d of certain views taken by Olbers as to a defect of perfect
transparency in the celestial spaces, in virtue of which the light of
the more distant stars is enfeebled more than in proportion to their
distance. The extinction of light thus originating proceeding in
geometrical ratio, while the distance increases in arithmetical, a
limit, it is argued, is placed to the space-penetrating power of
telescopes far within that which distance alone, apart from such
obscuration, would assign.

It must suffice here to observe that the objection alluded to, if
applicable to any, is equally so to every part of the galaxy. We are not
at liberty to argue that at one part of its circumference our view is
limited by this sort of cosmical veil, which extinguishes the smaller
magnitudes, cuts off the nebulous light of distant masses, and closes
our view in impenetrable darkness; while at another we are compelled, by
the clearest evidence telescopes can afford, to believe that star-strewn
vistas _lie open_, exhausting their powers and stretching out beyond
their utmost reach, as is proved by that very phenomenon which the
existence of such a veil would render impossible--_viz._, infinite
increase of number and diminution of magnitude, terminating in complete
irresolvable nebulosity.

Such is, in effect, the spectacle afforded by a very large portion of
the Milky Way in that interesting region near its point of bifurcation
in Scorpio, where, through the hollows and deep recesses of its
complicated structure, we behold what has all the appearance of a wide
and indefinitely prolonged area strewed over with discontinuous masses
and clouds of stars, which the telescope at last refuses to analyse.
Whatever other conclusions we may draw, this must anyhow be regarded as
the direction of the greatest linear extension of the ground-plan of the
galaxy. And it would appear to follow also that in those regions where
that zone is clearly resolved into stars well separated and _seen
projected on a black ground_, and where, by consequence, it is certain,
if the foregoing views be correct, that we look out beyond them into
space, the smallest visible stars appear as such not by reason of
excessive distance, but of inferiority of size or brightness.

_III.--Variable, Temporary and Binary Stars_

Wherever we can trace the law of periodicity we are strongly impressed
with the idea of rotatory or orbitual motion. Among the stars are
several which, thoug