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

M A RS. 193
about the timel t he su cts, sturprises us by his magnitude and
splendorl; but when lie passes to the other side of the sun to
his sup)erior conjunction, lie dwindles to the appearance of a
small star, beilng then 24J0,000,000 miles from us., Thus, let A-.
Fig. 64.
Q ~.
(Fig. 6I —) represent Mitars iln opposition, and'AT in superiior
conjunction, it is obvious that tlhe plancet must be nearer to lus
ln thle formcer situatiol thian in the latter by the whole diameter of tlhe eartlh's orbit.'322. Altars is the only one of the sul)erior planets which
exllibits plhlases.'When lce is toward the quadratures at Q or
Q', it is evident fom the fligure tlhat only a part of the circle
of illumination is turlln'ed toward tll cart, sucl a portion of
the remoter part of it being concealed firom our view as to
render thel form more or less gibtbous.
323. When viewted with a lowerful telescope, thle surface
of Martls appears (lidversifiel with nIumelrotus varieties of light
and slladlc..Thle region arlound the poles is marked by \white
spots, whlich vary their a)lppearance with the changes of tlle
seasons in tle planet. Ielnce lOr. iterscelle conjecturled tlhat
they are owing to ice or snow whlichl occasionally) accumulates
alnd 1ll1cts according to the position of eacll pole with respcct
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