A note on the Blackburn pendulum

The invention of the ‘‘Y-suspended’’ pendulum in 1815 by James Dean and analyzed in the same year by Nathaniel Bowditch has been discussed by Crowell [Am. J. Phys. 49, 452–454 (1981)]. It was reinvented by Hugh Blackburn in approximately 1844 while he was a student at Cambridge and is frequently referred to as the ‘‘Blackburn pendulum’’ in the literature. The history of this device for demonstrating harmonic motion is traced. Blackburn was professor of mathematics at the University of Glasgow for 30 years, and a biographical sketch of him is included.