OK AERIAL LOCOMOTION. 



Bv F. H. Wenham. 



The resistance against a surface of a defined area, passing rapidly 

 through yiehling media, may be divided into two opposing forces; 

 one arising from the cohesion of the separated particles and the other 

 from their weight and inertia, which, according to well-known laws, 

 will require a constant power to set them in motion. 



In plastic substances the first condition, that of cohesion, will give 

 rise to the greatest resistance. In water this has very little retarding 

 effect, but in air, from its extreme fluidity, the cohesive force becomes 

 inappreciable, and all resistances are caused by its weight alone ; there- 

 fore, a weight suspended from a plane surface, descending perpendicu- 

 larly in air, is limited in its rate of fall by the weight of air that can be 

 set in motion in a giv'cn time. 



If a weight of 150 pounds is sus[)ended from a surface of the same 

 number of square feet, the uniform descent will be 1,300 feet per minute, 

 and the force given out and expended on the air, at this rate of fall, 

 will be nearly six horse-power; and, conversely, this same speed and 

 power must be communicated to the surface to keep the weight sus- 

 tained at a fixed altitude. As the surface is increased so does the rate 

 of descent and its accompanying power, expended in a given time, 

 decrease. It might therefore be inferred that, with a sufficient extent 

 of surface reproduced, or worked u)) to a higher altitude, a man might 

 by his exertions raise himself for a time, while the surface descends at 

 a less speed. 



A man in raising his own body, can i)erform 4,250 units of work, 

 (that is, this number of pounds raised 1 foot high per minute,) and cau 

 raise his own weight (say 150 pounds) 22 feet per minute. But at this 

 speed the atmospheric resistance is so small that 120,000 square feet 



* A paper read before the Aeronautical Society of Great Britaiu, June 27, 18(50, 

 '•On At"rial Locoiiiotiou, and tlio Laws by wbicli Heavy Bodiea Impelled fcbrongll 

 tbe Air, are Sustained." (From tbe Tranxaciions of the Aeronautical Society. First 

 Annual Report for tbe year ISOti, pp. 10-40.) Notwitbstauding its date, tbis paper 

 contains so good a presentation of tbe problinn of ai'ronaut ics, that it deserves a 

 wider circulation tban it bas received. 



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