THE CONQUEST OF TIME AND SPACE 



complete failure. It showed a tendency to rise, but its 

 lifting power was insufficient, for the weight of the engine 

 driving the propellers. It was evident, however, that if 

 the power of the engine could be sufficiently increased, 

 or, what amounts to the same thing, its weight sufficiently 

 lightened, a machine built on the aeroplane prin- 

 ciple could be made to fly. But at that time the lightest 

 type of engine was a crude, heavy machine, and for the 

 moment nothing more was attempted in producing a 

 mechanical flying-machine propelled by steam. 



Meanwhile the possibility of producing a dirigible 

 balloon was again brought into prominence by the sug- 

 gestion of two aeronauts, Scott and Martainville, to 

 change the shape of the envelope of the balloon. Hither- 

 to, all balloons had been made globular or pear-shaped — 

 shapes that offered great resisting surfaces to the atmos- 

 phere. Now it was proposed to make them in the form 

 of long, horizontal cylinders, with pointed ends, these 

 cigar-shaped, or boat-shaped balloons offering much 

 less resistance. But here, as in the case of the flying- 

 machine, engines that were sufficiently strong to work 

 the propellers were found to be too heavy for the balloon 

 to lift. Meanwhile the aeroplane idea was brought into 

 prominence from an unexpected quarter. 



Among the numerous observers in the middle of the 

 century who had noted the soaring power of birds, was 

 a French sea-captain named Le Bris. On his long 

 voyages he had studied the movements of the great 

 albatross, which, with wings rigidly distended, outsailed 

 the swiftest ship without any apparent exertion. Anxious 

 to study the wing-mechanism of this bird, the captain, 



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