are their components, that is to say, the elementary
sensations, which must be combined into groups to reach our
consciousness."

Maudsley says: "Examine closely and without bias the ordinary mental
operations of daily life, and you will find that consciousness has not
one-tenth part of the function therein which it is commonly assumed
to have. In every conscious state there are at work conscious,
sub-conscious, and infra-conscious energies, the last as indispensable as
the first."

Oliver Wendall Holmes said: "There are thoughts that never emerge into
consciousness, which yet make their influence felt among the perceptible
mental currents, just as the unseen planets sway the movements of those
that are watched and mapped by the astronomer."

Many other writers have given us examples and instances of the operation
of the out-of-consciousness planes of thought. One has written that when
the solution of a problem he had long vainly dealt with, flashed across
his mind, he trembled as if in the presence of another being who had
communicated a secret to him. All of us have tried to remember a name
or similar thing without success, and have then dismissed the matter from
our minds, only to have the missing name or thought suddenly presented to
our conscious mind a few minutes, or hours, afterwards. Something in our
mind was at work hunting up the missing word, and when it found it it
presented it to us.

A writer has mentioned what he called "unconscious rumination," which
happened to him when he read books presenting new points of view
essentially opposed to his previous opinions. After days, weeks, or
months, he found that to his great astonishment the old opinions were
entirely rearranged, and new ones lodged there. Many examples of this
unconscious mental digestion and assimilation are mentioned in the books
on the subject written during the past few years.

It is related of Sir W. R. Hamilton that he discovered quarternions one
day while walking with his wife in the observatory at Dublin. He relates
that he suddenly felt "the galvanic circle of thought" close, and the
sparks that fell from it was the fundamental mathematical relations of
his problem, which is now an important law in mathematics.

Dr. Thompson has written: "At times I have had a feeling of the
uselessness of all voluntary effort, and also that the matter was working
itself clear in my mind. It has many times seemed to me that I was really
a passive