18 Centimeters.

A B C D E
less = gr. less = gr. less = gr. less = gr. less = gr.
R. (a) 2 0 23 0 0 25 4 4 17 3 1 21 0 1 24
(b) 3 1 21 1 0 24 5 3 17 1 6 18 0 2 23
F. (a) 1 4 20 3 0 22 8 6 11 0 5 20 2 0 23
(b) 2 3 20 2 1 22 6 7 12 1 4 20 0 3 22
K. (a) 4 2 19 4 0 21 2 7 16 0 7 18 0 0 25
(b) 1 0 24 2 6 17 8 0 17 2 6 17 1 0 24
-------- -------- -------- -------- --------
13 10 127 12 7 131 33 27 90 7 29 114 3 6 141

TABLES IV.-VIII.

The first line in column _A_ (Table IV.) signifies that out of 10
judgments, comparing an open space 4 cm., total weight 20 gr., with a
filled space of 4 points, total weight also 20 gr., the filled space
was judged less 7 times, equal 2 times, and greater once.


III.


The results of the investigation, thus far, point to the conclusion
that short filled spaces are underestimated, that long spaces are
overestimated, and that between the two there lies what might be
called an 'indifference zone.' This unexpected outcome explains, I
think, the divergent opinions of the earlier investigators of this