ON AERIAL N AVUJ.iTION, $5 



penfln2:e must be furnished witli a vertical sal, and be ca- 

 pable, of turp.ino- fiom side to side, in addition to its other 

 inovetneiits, which effects tlie complete steerisye of the ves- 

 sel. 



AH tliese principles, upon which the su)>po't, steadiness, Experiments 

 elevation, depression, ^nd stee.a-e, of vessels for aerial '^^^^;'^'^^""^'»;'^ 

 nuvis^ation, dej)eiid, have been abundantly veritied by expe- 

 riments both upon a sp.iall and a lart^e sode. Last year I 

 made a niitchine, liaving a surface of 300 square feet, which 

 was accidentally broken before there was an opportunity of 

 trying the effect of the propelling apparatus; but its steer- 

 age and steadiness were perfectly proved, and it would sail 

 ohlifjUely downward in any direction, according to the set 

 of the rudder. Evert in this state, when any person ran 

 forwa:-d in it, with his full speed, taking advantage of a 

 gentle breeze in fiont, it would bear upwaid so strongly as 

 scarcely to allow him to touch the ground; and would 

 frequently lift him up, and convey him seveial yards toge- 

 ther. 



Tlie best mode of producing the propelling power is the The best mode 



only thi.io', that remains yet untried toward the completion ^^ I'loducing 



. . . . thf! jiropelling 



of the invention. I am preparing to resume my experiments power only re- 

 upon this sultject, and state the following observations, in, "'^ins. 

 the hope that others may be induced to give their atteatiou 

 towards expediting the attainment of this art. 



The act of flying is continually exhibited to our view; Flight of birds, 

 and the principles upon which it is eti'ected are the same as 

 those before stated. If an attentive observer examines the 

 waft of a wing, lie will perceive, that about one third part, 

 toward the extreme point, is tu%"ued obliquely backward; 

 this being the only poriion, that has velocity enough to 

 overtake the curreat, passing so rapidly beneath it, when ia 

 this unfavourable position. Hejice this is the only portion 

 that gives any propelling force. 



To make this more intelligible, let A B, Fig. 4, be a 

 section of this part of the wing. Let C D represent the 

 velocity of the bird's path, or the current, and BD that 

 of the wing in its waft : then C E will represent the magni- 

 tude and direction of the compounder actual current strik- 

 ing the under surface of the wing. Suppose E F^ perpen- 

 dicular 



