been
hung in such a way as to allow for this illusion. Whenever a picture
was to be put up between two others of considerable difference of
size, or between a door (large) and a window (small), it had actually
been hung a little nearer to the smaller--toward the small picture or
toward the window--and not in the true middle.

It is probable that interesting applications of this illusion may be
discovered in aesthetics. For wherever in drawing or painting it is
wished to indicate to the observer that a point is midway between two
lines of different lengths, we should find that the artist, in order
to produce this effect most adequately, deviates a little from the
true middle. So in architecture, the effect of a contrast of masses
often depends upon the sense of bilateral balance, symmetry, or
equality, in which this visual error would naturally come into play.
Indeed, it is only necessary to recall to mind that one of the
principal laws of aesthetic effect in the matter of right line
proportion is the relation of "one to one," as it is called, or equal
division, to see the wide sphere of application of this illusion. In
all such cases the mistake of judgment would have to be allowed for if
masses of unequal size lie at the ends of the line which is to be
divided.

IV. _The Accuracy of Memory._--Another investigation may be cited to
illustrate quite a different department. It aimed to find out
something about the rate at which memory fades with the lapse of time.
Messrs. W., S., and B.[7] began by formulating the different ways in
which tests may be made on individuals to see how accurate their
memories are after different periods of time. They found that three
different tests might be employed, and called them "methods" of
investigating memory. These are, first, the method of Reproduction.
The individual is asked to reproduce, as in an oral or written
examination, what he remembers of something told him a certain time
before. This is the ordinary method of the schools and colleges, of
civil-service examinations, etc. Second, the method of Identification,
which calls upon the person to identify a thing, sentence, report,
etc., a second or third time, as being the same in all respects as
that which he experienced the first time it appeared. Third, the
method of Selection, in which we show to the person a number of
things, sentences, reports, descriptions of objects, etc., and require
him to select from them the ones whi