»24 A<counl of an Atrostaiic Voyag::. 



vary, the magnetic force ought not to have varied either; 

 unless we choose to suppose that the magnetic force could 

 varv exactly in a contrary direction, and in the same ratio, 

 as the cosine of its inclination; which is in no manner pro- 

 bable. We should have besides, in support of our conclu- 

 sion, the experiment of the inclination made at the height 

 of 3863 metres, or 198^2 toises, which proves that at this 

 height the inclination did not vary in a sensible, manner. 



\Vhen we reached the height of 431 1 metres, I presented 

 to a small magnetic needle, and in the direction of the mag- 

 netic force, the lower extremity of a key. The needle was 

 attracted, and then repelled by the other extremity of the 

 key, which I made to descend in a direction parallel to it- 

 self. The same experiment, repeated at 6107 metres, was 

 attended with the same success ; a new and very evident 

 proof of the action of terrestrial magnetism. 



At the height of 656) metres, or 3353 toises, I opened 

 one of my two glass balloons, and at that of 6636 metres, 

 or 3405 toises, I opened the second: the air entered into 

 both with a hissing noise. At length, at 11 minutes after 

 three o'clock, the balloon being completely full, and having 

 no more than 15 kilogrammes of ballast, [ resolv(;d to de- 

 scend. The thermometer was then at 9-3" below the tem- 

 perature of melting ice, and the barometer at 32*88 centi- 

 metres J which gives for mv greatest elevation above Paris 

 6977*37 metres, or 3379*9 toises; or 7016 metres, that is, 

 3600 toises above the level of the sea. 



Thouoh well clothed, I began to feel cold, especially in 

 the hands, which I was obliged to keep exposed to the air. 

 jMy respiration was sensibly confined, but I wa? still far 

 from experiencing any uneasiness so disagreeable as to 

 oblisr:e me to descend. My pulse and respiration were very 

 much accelerated ; breathing, therefore, very frequently in 

 very dry air, it need excife no surprise that my throat 

 should be so dry as to make it painful for me to swallow 

 bread. Before I set out I had a slight head-ache, arising 

 from the fatigue of the preceding clay, and being up all 

 nisht, and it continued the whole day without its appearing 

 to increase. These are all the inconveniences I experienced. 



A pliDsnomcnon which struck me at this height was to 

 see clouds above me, and at a distance which appeared to 

 be considerable. In our first ascent the clouds were not 

 sustained at a greater height than 1 1 69 metres, or 600 toises ; 

 and abosT, the heavens were exceedinglv pure. The colour of 

 them in the zenilh was even so intense that it might be com- 

 pared to Prussian blue; but in the last voyage I could not 

 sec clouds below me. The sky was much filled with va- 

 pours. 



