170 STOEY OF EXPERIMENTS IN MECHANICAL FLIGHT. 



The work was commeuced in the beginiimg of 1 887 by the construc- 

 tion, at Allegheny, of a turntable of exceptional size, driven by a steam 

 engine, and this was used during three years in making the "Experi- 

 ments in Aerodynamics," which were published by the Smithsonian 

 Institution under that title in 1891. Nearly all the conclusions reached 

 were the result of direct experiment in an investigation which aimed to 

 take nothing on trust. Few of them were then familiar, though they 

 have since become so, and in this respect knowledge has advanced so 

 rapidly, that statements which were treated as paradoxical on my first 

 enunciation of them are now admitted truisms. 



It has taken me, indeed, but a few years to pass through the period 

 when the observer hears that his alleged observation was a mistake; 

 the period when he is told that if it were true, it would be useless; 

 and the period when he is told that it is undoubtedly true, but that it 

 has always been known. 



May I quote from the introduction to this book what was said in 1891 ? 



"I have now been engaged since the beginning of the year 1887 in 

 exiieriments on an extended scale for determining the possibilities of, 

 and the conditions for, transporting in the air a body whose specific 

 gravity is greater than that of the air, and I desire to repeat my con- 

 viction that the obstacles in its way are not such as have been thought; 

 that they lie more in such apparently secondary difi&culties, as those of 

 guiding the body so that it may move in the direction desired and 

 ascend or descend with safety, than in what may appear to be primary 

 difficulties, due to the air itself," and, I added, that in this field of 

 research I thought that we were, at that time (only six years since), 

 "in a relatively less advanced condition than the study of steam was 

 before the time of Newcomen." It was also stated that the most import- 

 ant inference from those experiments as a whole was that mechanical 

 flight was possible with engines we could then build, as one horsepower 

 rightly applied could sustain over 200 pounds in the air at a horizontal 

 velocity of somewhat over 60 feet a second. 



As this statement has been misconstrued, let me point out that it 

 refers to surfaces, used without guys or other adjuncts, which would 

 create friction; that the horsepower in question is that actually ex- 

 pended in the thrust, and that it is iiredicated only on a rigorously 

 horizontal flight. This implies a large deduction from the power in the 

 actual machine, where the brake horsepower of the engine, after a 

 requisite allowance for loss in transmission to the propellers and for 

 their slip on the air, will probably be reduced to from one-half to one- 

 quarter of its nominal amount; where there is great friction from the 

 enforced use of guys and other adjuncts; but, above all, where there is 

 no way to insure absolutely horizontal flight in free air. All these 

 things allowed for, however, since it seemed to me possible to provide 

 an engine which should give a horsepower for something like 10 pounds 

 of weight, there was still enough to justify the statement that we 



