ngs, or effectually
calls forth the powers of the mind."

Though you know all this, you are in ignorance still. Truly a savage
might profess the art of agriculture in this fashion; for all this is
only as if one were to say that the conditions of success in farming
were to be where there were no earthquakes or avalanches, that is, to be
quiet; to have the ground cleared of trees, that is, to have the mind
free from cares and the shadows of sorrows; to have neither too much nor
too little sunshine and rain, that is, to be properly fed; and to have
good seed to put into the ground, that is, to engage the mind with a
topic which it will expand and reproduce. After all these things have
been secured, it is only a sort of barbaric husbandry that we have
practised. The common and rude experience of men, laboring without
thinking about their labor, teaches these things, and the very
beginnings of the art and science of Intellectual Economy come beyond
and after these.

What shall we say of those moods which every student passes through,
which turn and return upon the mind, irresistible and mysterious? What
are the causes of those strange and delightful exaltations of mind in
which thought runs like a clock when the pendulum is off, and crowds a
week of existence into an hour of time? Whence are those dull days which
come so unexpectedly, and sometimes lead a troop of dull followers, to
interrupt our life's work for a week at a time? Where are we to search
for obstructions in the channels of the mind when ideas will not flow?
How is it that, after a period of clearness and activity in thought, the
brain grows indolent, and, without a feeling of illness, or even of
fatigue, work lags and stops? By what right is it that, at times, each
faculty in our possession seems to grow independent, and refuses to
return to its task at our call? What are the secret psychological
conditions which influence the mental powers as strangely as if there
were a goblin who had power to mesmerize Fancy and put it to sleep, to
lock up Imagination in a dreary den of commonplaces, to blindfold
Attention and make sport of his vain groping, and to send sober Reason
off on foolish errands, so that Mistress Soul has not a servant left?

Such variations of mental power, which we call moods of mind, are often
caused, doubtless, by ill-health, or by fatigue, or by some irregularity
of habit, or by anxiety of mind; but the experience of every student
will pr