Note:  Do not rely on this information. It is very old.


Cissoid, a curve of much interest in higher geometry. It may be drawn in the following manner: - A circle is described on a line A B as diameter; the tangent E B F is drawn touching the circle at B, and points C1, C2 ..., on this tangent are joined up to A. Such lines all cut the circle at, say, D1, D2 ..., and if on these lines AO1, AO2 ...., are marked equal to C1 D1, C2, D2 . . , the points O1 O2, ... will lie on the cissoid.