AERONAUTICS. 



211 



tlieir interior ; that those cavities contain heated air, and that 

 this heated air in some mysterious manner contributes to, if 

 it does not actually produce, flight. No argument could be 

 more fallacious. Many admirable fliers, such as the bats, 

 have no air-cells ; while many birds, the apteryx for example, 

 and several animals never intended to fly, such as the orang- 

 outang and a large number of fishes, are provided with them. 

 It may therefore be reasonably concluded that flight is in no 

 way connected with air-cells, and the best proof that can be 

 adduced is to be found in the fact that it can be performed 

 to perfection in their absence. 



The Inclined Plane. — The modern school of flying is in 

 some respects quite as irrational as the ballooning school. 



The favourite idea with most is the wedging forward of a 

 rigid inclined plane upon the air by means of a " vis a fergoJ' 



The inclined plane may be made to advance in a horizontal 

 line, or made to rotate in the form of a screw. Both plans 

 have their adherents. The one recommends a large support- 

 ing area extending on either side of the weight to be elevated; 

 the surface of the supporting area making a very slight angle 

 with the horizon, and the whole being wedged forward by the 

 action of vertical screw propellers. This was the plan sug- . 

 gested by Henson and Stringfellow. 



Mr. Henson designed his aerostat in 1843. The chief 

 feature of the invention was the very great expanse of its 

 sustaining planes, which were larger in proportion to the 

 weight it had to carry than those of many birds. The 

 machine advanced tvith its front edge a little raised, the 

 effect of which was to present its under surface to the air 

 over which it passed, the resistance of which, acting upon it 

 like a strong wind on the sails of a windmill, prevented the 

 descent of the machine and its burden. The sustaining of 

 the whole, therefore, depended upon the speed at which it 

 travelled through the air, and the angle at which its under 

 surface impinged on the air in its front. , . . The machine, 

 fully prepared for flight, was started from the top of an 

 inclined plane, in descending which it attained a velocity 

 necessary to sustain it in its further progress. That velocity 

 would be gradually destroyed by the resistance of the air to 

 forward flight; it was, therefore, the oflice of the steam- 



