adjustments upon which the accuracy of the judgment depends. Secondly,
it enters as a source of constant error into the determination of the
subjective horizon, which is attracted toward this new objective
plane. In the third section of the table are given the results of
judgments made in the presence of such a plane but without conscious
reference to it.[2] The figures here are of intermediate value in the
case of the mean variation and of slightly greater value than the
first in that of the constant error. In other words, the introduction
of such a plane cannot be wholly overlooked, though it may be greatly
abstracted from.

[2] In the preceding experiments the cord was definitely to be taken
into account in making the judgment. The method of so doing was by
running the eye back and forth over the cord preliminary to
determining the location of the point.

The single cord was next replaced by a plane of blackened wood six
inches wide and extending from the observer to the vertical screen.
This strip was arranged in two ways: first, from the observer's chin
to the bottom of the screen, and secondly, from the feet of the
observer to a point on the screen a short distance below the plane of
the objective horizon. The individual and average results are given in
the following table:


TABLE XII.

Observer. Descending Plane. Ascending Plane.

_A._ (10) +18.80 18.80 5.24 +35.10 35.10 8.27