The Three Secretaries 227 



change in five years. Incredulity has given way, interest 

 has been aroused in the scientific question, a sound basis has 

 been furnished for experiment, and practical results are being 

 evolved by many workers. Much remains to be discovered 

 concerning curved surfaces, with which alone practical flight 

 is likely to be achieved, but when this is accomplished it is 

 probable, in my judgment, that the beginning of the solution 

 will be acknowledged to date back to the publication of Doctor 

 Langley's book, and that he will be distinguished as Secretary 

 Henry is now with regard to the development of electrical 

 appliances." 



In the brief interval between the date of the letter just 

 quoted and the sending of this sketch to the printer, an aero- 

 drome, constructed by Mr. Langley, has made two successful 

 flights, each to a distance of rather more than half a mile, 

 practically demonstrating the correctness of the principles 

 which it has been seen were generally accepted, on theoretical 

 grounds, as soon as they were made public.^ 



1 A description of these flights, which took wheels ceased turning, and the machine, de- 

 place on May 6, 1896, was communicated to prived of the aid of its propellers, to my sur- 

 the Coviptes Rendus of the French Academy prise, did not fall, but settled down gently, 

 of Sciences, by Professor Alexander Graham and without the least shock, and was imme- 

 Bell, who was an eye witness, and an Eng- diately ready for another trial, 

 lish translation of the same is contained in "In the second trial, which followed di- 

 Natiire, Volume Liv, page 80. rectly, it repeated in nearly every respect the 



Professor Bell states that two ascensions actions of the first, except that the direction 



were made by the aerodrome which was built of its course was different. It ascended 



almostentirely of metal, and driven by a steam again in the face of the wind. I estimated 



engineofextraordinary lightness, the absolute that the actual length of flight on each occa- 



weight of the aerodrome, including the engine sion was slightly over three thousand feet, 



and all its appurtenances, being about twenty- It is at least safe to say that each exceeded 



five pounds, and the method of propulsion by half an English mile." 



aerial propellers, without any gas or other aid He continues : " I cannot but add that it 



for lifting it in the air, except its own internal seems to me that no one who was present on 



energy. this interesting occasion could have failed to 



"On the occasion referred to," says Pro- recognize that the practicability of mechanical 



fessor Bell, "the aerodrome, at a given sig- flight had been demonstrated." 



nal, started from a platform about twenty A third and still longer flight was made on 



feet above the water, and rose at first directly November 28, 1896, with another machine 



in the face of the wind, moving at all times built of steel like the first, and driven like 



with remarkable steadiness, and continually that by propellers actuated by a steam engine 



ascending until its steam was exhausted, of between one and two horse power, making 



when, at a height I judged to be between a horizontal flight of over three-quarters of a 



eighty and one hundred feet in the air, the mile, and descending in safety. 



