The pleasing effect of the design at Seventh and Locust streets is largely due to appropriate use of the evolute spiral band.
By and by that flour-sack is going to evolute into an underskirt for me to wear under my dress when I go to school.
This point evidently lies upon the branch zM of the evolute in Fig. 23.
A curve which has a given curve as evolute is called an “involute” of the given curve.
These names are given to the curves because the end of a stretched thread unwound from the evolute will describe the involute.
The evolute of a curve is the curve which is the envelope of all its normals or the locus of all its centres of curvature.
The locus of the centres of curvature, or envelope of the normals, of a curve is called the “evolute.”