ll in the aid of his
brethren who cultivate other branches of learning. The modern
astronomer needs to know much of chemistry, or else he can not
understand many of his observations on the sun. The geologists have to
share their work with the student of animal and vegetable life, with
the physicists; they must, moreover, know something of the celestial
spheres in order to interpret the history of the earth. In fact, day
by day, with the advance of learning, we come more clearly to
perceive that all the processes of Nature are in a way related to each
other, and that in proportion as we understand any part of the great
mechanism, we are forced in a manner to comprehend the whole. In other
words, we are coming to understand that these divisions of the field
of science depend upon the limitations of our knowledge, and not upon
the order of Nature itself. For the purposes of education it is
important that every one should know something of the great truths
which each science has disclosed. No mortal man can compass the whole
realm of this knowledge, but every one can gain some idea of the
larger truths which may help him to understand the beauty and grandeur
of the sphere in which he dwells, which will enable him the better to
meet the ordinary duties of life, that in almost all cases are related
to the facts of the world about us. It has been of late the custom to
term this body of general knowledge which takes account of the more
evident facts and important series of terrestrial actions
physiography, or, as the term implies, a description of Nature, with
the understanding that the knowledge chosen for the account is that
which most intimately concerns the student who seeks information that
is at once general and important. Therefore, in this book the effort
is made first to give an account as to the ways and means which have
led to our understanding of scientific problems, the methods by which
each person may make himself an inquirer, and the outline of the
knowledge that has been gathered since men first began to observe and
criticise the revelations the universe may afford them.

CHAPTER II.

WAYS AND MEANS OF STUDYING NATURE.

It is desirable that the student of Nature keep well in mind the means
whereby he is able to perceive what goes on in the world about him. He
should understand something as to the nature of his senses, and the
extent to which these capacit