intensities, and possibly also of significant objects, above and below
the horizon belt. Every brilliant object attracts the eye toward
itself; and the horizon beneath a low sun or moon will be found to be
located higher than in a clouded sky. The upper half of the ordinary
field of view--the clear sky--is undiversified and unimportant; the
lower half is full of objects and has significance. We should probably
be right in attributing to these characteristic differences a share in
the production of the negative error of judgment which appears in
judgments made in daylight. The introduction of such supplementary
stimuli appears to have little effect upon the regularity of the
series of judgments, the values of the mean variations being
relatively low: 17'.42 with light below, 17'.74 with it above.


IX.


In the final series of experiments the influence of limiting visual
planes upon the determination of the subjective horizon was taken up.
It had been noticed by Dr. Münsterberg in the course of travel in hill
country that a curious negative displacement of the subjective horizon
took place when one looked across a downward slope to a distant cliff,
the altitude (in relation to the observer's own standpoint) of
specific points on the wall of rock being largely overestimated.
Attributing the illusion to a reconstruction of the sensory data upon
an erroneous interpretation of the objective relations of the
temporary plane of the landscape, Dr. Münsterberg later made a series
of rough experiments by stretching an inclined cord from the eye
downward to a lower point on an opposite wall and estimating the
height above its termination of that point which appeared to be on a