in the
heavens and a star that cannot be seen by the naked eye, prove to be
equidistant, relative distances cannot be in the least inferred from
relative visibilities. And if so, nebulae may be comparatively near,
though the starlets of which they are made up appear extremely minute.

On the other hand, what follows if the truth of the assumption be
granted? The arguments used to justify this assumption in the case of
the stars, equally justify it in the case of the nebulae. It cannot be
contended that, on the average, the _apparent_ sizes of the stars
indicate their distances, without its being admitted that, on the
average, the _apparent_ sizes of the nebulae indicate their
distances--that, generally speaking, the larger are the nearer and the
smaller are the more distant. Mark, now, the necessary inference
respecting their resolvability. The largest or nearest nebulae will be
most easily resolved into stars; the successively smaller will be
successively more difficult of resolution; and the irresolvable ones
will be the smallest ones. This, however, is exactly the reverse of the
fact. The largest nebulae are either wholly irresolvable, or but
partially resolvable under the highest telescopic powers; while large
numbers of quite small nebulae are easily resolved by far less powerful
telescopes. An instrument through which the great nebula in Andromeda,
two and a half degrees long and one degree broad, appears merely as a
diffused light, decomposes a nebula of fifteen minutes diameter into
twenty thousand starry points. At the same time that the individual
stars of a nebula eight minutes in diameter are so clearly seen as to
allow of their number being estimated, a nebula covering an area five
hundred times as great shows no stars at all! What possible explanation
of this can be given on the current hypothesis?

Yet a further difficulty remains--one which is, perhaps, still more
obviously fatal than the foregoing. This difficulty is presented by the
phenomena of the Magellanic clouds. Describing the larger of these, Sir
John Herschel says:--

"The Nubecula Major, like the Minor, consists partly of large
tracts and ill-defined patches of irresolvable nebula, and of
nebulosity in every stage of resolution, up to perfectly resolved
stars like the Milky Way, as also of regular and irregular nebulae
properly so called, of globular clusters in every stage of
resolvability, and of clustering g