of which was given at the beginning of each series by a momentary
illumination of the scale. In the darkness which followed the observer
brought the direction of sight, with open eyes, as satisfactorily as
might be into the plane of the horizontal, when, upon a simple signal,
the perforated scale was instantly and noiselessly illuminated by the
pressure of an electrical button, and the location of the point of
regard was read off the vertical scale by the observer himself, in
terms of its distance from the fixed point of origin described above.
The individual and general averages for this set of experiments are
given in the following table:


TABLE III.

Observer. Constant Error. Average Deviation. Mean Variation.
_A_ (50) + 7.75 20.07 19.45
_C_ " + 14.41 25.05 2.94
_D_ " + 14.42 34.54 29.16
_E_ " +108.97 108.97 23.13
_F_ " - 5.12 23.00 2.02
_G_ " + 20.72 34.80 10.23
_H_ " + 35.07 53.60 33.95
_I_ " + 25.52 30.68 22.49
_K_ " - 8.50 40.65 21.07

Average: + 23.69 41.26 17.16


The point at which the eyes rest when seeking the plane of the horizon
in total darkness is above its actual position, the positive