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

being sup-posed such thlat tflo rays of lighlt come from them all
to thl e e lnearly par.allel. iNowm let the axis, instead of being
)perpendilictular to the line of vision, b0 ilnclined to that lile,
then all the rings beinlg seen obliquely, would be )jroieted
into ellipses. It, howcver, while the sphrc rem1ained inl a
fixed position, the eye wyt ere carried aroutlll it (being always i n
thce sanec plane) twice duriiig tlhe circuit, it would be in th-el
1pltne of thc cquator, anld project t.his and a11 the smaller
circles into straight lines; and twice, at points 90~ distant firoml
thel foregoilg positions, the eye \would be at a distance3 fi'om
the palItits of the rings equal to the inclination of the equator
of the sphere to the line of vision. 1Here it would project the
rincigs' into Nwideir ellipses than at otlher poinllts; andll tihe ellipses
would becomle mole and mor eccentric as the eye del)arttc
fioml citlher of tflese point.s, until they vanlishlcd:againC inlto
straight lines.
150. It is in a similar ma nner that the eye viws the paths
described by the spots on the snm. If the sun revolved on an
axis perpendllicular to the p1lane of teic earth's orbit, tie eye t)eing situated iln the plane1 of revolutiolln, and at such a distance
firom the sun tlhat thle light comlnes to thle eye fi'om all patts of
the solal disk nearly parallel, the p1aths described by the spo v};ts
would be projlcted into strtaitIght lines, arnd eaclt would dcscrib
a st raight line across the solar disk, parallel to the pltnle of
revolution. Blut thle axis of the slun is iItclillctt to tthe celiptic
about T7}0 friom a pe){rpendicularl so tlhat ustally all tthe cirhcles
desecribed by thle spots arte projected into ellipses. XThe breadth
of these, h.towever, will vary as the eye, in the annual revolution, is carried aroulnd thle sun, and when th l e)e ecomes into
the plane of the rings, as it does twiee af. y ear, thley are projectedl into straight liies, anid for a short time a spot seems
mloving' in a staiight line inclined to the planeto of the celiptic
7-0 The two points whiere the sun's equator cuts the ecliptic
are called tThe sun's nodtes. Tlhe longitudes of ftlo nodes alre
800 7' aiid 260 7', and ttlo eartlh iasses throulgh them a)bout
tihe:1.2th of ]:).esti)er, and thle:1'th of Junle. It is at thles-e
tinles that the spots appear to describe straight lines. \We
hlave mentioned the various chtanges in t lte apparent pathis of
the solar spots, which arise fiont the inclination of the suln'