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