phenomena of the solar system.
* The mystery of the Zodiacal Light and the Gegenschein.
* The extraordinary transformations undergone by comets and their
tails.
* The prodigies of meteorites and masses of stone and metal fallen
from the sky.
* The cataclysms that have wrecked the moon.
* The problem of life and intelligence on the planet Mars.
* The problematical origin and fate of the asteroids.
* The strange phenomena of the auroral lights.

An attempt has been made to develop these topics in an orderly way,
showing their connection, so that the reader may obtain a broad
general view of the chief mysteries and problems of astronomy, and an
idea of the immense field of discovery which still lies, almost
unexplored, before it.

The Windows of Absolute Night

To most minds mystery is more fascinating than science. But when
science itself leads straight up to the borders of mystery and there
comes to a dead stop, saying, ``At present I can no longer see my
way,'' the force of the charm is redoubled. On the other hand, the
illimitable is no less potent in mystery than the invisible, whence
the dramatic effect of Keats' ``stout Cortez'' staring at the
boundless Pacific while all his men look at each other with a wild
surmise, ``silent upon a peak in Darien.'' It is with similar feelings
that the astronomer regards certain places where from the peaks of the
universe his vision seems to range out into endless empty space. He
sees there the shore of his little isthmus, and, beyond, unexplored