94 Ascending Lightning? 



thunder, the clouds are at an elevation at most of 368.5 yards 

 of perpendicular height ; when the interval between the two 

 phenomena is i a second, the height of the clouds cannot be mor^^ 

 than 184 yards ; and when there is an interval of y*^, ^-^^ /^j, 

 and ^^ of a second, then the heights of the lowest clouds will 

 respectively correspond to about 148, 111, 74, and 37 yards. 



The weather-cock on the dome of the Invalides has a ver- 

 tical elevation of 112 yards. Suppose, that, during the time 

 of a storm, an observer placed near the monument were to 

 perceive one of these flashes, which do not appear to quit the 

 clouds^ and he was also sure that the thufider succeeded the 

 lightning, after a short interval of -^-q of a second. It would 

 result, as we have just seen, that the clouds, the supposed focus 

 of the lightning, could not be more than 111 yards in height, 

 and that they must have enveloped the weather-cock of the 

 dome. But if the weather-cock has remained free, and if the 

 clouds have been always higher, it will then he proved that the 

 detonation has not been produced in the midst of them, and the 

 theory of ascending lightning might then produce in its favour 

 an argument which would be almost irresistible. 



At Strasburg, where the steeple reaches an elevation of 155 

 yards, the same mode of observation might be extended to the 

 case in which there was an interval between the light and the 

 sound, amounting to 1% of a second. In the vicinity of moun- 

 tains, if we had previously determined a certain number of well 

 defined points, it would be easy to advance to entire seconds. 

 Finally, entire seconds of interval, would be no where an ob- 

 stacle to the application of the method, if recourse were had to 

 balloons, with whose help the exact height of clouds might be 

 determined ; or at all events, their inferior limit. 



I know not if I be at all deceiving myself, but sure I am 

 that observations of this sort peculiarly merit the attention of 

 philosophers. How interesting would it be to put an end, 

 by a simple comparison of figures, to the interminable question 

 of ascending lightning, that is to say, of lightning which it 

 is supposed must ascend from the earth. As for those who 

 suppose that there are two currents, one ascending, and the 

 other descending, which invariably co-operate in the production 

 of these phenomena, they probably may find in the same set of 



