well-known principles of orthodox psychology. Self-torture or hard
driving is not nearly as helpful as a strong inner purpose to keep
the chosen subject in the real center of conscious thought.

The subject that comes to mind when there is a lull in the outside
demands on the attention, or one that is insistent on taking
possession of the mind, even when other matters are objectively
more in evidence,--that subject is the one that holds the center
of the inner attention. That is the controlling idea or purpose.
Ordinarily, it is some diversion; occasionally, the haunting
bugbear of some unfinished work or obligation. If the mind is
dominated by such ideas or any other than the real problem in
hand, the individual is seriously handicapped.

When a problem of machine design is undertaken, the mind must make
it the real center of attraction. To one having an average
endowment for such work, this is not a difficult task, but to get
the best results it should be rightly undertaken.

Repeated Thinking.

A chosen subject is brought, with some lasting effect, to the
center of attention by repeatedly bringing it into the mind at the
moments of lull in the pressure of other affairs. The astronomers
wait for the moment of best seeing, and the designer must wait for
the actual psychological moment.

The best seeing condition for the astronomer is due in a small
measure to his own physical condition, and in a large measure to
atmospheric conditions, but the most opportune time for
clear-headed vision of the designer is due mostly to his own
physical and mental condition.

Probably no two men have their minds equally affected by their
environment or their physical condition, but the fact that there
is a most favorable time and condition for such thought and work
should continually be borne in mind. Without this a man with
natural endowment may try his wings at flight at an inopportune
time, and if he fails he may be firmly convinced that he was never
made for flying.

This undoubtedly applies equally well to other kinds of work. It
may not be strictly true of a perfectly normal man (if there be
such a creature), but it is truly applicable to many workers in
this and similar kinds of work.

This phase is mentioned in order to make clear, not only how a
designer should work, but the thought that should be kept
uppermost in the mind of one who is trying to do this work.

The physical condition is more or less dependent