The hypothesis, then, that the demand for the filling of the whole space without large gaps anywhere enters into competition with the tendency to mechanical balance, and that this tendency is, nevertheless, reconciled with that demand through the power of a central position to confer importance, would seem to fit the facts.  It is, of course, clear that neither ‘mechanical balance’ nor the balance of ‘central’ with ‘intrinsic’ importance have been yet accounted for on psychological grounds; it is sufficient at this point to have established the fact of some kind of balance between elements of different qualities, and to have demonstrated that this balance is at least not always to be translated into the ‘mechanical’ metaphor.

C.  Experiments on Movement.

In the preceding experiments the element of size was isolated, and it was sought to discover, in pleasing combinations of objects of different sizes, the presence of some kind of balance and the meaning of different tendencies of arrangement.  The relative value of the two objects was taken as determined on the assumption, supported by common sense, that under like conditions a large object is given more attention than a small one.  If the unequal objects seem to balance each other, then the only other condition in which they differ, their distance from the center, must be the cause of their balancing.  Thus the influence of relative position, being the only unknown quantity in this balance-equation, is easily made out.

The following experiments will deal with the as yet quite undetermined elements of suggested movement, perspective and intrinsic interest.  By combining objects expressing them, each with another simple object of the same size, another equation will be obtained in which there is only one unknown quantity, the sizes of the objects being equal and the influence of relative position being at least clearly indicated.

1.  Movement.

The experiments on suggestion of movement were made by C, O and P.  Suggestions of movement in pictures are of two kinds—­given by lines pointing in a direction which the eye of the spectator tends to follow, and by movement represented as about to take place and therefore interpreted as the product of internal energy.  Thus, the tapering of a pyramid would give the first kind of suggestion, the picture of a runner the second kind.  Translated into terms of experiment, this distinction would give two classes dealing with (A) the direction of a straight line as a whole, and (B) the expression of internal energy by a curve or part of a line.  In order to be able to change the direction of a straight line at a given point, a strip of tin two inches long was fastened by a pivot to the usual clasp which slipped up and down on the vertical black strip.  The tin strip could be moved about the pivot by black threads fastened to its perforated ends.  A strip of cardboard glued upon it would then take its direction.