the eye to come to rest under determinate mechanical conditions of
equilibrium of muscular strain.

The relation of the successive judgments of a series to the
reinstatement of specific eye-strains and to the presence of an error
of constant tendency becomes clearer when the distribution of those
series which show progression is analyzed simultaneously with
reference to conditions of light and darkness and to binocular and
monocular vision respectively. Their quantitative relations are
presented in the following table:


TABLE IV.

Illumination. Per Cent. Showing Progress. Binocular. Monocular.

In light. 7.6 % 50 % 50 %
In darkness. 18.3 34.2 65.8


Among judgments made in daylight those series which present
progression are equally distributed between binocular and monocular
vision. When, however, the determinations are of a luminous point in
an otherwise dark field, the preponderance in monocular vision of the
tendency to a progression becomes pronounced. That this is not a
progressive rectification of the judgment, is made evident by the
distribution of the directions of change in the several experimental
conditions shown in the following table: