96 OUR PHYSICAL WORLD 



so as to deliver air to the engine cylinders at normal sea- 

 level pressure. The aviator wears electrically heated clothing 

 and a mask which is connected with an oxygen tank so he may 

 be supplied with the necessary oxygen for respiration. In the 

 flight of Mr. MacReady, when in 1920 he attained a height of 

 36,020 feet, the valves of his oxygen apparatus failed to work 

 properly as they rose into the very thin air. The aviator lost 

 consciousness; the machine, out of control, fell, but, luckily, 

 MacReady regained sufficient consciousness at a height of 

 some 2,000 feet to get control of his machine and make a 

 landing. 



In the Pulitzer trophy race at St. Louis, Missouri, in 1923 an 

 American, Lieutenant A. J. Williams, won, driving a blue Curtiss 

 navy plane over the 12 5-mile course at a speed of 243.67 miles 

 an hour. On a short, straight course a speed of nearly 400 

 miles an hour has been achieved. Already the Atlantic has 

 been crossed in a single flight. Furthermore, the aeroplane has 

 been developed to the point where it is commercially valuable. 

 Regular mail routes are now established both in Europe and in 

 this country. New York mail is carried to San Francisco, and 

 the Pacific Coast mail back to New York. New York, Cleve- 

 land, Chicago, Minneapolis, St. Louis, Omaha, San Francisco, 

 Portland, are all connected now by the regular air-mail routes. 

 Regular passenger service is established. The time from Paris 

 to London is two hours. The passenger rides in a coach that is 

 quite as stable, comfortable, and luxurious as a Pullman car. 



A simple but very effective type of aeroplane is made as 

 follows: Cut a f-inch square strip of white pine 22 inches long 

 (or use a piece of bamboo f inch wide). This strip should be 

 straight-grained and free from knots, for it serves as the back- 

 bone of the machine and must bear the strain of the twisted 

 rubber bands that serve to run the propeller. 



Cut a strip of tin 4 inches long and f inch wide. Bend it 

 2 inches from one end into a sharp V. Holding it with the long 

 arm to the left, bend this long arm i inch from its end so that the 



