If light matter were suggested by the spectrum of these
nebulae, it might be asked further, as a pure speculation, whether in
them we were witnessing possibly a later condensation of the light
matter which had been left behind, at least in a relatively greater
proportion, after the first growth of worlds into which the heavier
matter condensed, though not without some entanglement of the lighter
substances. The wide extent and great diffuseness of this bright-line
nebulosity over a large part of the constellation of Orion might be
regarded, perhaps, as pointing in this direction. The diffuse nebulous
matter streaming round the Pleiades might possibly be another
instance, though the character of its spectrum had not yet been
ascertained.
THE MOTIONS OF THE STARS.
Besides its more direct use in the chemical analysis of the heavenly
bodies, the spectroscope had given to us a great and unexpected power
of advance along the lines of the older astronomy. In the future a
higher value might, indeed, be placed upon this indirect use of the
spectroscope than upon its chemical revelations. By no direct
astronomical methods could motions of approach or of recession of the
stars be even detected, much less could they be measured.
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