remember fairly well the extent of our knowledge when we had reached your
stage. If I should fall into the error of attributing to you more than you
have already discovered you can easily correct me.

"If, now, you leave the little group of dark bodies which are so like the
earth, and go out still further into space, what do you find? At distances
so great that only the speed of light can be used as a measuring line, you
discover vast numbers of self-luminous bodies, which you call stars. Your
natural eye can tell but a small fraction of their number. For example,
look at the constellation you have named the Pleiades and you see six or
seven stars. View it through a three-inch telescope and you can count
perhaps three hundred. Now attach a photographic plate to the telescope,
and with an exposure of four hours the light coming from that small patch
of sky falls upon the sensitive film with a cumulative effect until you
have a picture of more than two thousand three hundred stars."

"Yes," broke in the doctor, "you are gauging correctly the state of our
knowledge. Our largest telescopes reveal in the entire sky, it is said,
one hundred million stars."

"Then," answered Thorwald, "if the glories of the heavens were made merely
to delight the eye of man, why was not the eye created of sufficient power
to behold them? As it is, only a small proportion of the stars can be seen
without the aid of instruments too costly and too delicate for general
use.

"But have you the means of establishing any likeness between the earth and
those distant bodies? You have discovered that the law of gravitation is
universal and that the motions of the stars resemble those of the solar
system. Have you made any discoveries tending to prove the existence of