KITE-FLYING IN 1897. 



63 



changing their tint with every motion, the casual observer has an 

 impression that he is gazing at a flock of real birds, with a notion 

 of w^liite, gray, pink, blue, and purple gulls, uncommonly wide of 

 wing and unusually fascinating. 



Now and then one or another sails away from its place and 

 poises itself for a few moments, then returns nearly to its former 

 position; while another takes a sudden dive downward, ending in 

 a graceful parabola which brings it to a new point on its original 

 level. Sometimes one kite will move almost directly at another, 

 which shyly sidles away ; when the first ceases its movement, droops, 

 and sinks down, until, just in the nick of time, a strong young zephyr 

 catches it and buoys up its faltering pinions. 



The cause of all these apparently purposed movements being 

 invisible to the beholder, some degree of reflection is required to rid 

 one's self of a lurking idea that these are animate things. 



Elements of the Hargrave Kites. 

 From the Tables of Blue Hill Meteorological Ohservatory. 



The lifting surface of these several kites is assumed to be the total 

 surface of the side planes (upper and lower). The sticks have a 

 rectangular or elliptical cross-section. 



The kites are very stable, and fly in recorded wind velocities of 

 from six to twenty metres per second. The angular attitudes reached 

 by the first two kites average between forty-five and fifty-five degrees, 

 and those reached by the last two average between fifty and sixty de- 

 grees. The pull in a recorded wand of ten metres per second aver- 

 ages about five kilogrammes per square metre of lifting surface. 



The Blue Hill method of testing kites is to fly them with a short 

 line, usually from fifty to one hundred metres long, and to make fre- 

 quent and regular observations of the angular attitude and of the 

 pull. The instruments employed are a surveyor's transit and a spring 

 balance. Tests are usually made under widely varying conditions of 

 wind velocity, and the kites flying at the highest angles and those 

 exerting the greatest pull are easily selected. The work in view 

 consists of raising a meteorograph of known weight under varying 

 conditions. 



