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 capacities enable him to discern the operations
of Nature. Man, in common with his lower kindred, is, by the mechanism
of the body, provided with five somewhat different ways by which he
may learn something of the things about him. The simplest of these
capacities is that of touch, a faculty that is common to the general
surface of the body, and which informs us when the surface is affected
by contact with some external object. It also enables us to discern
differences of temperature. Next is the sense of taste, which is
limited to the mouth and the parts about it. This sense is in a way
related to that of touch, for the reason that it depends on the
contact of our body with material things. Third is the sense of smell,
so closely related to that of taste that it is difficult to draw the
line between the two. Yet through the apparatus of the nose we can
perceive the microscopically small parts of matter borne to us through
the air, which could not be appreciated by the nerves of the mouth.
Fourth in order of scope comes the hearing, which gives us an account
of those waves of matter that we understand as sound. This power is
much more far ranging than those before noted; in some cases, as in
that of the volcanic explosions from the island of Krakatoa, in the
eruption of 1883, the convulsions were audible at the distance of
more than a thousand miles away. The greater cannon of modern days may
be heard at the distance of more than a hundred miles, so that while
the sense of touch, taste, and smell demand contact with the bodies
which we appreciate, hearing gives us information concerning objects
at a considerable distance. Last and highest of the senses, vastly the