THE Science Museum, South Kensington, has just acquired through the generosity of Mr. P. A. Smith of Scarborough a small disc of silver about an inch in diameter bearing an engraved design for a flying machine which is remarkable in conception. The disc bears the initials ‘G.C.’ with the letter ‘R’ beneath and it is dated 1799. The reverse contains a diagram of forces relative to the design illustrated. There is little doubt that it is the work of Sir George Cayley, Bart. (1774–1857), who was the first to attempt to explain mathematically the fundamental principles of mechanical flight. The flying machine represented is a manually propelled (assisted) glider. It is a large monoplane, the plane being curved, with the operator sitting in a boat-shaped structure below and working by means of levers two large rectangular oars or paddles which were probably intended to function on the non-return valve principle by means of flaps. An interesting feature is the combined rudder and elevator arrangement which consists of surfaces fixed at right angles to one another, the whole, it appears, universally pivoted—a device which has been attributed to Alphonse Penaud at a much later date. Research is being undertaken to discover the full significance of the design, but the disc has been placed on exhibition.