The diagonal being an unsupported line naturally suggests instability, change, motion, transit. Its purpose frequently is to connect the stabler forms of the composition or lead therefrom.

The curvilinear line is the basis of variety and graceful movement. As an adjunct, it assists the sequence of parts. In the latter capacity it is of great importance to the composer. It is of course the basis of the circle as well as the important notion of circular construction and observation.

Given the subject and means of expression the final labor is the restraint or enforcement of parts in the degree of their importance. This requires ingenuity and knowledge and frequently demands a reconstruction of the original scheme.