ABSTRACT
We now consider parallels and involutes of a curve. A parallel is the locus of points lying a fixed distance along the normals to the curve (as in parallel lines), and an involute of a curve t H» W(£) is a curve of which t i-> w(£) is the evolute. Involutes are not unique. Any parallel to an involute is an involute, and any two involutes are parallel to one another. An involute is the locus of a point on a piece of string as the string is wrapped along the curve or unwrapped from the curve.
