:>72 Account of an Aerostatic Voyage 



nus. We tried its magnetic force several times before wer 

 quitted the earth. It made twenty oscillations in 141 se-t 

 conds of the sexagesimal division; and, as we obtained the 

 same result a great number of times without the deviation 

 of half a second, it may be considered as very exact. We 

 used for our observations two excellent watches that beat se- 

 conds, lent to us by an ingenious watchmaker, M. Lcpine. 



Besides this apparatus we carried with us a common va- 

 riation compass and a dipping needle ; the former to ob- 

 serve the direction of the magnetic meridian, and the other 

 to determine the variation in the inclination. These in- 

 struments, much less sensible than the preceding, were 

 destined only to point out to us the differences in case any 

 verv considerable should take place. That we might obtain 

 onlv comparative results, we placed all these instruments in 

 our car when we observed on the earth the oscillations of 

 the first needle. No iron was employed in the construction 

 of the car or of the machine. The only articles of iron we 

 carried with us, a knife, a pair of scissars, and two penr- 

 knives, were suspended in a basket below the car at the di- 

 stance, of from 25 to 30 feet ; so that they could have no. 

 sensible influence on the magnetic virtue. 



Besides the principal object of this voyage, we proposed 

 also to observe the electricity of the air, or rather the diffe- 

 rence in the electricity of the different strata of the atmo- 

 sphere. For this purpose we carried with us metallic wires 

 of different lengths, from 60 to 300 feet. By suspending 

 these wires close to the side of our car from the extremity 

 .of a glass rod, we were brought into communication with 

 the lower strata of the atmosphere, and enabled to call forth 

 their electricity. To determine the nature of this electricity 

 we had a small electrophorus weakly charged, the resin of 

 which had been rubbed with earth before we ascended. 



We proposed also to bring back air collected at a great 

 height. To accomplish this part of our plan, we had an 

 exhausted glass balloon closely shut, so that to fill it with 

 air nothing was necessary but to open it. We were pro- 

 vided also, as may be readily conceived, with barometers, 

 thermometers, electrometers, and hygrometers. We had 

 likewise metallic disks to repeat the experiments of Volta 

 in regard to electricity excited by simple contact ; and we 

 carried with us different animals, such as frogs, birds, and 

 insects. 



We ascended from the garden of the Conservatoire des 

 Arts on the 24th of August, at ten in the morning, in the 

 presence of a few friends.. The barometer stood at 28 in. 



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