lties will melt rapidly away before him. He possesses one key
to successful achievement.

MENTAL WANDERING.--_Second_, we may have good mental power and be able
to think hard and efficiently on any one point, but lack the power to
think in a straight line. Every stray thought that comes along is a
"will-o'-the-wisp" to lead us away from the subject in hand and into
lines of thought not relating to it. Who has not started in to think on
some problem, and, after a few moments, been surprised to find himself
miles away from the topic upon which he started! Or who has not read
down a page and, turning to the next, found that he did not know a word
on the preceding page, his thoughts having wandered away, his eyes only
going through the process of reading! Instead of sticking to the _a_,
_b_, _c_, _d_, etc., of our topic and relating them all up to A, thereby
reaching a solution of the problem, we often jump at once to _x_, _y_,
_z_, and find ourselves far afield with all possibility of a solution
gone. We may have brilliant thoughts about _x_, _y_, _z_, but they are
not related to anything in particular, and so they pass from us and are
gone--lost in oblivion because they are not attached to something
permanent.

Such a thinker is at the mercy of circumstances, following blindly the
leadings of trains of thought which are his master instead of his
servant, and which lead him anywhere or nowhere without let or hindrance
from him. His consciousness moves rapidly enough and with enough force,
but it is like a ship without a helm. Starting for the intellectual port
_A_ by way of _a_, _b_, _c_, _d_, he is mentally shipwrecked at last on
the rocks _x_, _y_, _z_, and never reaches harbor. Fortunate is he who
can shut out intruding thoughts and think in a straight line. Even with
mediocre ability he may accomplish more by his thinking than the
brilliant thinker who is constantly having his mental train wrecked by
stray thoughts which slip in on his right of way.

5. TYPES OF ATTENTION

THE THREE TYPES OF ATTENTION.--Attention may be secured in three ways:
(1) It is demanded by some sudden or intense sensory stimulus or
insistent idea, or (2) it follows interest, or (3) it is compelled by
the will. If it comes in the first way, as from a thunderclap or a flash
of light, or from the persistent attempt of some unsought idea to secure
entrance into the mind, it is called _involuntary_ attention. This form
of attention is of so li