sometimes connected by a thread of light; when
their diameters are greater their forms vary--some are elongated, others
have several branches, some are fan-shaped, some annular, the ring being
well defined and the interior dark. They are supposed to be undergoing
various and progressive changes of form, as condensation proceeds around
one or more nuclei in conformity with the laws of gravitation. Between
two and three thousand of such unresolvable nebulae have already been
counted, and their positions determined.

If we leave the consideration of the attenuated vaporous matter of the
immeasurable regions of space, whether existing in a dispersed state as
a cosmical ether without form or limits, or in the shape of nebulae, and
pass to those portions of the universe which are condensed into solid
spheres or spheroids, we approach a class of phenomena exclusively
designated as stars or as the sidereal universe. Here, too, we find
different degrees of solidity or density in the agglomerated matter.

If we compare the regions of space to one of the island-studded seas of
our planet, we may imagine we see matter distributed in groups, whether
of unresolvable nebulae of different ages condensed around one or more
nuclei, or in clusters of stars, or in stars scattered singly. Our
cluster of stars, or the island in space to which we belong, forms a
lens-shaped, flattened, and everywhere detached stratum, whose major
axis is estimated at seven or eight hundred, and its minor axis at a
hundred and fifty times, the distance of Sirius. If we assume that the
parallax of Sirius does not exceed that accurately determined for the
brightest stars in Centaur (0.9128 sec.), it will follow that light
traverses one distance of Sirius in three years, while nine years and a
quarter are required for the transmission of the light of the star 61
Cygni, whose considerable proper motion might lead to the inference of
great proximity.

Our cluster of stars is a disc of comparatively small thickness divided,
at about a third its length, into two branches; we are supposed to be
near this division, and nearer to the region of Sirius than to that of
the constellation of the Eagle; almost in the middle of the starry
stratum in the direction of its thickness.

The place of our solar system and the form of the whole lens are
inferred from a kind of scale--_i.e._, from the different number of
stars seen in equal telescopic fields of view. The greater or