170 ON AERIAL NAVIGATION. 



in consequence of its being supported by bracings to the 

 line of its axis, and at a considerable distance from each 

 other; in fact the bracings form the hinge. 

 Means of The means of communicating motion to any surfaces 



TO^lon'^'*^**"'* """"St vary so much, according to tlie general structure of the 

 whole machine, Hiat I shall only observe at present, that 

 where human muscular action is employed, the movement 

 should be similar to the mode of pulling oars; from which 

 any other required motion may be derived; the foot board 

 in front enables a man to exert his full force in this posi- 

 tion. The wings I have described were wafted in this man- 

 ner ; and when they lifted with a power of 9 stone, not half 

 of the blow, which a man's strength could have given, was 

 exerted, in consequence of the velocity required being 

 greater than convenient under the circumstances. Had 

 these wings been intended for elevating the person who 

 ■worked them, they should have contained from 100 to 150 

 square feet each ; but they were constructed for the purpose 

 of an experiment relative to tlie propelling power only. 

 Importance of Avoiding direct resistance is the next general principle, 

 avoiding resist that it is necessary to discuss. Let it be remembered as a 

 ^^^^' maxim in the art of aerial navigation, that every pound of 



direct resistance, that is done away, will support 30 pounds 

 of additional weight without any additional power. The 

 Man equal to figure of a man seems but ill calculated to pass with ease 

 the crow in through the air, yet 1 hope to prove him to the full as well 

 made in this respect as the crow, which has hitherto been our 

 standard of comparison, paradoxical as it may ap;)ear. 



The principle, that surfaces of similar bodies increase 

 only as the squares of their homologous lines, while their 

 weights, or rather solid contents, increase as the cubes of 

 those lines, furnishes the solution. This principle is unani- 

 mously in favour of large bodies. 1 he largest circle that 

 oan.be described in a crow's breast is about 12 square inches 

 in area. If a man exposes a direct bulk of 6 square feet, 

 the ratio of their surfaces will be as 1 to 72 ; but the ratio 

 of their weight is as 1 to 110; which is l{ to 1 in favour of ^ 

 the man, provided he were within a case as well constructed 

 for evading resistance, as the body of the crow ; but even 

 supposing him to be exposed in his natural cylii . ? shape. 



this respect. 



