e whole conscious process.

=Attention and Knowledge.=--Mention has already been made of the
relation of attention to interest. It should be noted, further, that the
difference in our attention under different circumstances is largely
dependent upon our knowledge. The stonecutter, as he passes the fine
mansion, gives attention to the fretted cornice; the glazier, to the
beautiful windows; the gardener, to the well-kept lawn and beds. Even
the present content of the mind has its influence upon attention. The
student on his way to school, if busy with his spelling lesson, is
attracted to the words and letters on posters and signs. If he is
reviewing his botany, he notes especially the weeds along the walk; if
carrying to his art teacher, with a feeling of pride, the finished
landscape drawing, his attention goes out to the shade and colour of
field and sky. That such a connection must exist between knowledge and
attention is apparent from what has been already noted concerning the
working of the law of apperception.

=Physical Conditions of Attention.=--From what was learned above
regarding the relation of nervous energy to active attention, it is
evident that the ability to attend to a problem at any given time will
depend in part upon the physical condition of the organism. If,
therefore, the nervous energy is lowered through fatigue or sickness,
the attention will be weakened. For this reason the teaching of
subjects, such as arithmetic, grammar, etc., which present difficult
problems, and therefore make large demands upon the attention of the
scholars, should not be undertaken when the pupils' energy is likely to
be at a minimum. Similarly, unsatisfactory conditions in the
school-room, such as poor ventilation, uncomfortable seats, excessive
heat or cold, all tend to lower the nervous energy and thus prevent a
proper concentration of attention upon the regular school work.

=Precautions Relating to Voluntary Attention.=--Although voluntary
attention is evidently the form of attention possessing real educational
value, certain precautions would seem necessary concerning its use. With
very young children the aim for attending should evidently not be too
remote. In other words, the problem should involve matter in which the
children have a direct interest. For this reason it is sometimes said
that young children should set their own problems. This is of course a
paradox so far as the regular school work is concerned, t