actively employed while you are professedly studying, your time is worse
than wasted, for you are acquiring habits of idleness, that will be most
difficult to lay aside.

You should always be engaged in some work that affords considerable
exercise to the mind--some book over the sentences of which you are
obliged to pause, to ponder--some kind of study that will cause the
feeling of almost physical fatigue; when, however, this latter sensation
comes on, you must rest; the brain is of too delicate a texture to bear
the slightest over-exertion with impunity.[74] Premature decay of its
powers, and accompanying bodily weakness and suffering, will inflict
upon you a severe penalty for any neglect of the symptoms of mental
exhaustion.[75] Your mind, however, like your body, ought to be
exercised to the very verge of fatigue; you cannot otherwise be certain
that there has been exercise sufficient to give increased strength and
energy to the mental or physical powers.

The more vigorous such exercise is, the shorter will be the time you can
support it. Perhaps even an hour of close thinking would be too much for
most women; the object, however, ought not to be so much the quantity as
the quality of the exercise. If your peculiarly delicate and sensitive
organization cannot support more than a quarter of an hour's continuous
and concentrated thought, you must content yourself with that.
Experience will soon prove to you that even the few minutes thus
employed will give you a great superiority over the six-hours-a-day
readers of your acquaintance, and will serve as a solid and sufficient
foundation for all the lighter superstructure which you will afterwards
lay upon it. This latter, in its due place, I should consider as of
nearly as much importance as the foundation itself; for, keeping
steadily in view that usefulness is to be the primary object of all your