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

296 FSx;PD) s''AtS.
giving::gsi/sns of resolvabilitty, but its perfect rcsolultion has not
been attained. Slould it b)e acllieved by an i rlecased power
of the illstrumetnt) astronomers look for a splendid coronet of
stars, Imori' glorious, rhaps, thflan any thing hitllelrto discovered
in the stalrry hleavets.
Planeftaitiy jNciw const-itute another variCty, and are very
remalrkable objects.'ltey have, as their name imports, exactly
thle appearance of planets. Whatever nmay be their nature,
they mlltust bt of 11ormous11101S magnll itude. One of thelm is to be
found in the 1arallel of v Aquartlii, anlid about 5mI. )rceding
that star. lilts apparent difanitctr is about 20". Another ill
tihe conlstllation Andromeda, presents a visible disk of 12",
perfectly d(lefiled and round. G-(ranting these obljects to be
equally distafit fr'om us with the stars, their real dimelsiollns
must hie siuchl as, on tc lowest compulltation, would fill the orbit oft Urantl. i[t is no less evident thiat, if they be solid
bodies, of a solar nature, the intrinsic splendor of their surfaces
must be at lmost infinitely infelrior to that of the iun. A circular
portion of tlhet sun's disk, subtending an angle of 20", Nwould give
a ligllt equal to 100 fill moons; while tihe olbjects ill question
are hardly, if at; all, discernible with the naked ee.'x'
428. Thotie.IZil'ty, or Gala:,xy, is a wevll-known luii11nos zone, nlirclilng the sphere nearly in the direction of a
g;tat circle. Near the Swan, in the northern'l sky, it is seen
t j be divided into two bands, whichl remainl asunder for 15oU0
and thtn reunite. h'lhe (CGalaxy owes its peculiar appealrace
to tlhe blended light of mylriads of small stars too minute to )e
intdividiually recogtlized by the lc Laked eye, but whichl are seen
i tleir ti te character by a telescope of only )moderate poweres.
Sir William Illrs1 el estimated, t.llat, on one occasion, i folrtyon0e Iminttes, no less than S2058,000 stars patssed tllroughl tht
smlll field of 1his telescope.t' nl. approaching the bordXerti of
the -MAilky Way, there is found a regiular but 1rapid increase i'ir
th1e numb)er of stars, even before entering the limits of tlhe htmillolus zolne itself. Sir J. I:elrschecl computes the whole 1ule 1lict.ischlt..
Plate It., Fig. I, exhibits a telescopic view of a part of the southern portion
of the Milky \.Way\