ld up the tissue of
every plant, to sustain the activity of every animal, including man,
upon the surface of our vast and stately globe. Considering the wondrous
richness and variety of the terrestrial life wrought out by the few
sunbeams which we catch in our career through space, we may well
pause overwhelmed and stupefied at the thought of the incalculable
possibilities of existence which are thrown away with the potent
actinism that darts unceasingly into the unfathomed abysms of immensity.
Where it goes to or what becomes of it, no one of us can surmise.

Now when, in the remote future, our sun is reduced to vapour by the
impact of the several planets upon his surface, the resulting nebulous
mass must be a very insignificant affair compared with the nebulous mass
with which we started. In order to make a second nebula equal in size
and potential energy to the first one, all the energy of position at
first existing should have been retained in some form or other. But
nearly all of it has been lost, and only an insignificant fraction
remains with which to endow a new system. In order to reproduce, in
future ages, anything like that cosmical development which is now
going on in the solar system, aid must be sought from without. We must
endeavour to frame some valid hypothesis as to the relation of our solar
system to other systems.

Thus far our view has been confined to the career of a single star,--our
sun,--with the tiny, easily-cooling balls which it has cast off in the
course of its development. Thus far, too, our inferences have been
very secure, for we have been dealing with a circumscribed group of
phenomena, the beginning and end of which have been brought pretty well
within the compass of our imagination. It is quite another thing to deal
with the actual or probable career of the stars in general, inasmuch
as we do not even know how many stars there are, which form parts of
a common system, or what are their precise dynamic relations to one
another. Nevertheless we have knowledge of a few facts which may support
some cautious inferences. All the stars which we can see are undoubtedly
bound together by relations of gravitation. No doubt our sun attracts
all the other stars within our ken, and is reciprocally attracted by
them. The stars, too, lie mostly in or around one great plane, as is the
case with the members of the solar system. Moreover, the stars are shown
by the spectroscope to consist of chemical e