s of stars, comparable to our own galactic
system.

But the inference was wrong; for when the spectroscope was first applied
to a nebula in 1864, by Dr. Huggins, it clearly showed the spectrum not
of discrete stars, but of a great mass of glowing gases, hydrogen among
others. More extended studies showed, it is true, that some nebulae give
the continuous spectrum of solids or liquids, but the different types
intermingle and grade into one another. Also, the closest affinity
is shown between nebulae and stars. Some nebulae are found to contain
stars, singly or in groups, in their actual midst; certain condensed
"planetary" nebulae are scarcely to be distinguished from stars of the
gaseous type; and recently the photographic film has shown the presence
of nebulous matter about stars that to telescopic vision differ in no
respect from the generality of their fellows in the galaxy. The familiar
stars of the Pleiades cluster, for example, appear on the negative
immersed in a hazy blur of light. All in all, the accumulated
impressions of the photographic film reveal a prodigality of nebulous
matter in the stellar system not hitherto even conjectured.

And so, of course, all question of "island universes" vanishes, and the
nebulae are relegated to their true position as component parts of the
one stellar system--the one universe--that is open to present human
inspection. And these vast clouds of world-stuff have been found by
Professor Keeler, of the Lick observatory, to be floating through space
at the starlike speed of from ten to thirty-eight miles per second.

The linking of nebulae with stars, so clearly evidenced by all these
modern observations, is, after all, only the scientific corroboration of
what the elder Herschel's later theories affirmed. But the nebulae have
other affinities not until recently suspected; for the spectra of some
of them are practically identical with the spectra of certain comets.
The conclusion seems warranted that comets are in point of fact minor
nebulae that are drawn into our system; or, putting it otherwise, that
the telescopic nebulae are simply gigantic distant comets.

Lockyer's Meteoric Hypothesis

Following up the surprising clews thus suggested, Sir Norman Lockyer,
of London, has in recent years elaborated what is perhaps the most
comprehensive cosmogonic guess that has ever been attempted. His theory,
known as the "meteoric hypothesis," probably bears the same relation
to the