level with the observing eye. He found an illusion present similar to
the case of an extended slope of country.

The first experiments of this group repeated those just described. The
previous mechanical conditions were varied only by the introduction of
a slender cord which was stretched from just below the eyes to the
bottom of the vertical screen. Full results were obtained from only
two observers, which are given in the following table:


TABLE XI.

Observer. Const. Err. Av. Dev. Mean Var. Exp. Conds.

_C_ (30) +123.92 123.92 11.94 Cord present and
_G_ (30) +66.47 66.47 15.56 consciously referred to.
_C_ (30) +126.90 126.90 6.31 Cord not present.
_G_ (30) +83.20 83.20 6.31
_C_ (30) +126.93 126.93 6.39 Cord present but not
_G_ (30) +86.63 86.63 9.40 consciously referred to.

Averages. I +95.19 95.19 13.75
" II +105.05 105.05 6.31
" III +106.78 106.78 7.89


The effect of introducing such an objective plane of reference is
twofold: the mean variation is increased, and the plane of the
subjective horizon is displaced downwards. First, then, it acts as a
simple factor of disturbance; it distracts from those habitual