well as to compute the movements of the celestial bodies, and a host
of actions which take place on the earth that would be inexplicable
except by the aid of this science. Last of all among the primary
sciences we may name that of psychology, which takes account of mental
operations among man and his lower kindred, the animals.

In addition to the seven sciences above mentioned, which rest in a
great measure on the natural divisions of phenomena, there are many,
indeed, indefinitely numerous, subdivisions which have been made to
suit the convenience of students. Thus astronomy is often separated
into physical and mathematical divisions, which take account either of
the physical phenomena exhibited by the heavenly bodies or of their
motions. In geology there are half a dozen divisions relating to
particular branches of that subject. In the realm of organic life, in
chemistry, and in physics there are many parts of these sciences which
have received particular names.

It must not be supposed that these sciences have the independence of
each other which their separate names would imply. In fact, the
student of each, however, far he may succeed in separating his field
from that of the other naturalists, as we may fitly term all students
of Nature, is compelled from time to time to call 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