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

tilmes sce Satllurn's rinll unlfder thle formn of a blroad ellipsce,
whichl grows cot1tinallay iuore anlild:ltore nlarrow: intil it p)asscs.
into a linl, alid we aithler:lost sig'ht of it: altogt t:ht'l', V \ith
thle aid of t lie most p1)oxefilul telescopes, \Ce see it as a line linle'
drallt aeross thle (lisk, atd p: ojectilnX, oult fiolm it onI eatll side.
fAs the whtole revolltion occ upies nClarly 30 year, allnd the piano
of tle rilg passes across tlle earthl's orbtitv twice il tteC revo(lition, tlhe llcnomc a at(3ttndinl(g' thl edge, view oYccu ( cvc ry l15
years, when tthe ring lmay withinll at single year disa:ppear rcpeatedly, andt for dliflerent reasons, as described in Ait. 34-L6.
344. T'.llc learner may pCerhaps ain a clearer idea of the
foregoing a l)leancs firom thleo following diagram.
Loet A, 1B, C, &c., l'ig1. 66, replresclnt successive positions of
Saturn andl his ring in diflrent parlts of Iris orbit, whlile (1
Fig. 66.
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repre)sents the orbit of the earth.'* l' i the lil \g l when at 0
an1d G perpc )edicular to the line joining CG-, it \ ould bo e sccn
by a spectator situated at a or b as a perfEct; circle, but being
inclined to the line of visioIn 28 11.', it ihs )prjected into an
ellipse. TIis ellipse gradtuall1y contracts to a stzraioht. line, as
the ring passes to A an(ld 1, whgere its nodes are in the dieetiolt of tlhe earthl's orbit.:lrom I1 to C- tlut ellpse widens
again, till at (: tile lbreadtht is nelarly vhalf as g-rieat as its length.
Tllrough thle quadrant fiom (CI to A. it contracts, and from A
to C it exp)ands, occuptying about 7' ye'arsn in goingl firom the
It 1tm any be remallrkeI by te letarner, that these orbits are maitte so elliptical,
not to rcletceslxt the,neam.ii!, of either the earth's or 1Sturn's orbit, but merely
ns the prljection of circles ceet vcr)' oblitllely.