IV.

The influence of this factor is also exhibited when judgments made with both eyes are compared with those made under conditions of monocular vision.  The latter experiments were carried on in alternate series with those already described.  The figures are given in the following tables: 

TABLE VI.

  JUDGMENTS MADE IN DIFFUSED LIGHT.

Observer.  Constant Error.  Average Deviation.  Mean Variation. A (50) — 28.46 29.04 8.87 C " + 7.54 14.86 8.01 D " + 39.32 43.28 13.83 E " + 50.46 65.26 9.86 F " + 62.30 62.30 1.60 G " 0.00 45.28 9.66 H " + 22.92 79.12 5.07 I " + 14.36 51.96 8.02 K " + 9.26 38.10 9.55 L " — 61.10 61.10 6.36 Average:  + 11.66 49.03 8.18

TABLE VII.

  JUDGMENTS IN ILLUMINATED POINT.

Observer.  Constant Error.  Average Deviation.  Mean Variation. A (50) — 38.42 51.96 32.64 C (30) — 29.03 41.23 35.75 D (20) — 30.87 34.07 17.24 E (50) + 65.30 75.86 29.98 F " + 50.74 50.74 5.89 G " + 66.38 88.10 44.98 H " + 65.40 80.76 42.93 I " — 0.02 80.22 47.53 K " — 44.60 52.56 32.93 L " — 71.06 73.30 31.86 Average:  — 3.38 62.88 32.17

The plane of vision in judgments made with the right eye alone is deflected upward from the true horizon to a greater degree than it is depressed below it in those made with binocular vision, the respective values of the constant errors being -7’.70 and +11’.66, a difference of 19’.36.  When the field of vision is darkened except for the single illuminated disc, a similar reversion of sign takes place in the constant error.  With binocular vision the plane of the subjective horizon is deflected downward through 36’.62 of arc; with monocular vision it is elevated 3’.38, a difference of 40’.00, or greater than in the case of judgments made in the lighted room by 20’.64.  This increase is to be expected in consequence of the elimination of those corrective criteria which the figured visual