Paper, 'Experiments about the motions of pendulums in vacuo' by William Derham Experiments on pendulums in air tight vacuums with the desire to know, whether there be any, or what difference, between the vibration of pendulums in vacuo, and the air. Subject: Aerodynamics Published in Philosophical Transactions as 'Experiments about the motion pendulums in vacuo' Read to the Royal Society on '25 October 1704 or 7 February' 1704