_C_ (50) - 8.02 11.82 9.47 - 48.14 48.14 9.52
_F_ (50) + 78.88 78.88 2.89 + 25.54 25.54 1.98
_G_ (50) - 22.56 24.64 6.58 -101.20 101.20 7.39
_H_ (50) - 83.84 83.84 11.78 -230.20 230.20 11.88
_J_ (50) +315.64 315.64 18.16 +120.12 120.12 9.01
Average: + 55.96 102.96 9.78 -44.98 104.84 7.96

Horizontal Planes.
Observer. Const. Err. Av. Dev. Mean Var.
_C_ (50) - 27.86 27.86 9.58
_G_ (50) - 73.84 73.84 7.59
_J_ (50) +243.72 243.72 18.52


For every individual observer, the position of the disc on the screen
has been affected by each change in the direction of these visible
lines. In every case, also, its location when these boundaries lay in
a horizontal plane was intermediate between the other two. The
importance of such relations in the objects of the visual field as
factors in our ordinary determination of the subjective horizon is
made evident by these experimental results. They become construction
lines having assumed permanence in the world of visual-motor
experience. The conception of unchanging spatial relations in the
fundamental lines of perspective vision receives constant
reinforcement from the facts of daily experience. The influence of the
above-described changes in experimental conditions is mediated through
their effect upon the location of the focus of the limiting and
perspective lines of vision. As the plane of the upper boundaries of
the enclosing walls was elevated and depressed the intersection of the
two systems of lines was correspondingly raised and lowered, and in