is accompanied by a depression of the line of sight, decreased
convergence by an elevation of it. Here such freedom was permitted,
and though the fixed distance of the point of regard eliminated all
large fluctuations in convergence, yet all the secondary
characteristics of intense convergence were present. Those concerned
in the experiment report that the whole process of visual adjustment
had increased in difficulty, and that the sense of effort was
distinctly greater. To this sharp rise in the general sense of strain,
in coöperation with the absence of a corrective field of objects, I
attribute the large negative displacement of the subjective horizon in
this series of experiments.


III.


In the next set of experiments the room was made completely dark. The
method of experimentation was adapted to these new conditions by
substituting for the wooden screen one of black-surfaced cardboard,
which was perforated at vertical distances of five millimeters by
narrow horizontal slits and circular holes alternately, making a scale
which was distinctly readable at the distance of the observer.
Opposite the end of one of these slits an additional hole was punched,
constituting a fixed point from which distances were reckoned on the
scale. As the whole screen was movable vertically and the observer
knew that displacements were made from time to time, the succession of
judgments afforded no objective criterion of the range of variation in
the series of determinations, nor of the relation of any individual
reaction to the preceding. The method of experimentation was as
follows: The observer sat as before facing the screen, the direction