TRAVEL IN THE AIR 



313 



and land almost vertically by means of four large 

 revolving blades mounted over the plane. Sometimes 

 the large revolving blades do the work of both pro- 

 peller and wings. In some cases the blades are used 

 along with an ordinary plane. 



Inttmational News Photos 



FIG. 527. AUTOGYRO 



The autogyro differs from the helicopter in that 

 the blades are not power driven from the engine but 

 are set in motion by the wind currents created when 

 the plane moves forward. Figure 525 shows a pic- 

 ture of a helicopter while Figure 527 shows the auto- 

 gyro. 



Of what importance are the airplane and the dirigi- 

 ble in transportation? Transportation by air has de- 

 veloped to the point where one can travel by plane 

 to almost any point in Europe or the United States. 

 Air lines connect all important cities and maintain 

 a schedule almost as regular as that of the railroads 

 or steamship lines. 



There are today more than 30,000 miles of airlines 

 in this country that maintain regular schedules. There 

 are also some 22,000 miles of airlines that connect 

 this country with Cuba, Mexico, South America, and 



Paul's Photos 



FIG. 528. THE China Clipper 



Canada. These lines carry passengers, mail, and ex- 

 press. During 1935-1936 air mail service was opened 

 between the Philippine Islands and the United States 

 operating on about a five-day schedule each way. 

 Figure 528 shows a picture of the China Clipper, the 

 first ship in the service of this new line. 



In 1934 scheduled airplanes in the United States 

 carried more than a half million people an average 

 distance of four hundred miles, transported 3,500,000 

 pounds of air express and 8,000,000 pounds of mail. 



The U. S. Bureau of Air Commerce has established 

 one of the finest systems of airways to be found any- 

 where in the world. In their service to aviators fly- 

 ing these routes they provide : 



1) teletype service on the movement of planes and 

 on weather conditions ; 



2) rotating beacon lights at intervals of ten to 

 fifteen miles for night flying; 



3) landing fields every fifty miles to be used in 

 cases of emergency; 



4) radio beacons every twenty-five to one hundred 

 miles; 



5) radio landing beams at fields which enable 

 planes to land "blind" in fogs ; 



6) radio communication to planes which enable 

 the sending of emergency messages and weather con- 

 ditions to pilots. 



Figure 529 shows the network of airlines which 

 cover the United States. 



Dirigibles are coming into use for transoceanic 

 transportation of passengers and express. The Graf 

 Zeppelin and the Hindenburg, German owned ships, fly 

 to South America at frequent intervals and have re- 

 cently established a line to the United States. 



REFERENCES FOR FURTHER STUDY 

 Texts 



Caldwell and Curtis, Science for Today, Chap. 28 



Clement, Collister, and Thurston, Our Surroundings, Chap. 

 20 (part) 



Hunter and Whitman, Science in Our World of Progress, 

 Unit 9 



Lake, Harley, and Welton, Exploring the World of Science, 

 Chap. 25 (part) 



Pieper and Beauchamp, Everyday Problems in Science, Unit 

 17 



Powers, Neuner, and Bruner, Man's Control of His Environ- 

 ment, Chap. 19 



Van Buskirk and Smith, The Science of Everyday Life, Chap. 

 20 



Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 3 



Wood and Carpenter, Our Environment: How We Use and 

 Control It, Topic 11 C 



Special references 



Campion's Pictured Encyclopedia 

 Verrill, Aircraft Rook for Boys 

 Molter, Knights of the Air 



