«N AERIAL NAVIGATION. jfij 



William Chapman, civil engineer in Newcastle, I find that 

 SO drops of the oil of tar raised eight hundred weight to 

 the height of -23 inches; hence a one horse power may con- 

 sume from 10 to 12 pounds prr hour, and the engine itself less weighty, 

 need not exceed 50 pounds weight. I am informed by Mr. 

 Chapman, that this engine was exhibited in a working state 

 to Mr. Rennie, Mr. Edmund Cartwright, and several other 

 gentlemen, capable of appreciating its powers ; but that it but more ex* 

 was given up in consequence of the expense attending its 1 pensive ' 

 consumption being about 8 times greater than that of a steam 

 engine of the same force. 



Probably a much cheaper engine of this sort might be Combiutionof 

 produced by a gas-light apparatus, and by firing the inflam- ^ r flammable 

 mable air generated, with a due portion of common air, 

 under a piston. Upon some of these principles it is per- 

 fectly cJear, that force can be obtained by a much lighter 

 apparatus than the muscles of animals or birds, and there- 

 fore in such proportion may aerial vehicles be loaded with 

 inactive matter. Even the expansion steam engine doing 

 the werk of six men, and only weighing equal to one, will 

 -as readily raise five men into the air, as Mr. Degen can 

 elevate himself by his own exertions; but by increasing the 

 magnitude of the engine 10, 50, or 500 men may equally 

 well be conveyed; and convenience alone, regulated by the 

 strength and size of materials, will point out the limit for 

 the size of vessels in aerial navigation. 



Having rendered the accomplishment of this object pro- Principles of 

 bable upon the general view of the subject, I shall proceed the art * 

 to point out the principles of the art itself. For the sake Flight of a bird. 

 of perspicuity I shall, in the first instance, analyze the most 

 simple action of the wing in birds, although it necessarily 

 supposes many previous steps. When large birds, that have 

 a considerable extent of wing compared with their weight, 

 huve acquired their full velocity, it may frequently be ob- 

 served, that they extend their wings, and without waving 

 them, continue to skim for some lime in a horizontal path. 

 Fig. 1, PI. V, represents a bird in this act. 



Let a b be a section of the plane of both wings opposing 

 the horizontal current of the air (created by its own motion) 

 which may be represented by the line c J, ami is the mea- 

 sure 



