Logarithmic Spiral Sector
In this illustration, "the driven surface of the slide coincides with the tangent to the spiral, the line of centres being from o through c to infinity and perpendicular to the direction of motion of the slide.""
Peter Schwamb, S.B. And Allyne L. Merrill, S.B. Elements of Mechanism (New York, NY: John Wiley & Sons, Inc., 1904)
Courtesy the private collection of Roy Winkelman