g superficial, has been my aim
throughout.

In neither volume have I aspired to sit in the seat of the scornful,
but rather to treat the questions touched upon with a tolerance, if
not a reverence, befitting their difficulty and weight.

Holding, as I do, the nebular hypothesis, I am logically bound to
deduce the life of the world from forces inherent in the nebula. With
this view, which is set forth in the second volume, it seemed but fair
to associate the reasons which cause me to conclude that every attempt
made in our day to generate life independently of antecedent life has
utterly broken down.

A discourse on the Electric Light winds up the Second volume. The
incongruity of its position is to be referred to the lateness of its
delivery.

********************

VOL. I. INORGANIC NATURE.

I. THE CONSTITUTION OF NATURE.

[Footnote: 'Fortnightly Review,' 1865, vol. iii. p. 129.]

WE cannot think of space as finite, for wherever in imagination we
erect a boundary, we are compelled to think of space as existing
beyond it. Thus by the incessant dissolution of limits we arrive at a
more or less adequate idea of the infinity of space. But, though
compelled to think of space as unbounded, there is no mental necessity
compelling us to think of it either as filled or empty; whether it is
so or not must be decided by experiment and observation. That it is
not entirely void, the starry heavens declare; but the question still
remains, Are the stars themselves hung in vacuo? Are the vast
regions which surround them, and across which their light is
propagated, absolutely empty? A century ago the answer to this
question, founded on the Newtonian theory, would have been, 'No, for
particles of light are incessantly shot through space.' The reply of
modern science is also negative, but on different grounds. It has the
best possible reasons for rejecting the idea of luminiferous
particles; but, in support of the conclusion that the celestial spaces
are occupied by matter, it is able to offer proofs almost as cogent as
those which can be adduced of the existence of an atmosphere round the
earth. Men's minds, indeed, rose to a conception of the celestial and
universal atmosphere through the study of the terrestrial and local
one. From the phenomena of sound, as displayed in the air, they
ascended to the phenomena of light, as displayed in the _aether_; which
is the name given to the interstellar medium.

The notion