490 Professor G. H. Bryan [Feb. 8, 



flight. There still remain the problems of starting off the ground 

 and landing safely again, which become more difficult as the size of 

 the machine is increased. Still more intricate is the question of balance 

 and stability. The very fluctuations of wind-velocity, from which 

 sailing birds may not improbably derive their supply of energy, vastly 

 increase the difficulty of artificial flight. Langley speaks of wind- 

 velocities suddenly rising to forty miles an hour, and equally suddenly 

 dropping to a dead calm. With such gusts to contend against, the 

 danger of a machine suddenly capsizing is a very serious one. Mr. 

 Wenham relates that, thirty years ago, a gliding model of his, which flew 

 well from a housetop, was dropjied by Glaisher in one of his balloon 

 ascents, but, after gliding twelve yards, it tripped and whirled over and 

 over till it reached the earth. 



Our knowledge of the conditions of balance and stability is 

 largely deduced from experiments in gliding from a height under 

 gravity. In 1864, Captain Le Bris constructed an " artificial alba- 

 tross," with which he is reported to have made successful glides up 

 to 600 feet ; but he broke his leg, and his funds became exhausted, so 

 that the experiments had to be discontinued. In recent times, great 

 advances in the art of gliding have been made by Lilienthal in 

 Germany, Pilcher in England, and Chanute and Herring in America. 

 The death of the two former, as the result of accidents with their 

 machines, will no doubt deter others from working on the same lines. 

 It is therefore desirable to notice in detail, the points of difference 

 between the methods adopted by Chanute and Herring, and those of 

 their less fortunate predecessors. 



Both Lilienthal and Pilcher used broad wings ; the first in his 

 later experiments using a machine with two superposed surfaces, and 

 the second always using single-surface machines. Both were depen- 

 dent entirely on the movements of their body for counteracting the 

 tendency to overturn, produced by gusts of wind ; and, under such 

 conditions, gliding was of necessity an art requiring considerable 

 gymnastic agility. 



Mr. Octave Chanute commenced his gliding experiments, in 1896, 

 by constructing an " albatross machine," based on the design of Le 

 Bris ; but the large size of the machine necessitated its being flown 

 from a properly constructed track, and glides could only be made 

 when the wind was blowing in a particular direction. He next tried 

 gliding with a machine of the Lilienthal type, but soon discontinued 

 his experiments in this direction, as he regarded such a machine as 

 dangerous and difficult of control; and he became convinced of the 

 necessity of devising an automatic arrangement by which the appa- 

 ratus should right itself when a gust of wind caused it to heel over. 



His first attempt in this direction was the construction of a 

 " ladder kite," formed with wings pivoted to a central frame, and held 

 in place by rubber springs. The kite flew very steadily, and was 

 used as the basis of a " multiple-winged machine," also with movable 



