In 1850 a clockmaker and skillful workman, Jullien by name, exhibited in the Hippodrome, at Paris, a torpedo-shaped model balloon of gold-beater’s skin, provided with a screw propeller at either side of its bow, and a double rudder at its stern. It measured 23 feet in length and weighed 1,100 grammes complete. The propellers were actuated by spring power, and proved able to drive the tiny vessel against a moderate wind. The most suitable form for the bag was determined by towing models through water.