348 



AERONAUTIC VOYAGES. 



reflected by the cloivd, examiued with the polariscope, presented no trace of 

 polarization. 



The greatest height at which M. Welsh arrived was attained in his fourth 

 voyage, performed the 10th of November. The ascent took place at 2 hours 

 21 minutes, and the descent, near Folkstone, 23 leagues E.SE. of London, at 

 3 hours 45 minutes. The height reached was 6,989 meters ; minimum tem- 

 perature observed — 23^.6; minimum pressure 310.9 millimeters. On the earth 

 the barometer indicated 761.1 millimeters, and the thermometer +9°. 6. A 

 first cloud Avas encountered at 254 meters, Avhose upper surface reached a height 

 of 600 meters. There occurred next a space of 620 meters, free from all sensible 

 vapor ; but, at a height of 1,220 meters, a new cloud was met with, which ter- 

 minated at 4,494 meters. Beyond this there were only a few cirri at a very 

 great height. 



"We see that the English aeronauts only once approached, though without 

 attaining, the height of 7,000 meters, reached by Gay Lussac, and by Barral 

 and Bixio. The very low temperature of — 23°. 6, observed by Welsh in his 

 last ascension, would certainly have appeared extraordinary if our countrymen, 

 in their expedition of July 27, 1850, had not encountered a cloud having a 

 much lower temperature. The air collected by Mr. Welsh was analyzed by 

 M. Miller, who found its composition the same with that of normal air. The 

 hygrometrical observations which Mr. Welsh made with care, and in great num- 

 ber, by help of the psychrometer and hygrometer of M. Ecgnault, did not indi- 

 cate any considerable dryness. On the contrary, even in the highest regions, 

 the relative atmospheric humidity approached saturation. 



VII. 



-THE GREATEST HEIGHTS REACHED, AND THE TEMPERATURES OBSERVED, 

 IN THE UPPER REGIONS OF THE ATMOSPHERE. 



It is worthy of remark that, to the present time, man has not ascended into the 

 eitmosphere as high as the aerial stratum which surrounds the loftiest mountain 

 summits of tlie Old and New World. Kintschindinga and Aconcagua, the former 

 8,592, the latter 7,291 meters high. In the ascent of mountains, barely 6,000 

 meters may be assigned as the height to which human effort has attained. In 

 June, 1802, my illustrious friend, Alexander Humboldt, accomj)anied by M. 

 Bonpland, ascended Chimborazo to the altitude of 5,878 meters. In December, 

 1831, another of my friends, M. Boussiugault, accompanied b5^ Colonel Hall, 

 climbed the same mountain to the height of 6,004 meters above the level of the 

 sea. If we add to these two celebrated excursions the aeronautic voyages of 

 Lhoest and Robertson, July 18, 1803; of Gay Lussac, September 16, 1804; 

 of MM. Barral and Bixio, July 27, 1850; of M. Welsh, August 26 and No- 

 vember 10, 1852, we' have the sum of all the enterprises in which man has 

 succeeded in maintaining his position for a few instants in the strata of air 

 situated from 6,000 to 7,000 meters above the mean level of the seas. The 

 following table recapitulates the thermometric and barometric observations 

 made under these rare circumstances : 



Names. 



Humboldt and Bonpland 



Lhoest and Robertsou 



Gay Lussac 



Boussingault and Colonel Hall 



Banal and Bixio 



Welsh 



Welsh 



Dates. 



June 24, 1802 

 July 18,1803 

 Sept. J(j, 1804 

 Dec. 16, 1831 

 July 27,1800. 

 Aug. 26, 18.72 

 Nov. 10,1852 



Greatest 

 heights 

 attained. 



Lowest barometric 



pressures oliserved. 



(Reduced to 0^) 



Meters. 

 5, 878 

 6,831 

 7,016 

 6, 004 

 7,049 

 C,096 

 6, 989 



Millimeters. 

 376.7 

 336. 

 323.8 

 371.1 

 315. 

 371.1 

 310.9 



Lowest 



temperatures 



observed. 



Degrees. 



— 1.6 



— 6.9 



— 9.5 



-1-7.8 

 —39.7 

 —10.3 

 —23.6 



