cloth.  On these strips figures glued to small clamps or clasps could be slipped up or down; this arrangement of cooerdinates made it possible to place a figure in any spot of the whole surface without bringing the hands into the field of view.  The experiments were made in a dark room, in which the apparatus was lighted by an electric globe veiled by white paper and hung above and behind the head of the subject, so as not to be seen by him and to cast no shadow:  in this soft light of course the black movable strips disappeared against the black background.  A gray paper frame an inch and a half wide was fitted to the black rectangle to throw it up against the black depths of the dark room—­thus giving in all details the background of a picture to be composed.

The differences in method between the two sets of experiments were fundamental.  In Dr. Pierce’s experiments the figures were pulled from one side to the other of the half-square in question, and the subject was asked to stop them where he liked; in those of the writer the subject himself moved the slides back and forth until a position was found aesthetically satisfactory.  The subject was never asked, Does this balance?  He was indeed requested to abstract from the idea of balance, but to choose that position which was the most immediately pleasing for its own sake, and so far as possible detached from associations.

I have said that Dr. Pierce intentionally accentuated the center.  The conditions of pictorial composition suggest in general the center only by the rectangular frame.  Most of my experiments were, therefore, made without any middle line; some were repeated with a middle line of fine white silk thread, for the purpose of ascertaining the effect of the enhanced suggestion of the middle line.

But the chief difference came in the different treatment of results.  Dr. Pierce took averages, whereas the present writer has interpreted individual results.  Now, suppose that one tendency led the subject to place the slide at 50 and another to place it at 130 mm. from the center.  The average of a large number of such choices would be 90—­a position very probably disagreeable in every way.  For such an investigation it was evident that interpretation of individual results was the only method possible, except where it could be conclusively shown that the subjects took one and only one point of view.  They were always encouraged to make a second choice if they wished to do so, as it often happened that one would say:  ’I like both of these ways very much.’  Of course, individual testimony would be of the highest importance, and a general grouping into classes and indication of the majority tendency would be the only way to treat the results statistically.  And indeed in carrying out the experiments this caution was found absolutely necessary.  In all but one or two of the sections, the taking of averages would have made the numerical results absolutely unintelligible.  Only the careful study of the individual case, comparison of various experiments on the same person to find personal tendencies, and comparison of the different tendencies, could give valuable results for the theory of symmetry.