The point selected by the subject as the middle is regularly too far toward the smaller square.

Not a little, indeed, but a very appreciable amount.

The amount of the displacement, or, roughly speaking, of the illusion, increases as the larger square is made larger and the smaller one smaller; or, put in a sentence, the amount varies directly with the ratio of the smaller to the larger square side.
Finding such an unmistakable illusion by this method, Mr.B.thought that if it could be tested by an appeal to people generally, it would be of great gain.

It occurred to him that the way to do this would be to reverse the conditions of the experiment in the following way: He prepared the figures given in Plate I, in which the two squares are made of suitable relative size, a line is drawn between them, and a point on the line is plainly marked.

This he had printed in a weekly journal, and asked the readers of the journal to get their friends, after merely looking at the figure (i.e., without knowing the result to be expected), to say--as the reader may now do before reading further--whether the point on the line (Plate I) is in the middle or not; and if not, in which direction from the true middle it lies.