field of Nature. For a time it was possible for any one able and
laborious man to know all which had been ascertained concerning
astronomy, chemistry, geology, as well as the facts relating to living
beings. The more, however, as observation accumulated, and the store
of facts increased, it became difficult for any one man to know the
whole. Hence it has come about that in our own time natural learning
is divided into many distinct provinces, each of which demands a
lifetime of labour from those who would know what has already been
done in the field, and what it is now important to do in the way of
new inquiries.

The large divisions which naturalists have usually made of their tasks
rest in the main on the natural partitions which we may readily
observe in the phenomenal world. First of all comes astronomy,
including the phenomena exhibited in the heavens, beyond the limits of
the earth's atmosphere. Second, geology, which takes account of all
those actions which in process of time have been developed in our own
sphere. Third, physics, which is concerned with the laws of energy, or
those conditions which affect the motion of bodies, and the changes
which are impressed upon them by the different natural forces. Fourth,
chemistry, which seeks to interpret the principles which determine the
combination of atoms and the molecules which are built of them under
the influence of the chemical affinities. Fifth, biology, or the laws
of life, a study which pertains to the forms and structures of animals
and plants, and their wonderful successions in the history of the
world. Sixth, mathematics, or the science of space and number, that
deals with the principles which underlie the order of Nature as
expressed at once in the human understanding and in the material
universe. By its use men were made able to calculate, as in
arithmetic, the problems which concern their ordinary business, as