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.