It is well known to ‘curve-stitchers’ that, if equally spaced points around a circle are numbered 1, 2, 3,..., n (and then repeated cyclically), then the chords joining 1 to 2, 2 to 4, 3 to 6, ..., n to 2n envelop a cardioid. (See [1], p. 41, §16, where the cardioid is described as “the caustic of a circle with respect to a point on its circumference”.) Correspondence with E. H. Lockwood has led to a rather unexpected result from this envelope.