Notes.—­(1) All quite unsatisfactory.  The arrangement difficult to apperceive as a whole.  Each picture taken by itself. (2) The tunnel closed doesn’t amount to much. (3) The significance of the tunnel gives it weight.  For F. 160, V. 148, and F. 180, V. 180, relation difficult. (4) Court closed gets weaker as gets farther from center. (5) At F. 100, begins to lose relation between pictures, as if one were in one room, one in another.

SUBJECT A.

F.                         V.
(1)     (2)     (3)     (4) squared   (5) squared
40     70      66     140      59     130
60     80      73     159      62     138
80    103      71     120      77     134
100    113      94     108      93     100
120    119      88      96      96      63
140    108      92      60,164  82      43
160     92     118      70     109      50
180    130     154      78     101      50

squaredSecond pair (Court).

Notes.—­(1) Difficult to apperceive together.  From F. 140, V. 108, depth is more strongly imagined. (3) Tunnel closed has not much value. (5) F. 80, V. 134, taken with reference both to frame and to the other picture—­must not be symmetrical nor too far out.

SUBJECT D.

F.                             V.
(1)          (2)          (3)
40          100          47            38
60           75          60            68
80          104          78            80
100          148, -12    104           120
120          159         166           160
140          182         152, 84, 78   168
160          193         184, -75      180
180          200        — 95, 190      190

Note.—­F. 100, V.-12; F. 140, V.-52; F. 160, V. -75:  they
must be close together when on the same side.

F.                   V.
(1)           (2)¹
Subject M.   40            55            50
60            56            74
80            64            84
100            86           102
120            93           111
140           124           130
160           134           146
180           144           178

¹Second pair (Court).

Note.—­(1) Quite impossible to take both together; necessary
to keep turning from one to the other to get perception of
depth together with both.

The subjects agree in remarking on the lack of interest of the closed tunnel, and the attractive power of the open tunnel, and notes which emphasize this accompany choices where the open tunnel is put uniformly nearer. (Cf. H, F. 180, V. 50; F. 80, V. 13; G, (2), (3), (4), (5); A, (3), and F. 140.) As a glance at the results shows that the open tunnel is placed on the whole nearer the center, we may conclude that these choices represent a mechanical balance, in which the open tunnel, or depth in the third dimension, is ‘heavier.’