eqrator, <and the other perpendiicular to it.
tlhe latter only ean_ act as a disturbing fo)rce, and tendllclint as
it doest to dtra (towlt the ring to tlhe ecliptic, the inlg \Nvould
turn ll Ofll tile line of the equintoxes as upon a hinte, and
drahgglli the Cartll alonug t it, t lt tleequlator wouli ultimately
coincide w\ith the ecliptic, wlere it not for the revolution of the
Fig. 42.
h' \ ).............
earth upon its axis. Let 5C (VFig. 40) be the ccli ptic, and QitZ
the equator. Any particle A, of thle ring, by its inertia of
rotatioll tends to move towa\rtd in the plane QIt. Let VABI
represent this forcc, alltd.Ai the pressure tow\ard'' lroltuc
by the sunll; tihet the resultant will be Al); shiftingt tle
equintox backtwarld ftom T to T'. ]'Each]. particle is su. bjected
to thlis influencce, e xcept at tlt moment (each day) of crossing
T and s..% So long' (as the St1ul is ot himself in' the linC qelle. ^- 1p oduced, whtich occurs in Tarcht and September. The effect is
then intterruptet c ftor a slhort time.
192. The llooll consp)ires with the sut inI ptIroducing the
precession of the equinoxes, its cffet, oil acceount of its nearness
to the cartht, beillg More tan doublle that of the lsun, o1 as 7
to 3. Th1t p)lanets likcwise, by their attraction, prodluce a