576 MACHINES, WORK, AND ENERGY 



able to navigate the air, to fly as the birds do. Experimentors 

 realized the necessity of producing a motor of great power 

 with as little weight as possible. Before the end of the 

 last century, in 1896, Prof. Langley at Washington, D. C., 

 constructed a steam-driven flying machine which flew without 

 a passenger several times, once more than a half mile over 

 the Potomac River before its fuel supply was exhausted and 

 it fell of its own weight into the water. 1 All attempts to 

 produce a successful " heavier-than-air " flying machine failed 

 until the gasoline engine was highly perfected. Every other 



FIG. 362. The Langley aeroplane flying, May 28, 1914. 



type of motor has proved too heavy for the power it could 

 produce. Gasoline motors now used on aeroplanes are 

 marvels of lightness and power. Such engines usually weigh 

 but from 3 to 5 Ib. per horse-power. 



691.- Importance of the Gas Engine in Large Power Plants. 

 During recent years it has been shown that gas engines are 

 much more economical of fuel than are steam engines in 



1 It is an interesting fact that two attempts were made in 1904 to prove 

 that Langley's aeroplane could fly while carrying a pilot. Upon both occa- 

 sions, however, the machine plunged into the river as quickly as it was 

 launched. It is now known that the trouble lay partly in the inexperience 

 of the pilot. On May 28, 1914, Glenn Curtis, an experienced flyer, made a 

 successful flight with the Langley aeroplane which had rested for years in 

 the archives of the Smithsonian Institute and had been styled "Langley's 

 Folly" (Fig. 362). 



