172 STORY OF EXPERIMENTS IN MECHANICAL FLIGHT. 



tbese to ascertain the laws of " balancing; " that is, of stability leading 

 to horizontal flight. Most of these models had two propellers, and it 

 was extremely difficult to build them light and strong enough. Some 

 of them had superposed wings; some of them curved and some plane 

 wings; in some the propellers were side by side; in others one propeller 

 was at the front and the other at the rear, and so every variety of treat- 

 ment was employed, but all were at first too heavy, and only those flew 

 successfully which had from 3 to 4 feet of sustaining surface to a pound 

 of weight, a proportion which is far greater than Nature employs in 

 the soaring bird, where in some cases less than half a foot of sustain- 

 ing surface is used to a pound. It had been shown in the "Experi- 

 ments in aerodynamics" that the center of pressure on an inclined 

 plane advancing was not at the center of figure, but much in front of 

 it, and this knowledge was at first nearly all I possessed in balancing 

 these early aerodromes. Even in the beginning, also, I met remarkable 

 difficulty in throwing them into the air, and devised numerous forms 

 of launching apparatus which were all failures, and it was necessary to 

 keep the construction on so small a scale that they could be cast from 

 the hand. 



The earliest actual flights with these were extremely irregular and 

 brief, lasting only from three to four seconds. They were made at 

 Allegheny in March, 1891, but these and all subsequent ones were so 

 erratic and so short that it was possible to learn very little from them. 

 Penaud states that he once obtained a flight of thirteen seconds. I 

 never got as much as this, but ordinarily little more than half as 

 much, and came to the conclusion that in order to learn the art of 

 mechanical flight it was necessary to have a model which wo aid keex3 

 in the air for at any rate a longer period than these, and move more 

 steadily, liubber twisted in the way that Penaud used it will practi- 

 cally give about 300 foot-pounds to a pound of weight, and at least as 

 much must be allowed for the weight of the frame on which the rubber 

 is ^trained. Twenty pounds of rubber and frame, then, would give 

 3,000 foot-pounds, or 1 horsepower for less than six seconds. A steam 

 engine havifig apparatus for condensing its steam, weighing in all 10 

 pounds, and carrying 10 pounds of fuel, would possess in this fuel, 

 supposing that but one-tenth of its theoretical capacity is utilized, 

 many thousand times the power of an equal weight of rubber, or at 

 least 1 horsei)ower for some hours. Provided the steam could be con- 

 densed and the water reused, then the advantage of the steam over 

 the spring motor was enormous, even in a model constructed only for 

 the purpose of study. But the construction of a steam-driven aero- 

 drome was too formidable a task to be undertaken lightly, and I exam- 

 ined the capacities of condensed air, carbonic-acid gas, of various 

 applications of electricity, whether in the primary or storage battery, 

 of hot- water engines, of inertia motors, of the gas engine, and of still 

 other material. The gas engine promised best of all in theory, but it 

 was not yet developed in a suitable form. The steam engine, as being 



