CHAPTEK IV.— SCIENTIFIC USES OF BALLOONS AND 



KITES. 



Scientific Balloon Ascensions. 



The first scientific balloon voyage was made (in London) bv Dr. 

 John Jeffries, of Boston, Massachusetts, in the year 1784.* The 

 barometer fell to 21.25 inches (altitude about 9300 feet). 



Some of the ascensions and the heights reached are noted below : 



FEET. 



Gay-Lussac and Biot, 1804 .... 23,000 



Barral and Bixio, 1850 . . . about 23,000 



Welsh, 1852 " 23,000 



Glaisher, 1862 29,000 



Croce-Spinelli, j^g^^ _ ^ ^^^^^ 29,000 



Sivel and Tissandier. ) 



Berson, 1894 30,000 



There are three ways in which balloons may be used for scientific 

 ol)servations — (a) as captive balloons at comparatively small heights ; 

 (h) in ascensions carrying observers ; and (c) as free balloons bearing 

 self -registering instruments, but no observer. 



Captive balloons are convenient ; but they cannot be sent to gi"eat 

 heights, and, in general, it is difficult to keep them at a constant alti- 

 tude while strong winds are blowing. 



Balloons carrying an observer are enabled to obtain the most trust- 

 worthy results, but the heights which they command are limited to 

 some 20,000 feet. 



Free balloons, carrying only self-registering instruments, have lately 

 been brought to great perfection, and an extreme height of eleven 

 miles has been reached (18,450 m). 



MM. Gustave Hermite and Besangon succeeded, in 1893, in sending 

 a small balloon to the prodigious height of 52,500 feet (nearly ten miles). 

 The weight of the whole apparatus was about 17 kilos (37.5 pounds), 

 and a complete set of self- registering instruments was carried. 



* The ascension of the brotliers Montgolfier was made in 1781J. 



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