ven matter itself may be a product of evolution. The astronomer finds
it difficult to conceive that the great nebulous masses which he sees
in the celestial spaces--millions of times larger than the whole solar
system, yet so tenuous that they offer not the slightest obstruction to
the passage of a ray of light through their whole length--situated in
what seems to be a region of eternal cold, below anything that we can
produce on the earth's surface, yet radiating light, and with it heat,
like an incandescent body--can be made up of the same kind of substance
that we have around us on the earth's surface. Who knows but that the
radiant property that Becquerel has found in certain forms of matter
may be a residuum of some original form of energy which is inherent in
great cosmical masses, and has fed our sun during all the ages required
by the geologist for the structure of the earth's crusts? It may be
that in this phenomenon we have the key to the great riddle of the
universe, with which profounder secrets of matter than any we have
penetrated will be opened to the eyes of our successors.

IV

THE EXTENT OF THE UNIVERSE

We cannot expect that the wisest men of our remotest posterity, who can
base their conclusions upon thousands of years of accurate observation,
will reach a decision on this subject without some measure of reserve.
Such being the case, it might appear the dictate of wisdom to leave its
consideration to some future age, when it may be taken up with better
means of information than we now possess. But the question is one which
will refuse to be postponed so long as the propensity to think of the
possibilities of creation is characteristic of our race. The issue is
not whether we shall ignore the question altogether, like Eve in the
presence of Raphael; but whether in studying it we shall confine our
speculations within the limits set by sound scientific reasoning.
Essaying to do this, I invite the reader's attention to what science
may suggest, admitting in advance that the sphere of exact knowledge is
small compared with the possibilities of creation, and that outside
this sphere we can state only more or less probable conclusions.

The reader who desires to approach this subject in the most receptive
spirit should begin his study by betaking himself on a clear, moonless
evening, when he has no earthly concern to disturb the serenity of his
thoughts, to some point where he can lie on his back