are entitled to be regarded as real suns, and they vary enormously in
magnitude. The effects of their attractions upon one another can only
be inferred from their clustering, because their relative movements
are not apparent on account of the brevity of the observations that we
can make. But imagine a being for whom a million years would be but as
a flitting moment; to him the Milky Way would appear in a state of
ceaseless agitation -- swirling with ``a fury of whirlpool motion.''

The cloud-like aspect of large parts of the Galaxy must always have
attracted attention, even from naked-eye observers, but the true
star-clouds were first satisfactorily represented in Barnard's
photographs. The resemblance to actual clouds is often startling. Some
are close-packed and dense, like cumuli; some are wispy or mottled,
like cirri. The rifts and modulations, as well as the general
outlines, are the same as those of clouds of vapor or dust, and one
notices also the characteristic thinning out at the edges. But we must
beware of supposing that the component suns are thickly crowded as the
particles forming an ordinary cloud. They look, indeed, as if they
were matted together, because of the irradiation of light, but in
reality millions and billions of miles separate each star from its
neighbors. Nevertheless they form real assemblages, whose members are
far more closely related to one another than is our sun to the stars
around him, and if we were in the Milky Way the aspect of the
nocturnal sky would be marvelously different from its present
appearance.

Stellar clouds are characteristic of the Galaxy and are not found
beyond its borders, except in the ``Magellanic Clouds'' of the
southern hemisphere, which resemble detached portions of the Milky
Way. These singular objects form as striking a peculiarity of the