10 BLAIR- EXPLORATION OF THE UPPER AIR [March s, 



1873. The results obtained by these observatories showed, as was 

 pointed out by Professor Abbe and others, that the readings were 

 not sufficiently isolated from terrestrial influences, and attention was 

 again turned to kites. 



Archibald showed the value of vertical planes for steering pur- 

 poses, constructed kites of greater lifting power and in 1887 used 

 them to carry up a camera. Captain Baden Powell in England, 

 interested in the possible use of kites in war, made them large 

 enough to lift a man. Eddy, at Bayonne, N. J., in 1890, constructed 

 a diamond kite in which the ends of the cross stick were bent back, 

 thus introducing a vertical component in the planes which added to 

 their stability in flight. In 1893, Hargrave, an Australian, invented 

 the box or cellular kite. This kite, although of more complicated 

 construction than forms heretofore used, very soon displaced them 

 for every purpose and seems to contain the fundamental principle 

 upon which all stable aeroplanes are constructed. 



Eddy's work was taken up by Mr. Rotch and his assistants at 

 Blue Hill near Boston, and Hargrave's by the U. S. Weather Bureau 

 under the immediate direction of Messrs. Marvin and Potter. 

 Marvin's study of the mechanics and equilibrium of kites led him 

 to make some modifications in the original box pattern. The 

 Marvin-Hargrave kite, at present quite widely used, is not only more 

 efficient, but is stronger and, for meteorological uses, more con- 

 venient in details of construction than the Hargrave. About this 

 time Marvin designed a meteorograph and convenient hand reels for 

 the wire which were used in a series of upper air observations made 

 at seventeen dififerent stations during the summer of 1898. In this 

 series daily flights were attempted but only 44 per cent, of these 

 attempts were successful, the failures being due to lack of wind or 

 other adverse conditions. Of the 1,217 ascensions made, about 180 

 were a mile in height, while two were slightly over 8,000 feet. The 

 observations made have been reduced and are published in Bulletin 

 F of the U. S. Weather Bureau. 



Nearly all first rate weather services now have one or more upper 

 air observatories. Our own upper air work has been concentrated 

 at Mt. Weather, Va., under the immediate direction of the writer, 

 where, since the first of July, 1907, daily except Sunday, ascensions 



