THE CONQUEST OF THE AIR. 353 



necessary instruments. For landing on the water the ship is 

 provided with water anchors, consisting- of frames covered with 

 cloth. For landing- on dry land, ground anchors are supplied, 

 and under each gondola is placed an air cushion to reduce the 

 impact of the ground. As the gondolas are keel shaped the 

 impact on the water is negligible. 



The crew of such a ship consists of two trained conductors 

 or captains, one first officer or steersman, also able to conduct, 

 with three lieutenants, of whom one at least is an engineer ; two 

 sub-conductors in the second gondola, of whom one is an en- 

 gineer ; finally for each motor, two mechanics; a total of 12 

 persons. 



The invention of the present day aeroplane is due to a German 

 the engineer Otto Lilienthal, who shared with Zeppelin the mis- 

 fortunes of the proverbial prophet. To Lilienthal is due the 

 arched sustaining surface, and his investigations on the same- 

 translated into many languages— still form the basis of present 

 day designs. He also invented the glide flight, i.e. the method 

 of learning how to sustain oneself in air ; and finally, it was 

 Lilienthal who was the first person that ever proved that flying 

 was not an impossible thing. 



The day, says the famous French aeronaut Ferber, on which 

 Lilienthal flew for the first time over a distance of fifteen metres, 

 may be considered the dawn of the era of human flight. 



_ The brothers Wright in America were also disciples of 

 Lilienthal, and when the latter was unfortunately killed in 1896, 

 Wilbur W^right took up his work. The admiration of the brothers 

 Wright for Lilienthal was admirably expressed by Orville Wright 

 during his stay in Berlin a year ago, and when '^ Ferber was last 

 at Berlin, he went out to Lilienthal's grave and deposited a 

 wreath with the inscription : — 



" LE CAPITAINE FERBER, 

 A SON MAITRE LILIENTHAL." 



It is not my intention to give a description of Lilienthal's and 

 the Wrights' earlier experiments. Both built man-carrying 

 gliders, with which they slided down slopes of hills on the top of 

 an opposing wind which acted as an inclined plane. 



Let us see how it is at all possible for a surface to sustain itself 

 in air. If we take a sheet of paper and move it rapidly down- 

 wards, the sheet being horizontal, we experience an upward 

 force. As the air underneath the paper has to be set in motion, 

 work has to be done. In other words, by the movement of the 

 paper the resisting air causes an upward force. An upward force 

 is also produced if the air is brought under the sheet of paper, 

 which is held stationary, and if the upward force is equal to the 

 weight of the paper, the latter will float. 



It might now appear that we ought to be able to sustain 

 matter heavier than air if we employed surfaces which were 

 moved rapidly downwards flatways on. Unfortunately, these sur- 

 faces cannot be innumerable, so that they would have to be moved 

 upwards in some collapsible state in order to become always avail- 

 able. Such apparatus have been built, but their efficiency is 



