of the earth by such efforts as have just been indicated.

When we go beyond the earth into the realm of the stars all efforts
toward understanding the ranges of space or the durations of time are
quite beyond the efforts of man. Even the distance of about two
hundred and forty thousand miles which separates us from the moon can
not be grasped by even the greater minds. No human intelligence,
however cultivated, can conceive the distance of about ninety-five
million miles which separates us from the sun. In the celestial realm
we can only deal with relations of space and time in a general and
comparative way. We can state the distances if we please in millions
of miles, or we can reckon the ampler spaces by using the interval
which separates the earth from the sun as we do a foot rule in our
ordinary work, but the depths of the starry spaces can only be sounded
by the winged imagination.

Although the student has been advised to begin his studies of Nature
on the field whereon he dwells, making that study the basis of his
most valuable communications with Nature, it is desirable that he
should at the same time gain some idea as to the range and scope of
our knowledge concerning the visible universe. As an aid toward this
end the following chapters of this book will give a very brief survey
of some of the most important truths concerning the heavens and the
earth which have rewarded the studies of scientific men. Of remoter
things, such as the bodies in the stellar spaces, the account will be
brief, for that which is known and important to the general student
can be briefly told. So, too, of the earlier ages of the earth's
history, although a vast deal is known, the greater part of the
knowledge is of interest and value mainly to geologists who cultivate
that field. That which is most striking and most important to the mass