This gives the subject another opportunity to stop it at what he judges to be the exact middle of the line, and so on.

The accompanying figure (Fig.

7) shows the entire arrangement.
[Footnote 5: This and the following letters in parentheses refer to Fig.

7] [Illustration: FIG.

7] A great many experiments performed in this way, with the squares set both vertically and horizontally, and with several persons, brought a striking and very uniform result.