THE PROBLEM OF FLYING. 



191 



is performed by birds iucessautly and it is in virtue of a perfect 

 adaptation of tlie form of tlieir wiugs to any aerial motion tliat their 

 flight appears to ns so sure, graceful, and beautiful. 



In the same way a man can move through the air and have the gen- 

 eral ability to guide his apparatus by a constant sliiftiiig of the center 

 of gravity. Descent should not be at first tried from great elevations, 

 for such a feat requires practice. In the beginniug, the height should 

 be moderate and the wings not too large, or the wind will soon show 

 that it is not to be trifled with. In fact, under some circumstances, one 

 may be swept off toward still higher regions, the descent from which 

 might well be disastrous. It therefore seems best that the wings 

 should not exceed from 8 to 10 sguare meters (somewhat over 80 to 100 

 square feet), or that the experiment should be conducted in any wind 

 blowing more than 5 meters x)er second (nearly 1,000 feet a minute), 

 which represents a gentle breeze. A good run against the wind, how- 

 ever, and a leap from a safe height of 2 or o meters may secure a flight 

 of 15 or 20 meters. 



FlQ. 2. 



Continual practice will enable the exj^erimenter to withstand a 

 stronger breeze, to increase the surface of the wings to 15 square meters 

 (100 square feet), and to start from a greater elevation, especially if 

 there be a moderate slope beneath him with a soft, yielding surface. 

 After becoming sufficiently expert to deviate from a straight line, the 

 experimenter may enjoy the sensation of flying, but it is always a nec- 

 essary condition that he should face the wind while descending, as the 

 birds do. If then flight is attempted with the wind, it must be more 

 rapid than the wind, or the result will be very apt to be a dangerous 

 somersault at the time of coming to the ground, so that it is, on the 

 whole, most advisable to follow the lessons of the birds, who ascend 

 and descend against the wind. 



