before the chance for the observation occurs.

Pictures are less valuable as educational aids than objects; at best
they are but partially and imperfectly concrete. The study of pictures
tends to cultivate the imagination and taste, but observation and
judgment are but little exercised.

A comparison of the kind of knowledge gained in either of the above ways
with that gained by a study of science as such, will make some of the
advantages of the latter evident. An act of complete knowledge consists
in the identifying of an attribute with a subject. Attributes of
quality--of condition--of relation, may be gained from lessons in which
objects or pictures are used. Attributes of action which are unregulated
by the observer may be learned from the study of animals. But very
little of actions and changes which can be made to take place under
specified conditions, and with uniformity of result, can be learned
until physical science is drawn upon.

And yet consider the importance of such study. Changes around him appeal
most strongly to the child. "Why _does_ this thing _do_ as it _does_?"
is more frequent than "Why _is_ this thing as it _is_?" He sees changes
of place, of form, of size, of composition, taking place; his curiosity
is aroused; and he is ready to study with avidity, and in a systematic
manner, the changes which his teacher may present to him. Consider
the peculiarities belonging to the study of changes of any sort. The
interest is held, for the mind is constantly gaining the new. The
attention cannot be divided--all parts of the change, all phases of the
action, must be known, and to be known must be _observed_; while in
other forms of lessons the attention may be diverted for a moment to
return to the consideration of exactly what was being observed before.