90 OUR PHYSICAL WORLD 



by a propeller through the air, cutting it so as to force itself up 

 as well as forward. Third, just as a propeller drives a boat 

 through the water, so it was thought might a propeller blade, 

 rapidly turning, screw itself and the attached machine up into 

 the air; then possibly a second propeller could drive the machine 

 in the desired direction. 



Now Cayley not only tried the glider successfully, but he was 

 apparently the first to make a helicopter, as this last-named 

 device is called. Truly it was only a toy affair, but it contained 

 the germ of an idea from which much is yet anticipated. The 

 directions for making a simple flier on the principle of the heli- 

 copter are given in the Field and Laboratory Guide in Physical 

 Nature-Study, page 3 1 . Helicopters have recently been built and 

 flown with success, carrying both pilot and passenger. They 

 have this advantage over the aeroplane, that they can rise 

 straight up and do not need a large field from which to start or 

 on which to land. 



M. A. Penaud, a Frenchman, in 1865 built a toy on the 

 principle of a flying bird, and it worked, the first successful 

 machine of its type. Later (in 1874) he built another model, 

 a miniature aeroplane, the motive power of which was twisted 

 strands of rubber. This worked even better than his orthopter. 



Herbert Wenham, an Englishman, coined the word " aero- 

 plane" (1868) and applied it to the glider. He had the idea also 

 that such a glider could be forced to rise and carry a man if an 

 engine could be mounted on it. He was the first to suggest 

 that two planes mounted one above the other in an aeroplane 

 would have greater lifting power than the single plane. 



The first aeroplane actually to carry an engine and fly was 

 a model built by Stringfellow, the Australian. He was a skilful 

 mechanic, and his engines were exquisitely built. He and Henson 

 had worked together to plan such a flying machine, but it was 

 Stringfellow who actually completed the work. It was in 1845 

 that he finished his 8^-pound model, the engine and boiler making 

 up 5 pounds of this weight. This model was a monoplane, and 



