British mathematician and military engineer who laid the groundwork for modern ordnance (field-artillery) theory and practice with his New Principles of Gunnery (1742), which invalidated old suppositions about the nature and action of gunpowder and the flight of projectiles and formed the basis of all later scientific studies in these fields. His invention of the ballistic pendulum, a device allowing the determination of the momentum of a projectile suddenly halted in its flight, enabled gunners for the first time to measure with considerable exactness the muzzle velocities of projectiles delivered by their pieces.