\QQ ON AERIAL NAVIGATION. 



^ lower part of the wino, will always give nearly the same 

 support, and the propelling part of the surface will be at 

 liberty to act unincumbered by the leveratre of its support- 

 ing power. This plan may be modilied many different 

 ways; but my intention, as in the former case, is still the 

 principle in its simplest form.' 



A third principle upon which the leverage of a surface may 

 rhe'^|)araUelisra be prevented is by giving it a motion parallel to itself, either 



Th'rd method 

 by prcservinjj 



ofth^ 



wiiit; 



directly up and down, or obliquely so. The surface A I, hg.3, 

 may be moved perpendicularly, by the shaft which supports 

 it, down to the position K C: or, if it be supported upon 

 two shafts w'th hinges at D and E, it may be moved ob- 

 li(juely parallel to itself into the position B L. 

 Fourth me- ^ fovuth principle upon which the leverage mav be jjreatly 



thod : placing • J J , , , • • J • 1 , ' • ^. 



the hinge avoided, where only one hinge is used, is by placnig it con- 

 much below siderahly below the plane of the wing, as at the point D, 

 the wing. ^o* "^' '" respect to the surface A. It may be observed in 



The heron. the heron, which is a weak bird with an extended surface, 

 that its wings curve downward considerably from the hinge 

 to tlie tip ; hence the extreme portion, which receives the 

 chief part of the stroke, is applied obliquely to the cur- 

 rent it creates; and thus evades in a similar degree the le- 

 verage of that portion of the supporting power, which is con- 

 nected with the pvopelling power. These birds seldom carry 

 their waft much below the- level of the hinge of the wing» 

 where this principle, so far as respects the supporting power, 

 would vanish. 

 The third and By making u-se of two shafts of unequal lengtji, the 

 fourth me- ^^^q ]q^^^ mentioned principles may be blended to any required 

 bined.'^ extent, Supi)ose one hinge to be at F, and the other at G, 



fig. 3, then the surface, at the extent of its beat, would be 

 in the position of the line H M. If the surface A J, fig. 3, be 

 supported only upon one shaft, N E, be capable of being 

 forced in some degree from its rectaiig\ilar position in 

 respect to the shaft, and be concave instead of flat as here 

 represented; then the waft may be used alternately back- 

 ward and forward, according to the principles of the ma- 

 chine I have ascribed to Mr. Degen. This construction 

 combines the principles of counterpoising the supporting 

 power of one part of the surface, by that of an opposite 



part. 



