have learned how to "erase all previous impressions." The
concentration which enables us all through life to be intent upon
the one thing we are doing, whether it is tennis or trigonometry,
and drop what we have in hand at once and entirely at the right
time, free to give out attention fully to the next duty or pleasure,
is our saving health in mind and body. The trouble is we are afraid.
We have no trust. A child is afraid to stop thinking of a lesson
after it is learned,--afraid he will forget it. When he has once
been persuaded to drop it, the surprise when he takes it up again,
to find it more clearly impressed upon his mind, is delightful. One
must trust to the digestion of a lesson, as to that of a good
wholesome dinner. Worry and anxiety interfere with the one as much
as with the other. If you can drop a muscle when you have ceased
using it, that leads to the power of dropping a subject in mind; as
the muscle is fresher for use when you need it, so the subject seems
to have grown in you, and your grasp seems to be stronger when you
recur to it.

The law of rhythm must be carefully followed in this training for
the use of the mind. Do not study too long at a time. It makes a
natural reaction impossible. Arrange the work so that lessons as far
unlike as possible may be studied in immediate succession. We help
to the healthy reaction of one faculty, by exercising another that
is quite different.

This principle should be inculcated in classes, and for that purpose
a regular programme of class work should be followed, calculated to
bring about the best results in all branches of study.

The first care should be to gain quiet, as through repose of mind