198 THE LANGLEY AERODROME. 



Reverting to the present models, they represent a machine whose 

 weight is about 30 pounds, one-fourth of which is contained in the 

 engine and machinery, which is of unexampled lightness. Within the 

 small body, seen in the photograph suspended under the main rod, is 

 contained everything for generating li (brake) horsepower, the total 

 weight of fire grate, boiler, and every accessory being less than 7 

 pounds. The engine, with its cylinders, pistons, and every moving 

 part, weighs 26 ounces. This puts in motion the propellers, which, 

 turning at a rate of between 800 and 1,200 revolutions per minute, 

 drives the aerodrome at a speed which varies greatly, according to the 

 inclination given to the motionless "wings." 



Mr. Langley, after a great many years of preliminarj'' experiment on 

 supporting surfaces, which he has described in his "Experiments in 

 aerodynamics," first made a remarkable, and to the engineer, most para- 

 doxical statement; namely, that in such aerial navigation as was there 

 shown to be possible, under certain definite conditions the power 

 required would in theory diminish indefinitely as the speed increased, 

 and that it would actually diminish in practice up to a certain limit. 



This statement, which has since been called "Langley's law," is 

 justified in practice, but the conditions which give this increase of 

 speed with decrease of power are limited by others which demand 

 that the flight should be made in safety and without that danger of 

 accident which might come in applying rigorously exact theoi'etical 

 conclusions without regard to the securit}^ of the flight. The actual 

 speed which was obtained, then, was under conditions where security 

 was chiefly sought. 



In the experiments which have hitherto been made, safety has accord- 

 ingly been the first consideration, and the "wings," or rather the 

 motionless supporting surfaces, have been given such an inclination 

 as to cause the speed to be limited to between 20 and 30 miles an hour. 

 The machine has actually traveled very much faster than this, but its 

 higher speeds have not been measured. 



The aerodrome was launched from a specialh' constructed house 

 boat on the Potomac in a secluded spot about 30 miles below Wash- 

 ington, and was supplied with water for a short course lest it should, 

 in its uncontrolled flight, go altogether out of reach, and lose itself in 

 the neighboring Virginia forests. The idea of making the flight over 

 water from a house boat or raft may appear obvious when once stated, 

 but like many simple results it was only reached after long experi- 

 ment with other methods, and its utilit}' has since been shown by its 

 employment by others. There was no other reason why it should not 

 fly for an indefinite time except the waste of water, which in the model 

 had no provision for its renewal by condensation. This aerodrome, 

 which is one of several which have flown considerable distances, per- 

 formed this first flight on May 6, 1896, at a private trial of which Dr. 



