378 Guy-Lussac's and Biot's Aerostatic Voyage. 



trometcr: it was found to be resinous. We performed khia 

 experiment twice at the same moment : first, by destroying 

 the atmospheric electricity by the influence of the vitreous 

 electricity of the electrophorus ; and secondly, by destroy- 

 ing the vitreous electricity extricated from the electrophorus 

 by means of the atmospheric electricity. In this manner 

 we were able to ascertain that the latter is resinous. 



This experiment indicates that electricity increases with 

 the height; a result agreeable to what had been concluded 

 from theory, according to the experiments of Volta and 

 Saussure. But since we are now acquainted with the good- 

 ness of our apparatus, we hope to be able to verify this 

 fact by a greater number of trials during another journey, 

 Our observations of the thermometer indicated on the 

 other hand a temperature decreasing from the earth up- 

 wards, which is agreeable to the results already known. But 

 the difference was much less than we should have expected. 

 For, on rising to the height of 2000 toises, that is to say, 

 far above the lower limit of permanent snow, in that la- 

 titude we did not experience a temperature lower than ]0*o° 

 of* the centigrade thermometer (8'4° of Reaumur) ; and at 

 the same moment the temperature of the observatory of Pa- 

 ris was 17*5° of the centigrade scale, or 14° of Reaumur. 



Another very remarkable fact given by our observations 

 is, that the hygrometer always advanced towards dryness 

 as we rose in the atmosphere; and that in descending it 

 gradually returned to humidity. When we set out it indi- 

 cated 60&° at \&b 9 of the centigrade thermometer; and at 

 the elevation of 4000 metres, though the temperature was 

 only 10-5°, it indicated no more than 30°. The air then 

 was much drier in the high regions than it is near the sur- 

 face of the earth. 



To^rise to this height we had thrown out almost the 

 whole of our ballast : we had scarcely four or five pounds 

 left. We had therefore attained to that height to which 

 it was possible for the balloon to rise with two persons at 

 once. As we were, however, exceedingly anxious to ter- 

 minate; the observation of the compass, M. Cuiy-Lussac 

 proposed to me to ascend alone to the height of 6000 

 metres (3000 toises), in order to verify our "first results. 

 We were to deposit our instruments when we reached 

 the earth, and to carry up in the car only the barometer 

 and compass. When we had formed this resolution we 

 suffered the balloon to descend, losing as little gas as pos- 

 sible. We observed the barometer when we entered the 

 clouds, and it gave us 1223 metres, or GOO toises of eleva- 

 tion. 



