2 THE LATE ME. WILLIAM STURGEON ON 



their aqueous character is precisely the same ; and it is only 

 the elevated aerial locality and the rapidity with which the 

 latter is formed, that gives it a superior electric tension, and 

 enables it to discharge its electric element with violence in 

 the shape of lightning. 



55. With respect to aerial locality or altitude, I believe it 

 is now pretty well understood that the higher regions are 

 more densely charged with the electric element than those 

 below. The experiments of MM. Gay Lussac and Biot, 

 during their memorable balloon excursion in the year 1804, 

 showed that the air, at a lower altitude, was negative to that 

 in which the balloon was floating. The experiments which 

 I have myself made with electric kites, at different altitudes 

 at the same time, have invariably developed similar results: 

 for in every case, during serene weather, the highest kite was 

 positive to those beneath it, and the lowest negative to all 

 those above it ; but still positive with respect to the ground 

 on which I was standing. Hence, during serene weather, 

 there appears to be a regular increase of electric charge in 

 the atmosphere, from the ground upwards, as some function 

 of the altitude ; and as aqueous vapour suspended in the air 

 necessarily partakes of the same electric character, it is easy 

 to understand that a rapid condensation of that situated at a 

 high altitude would form cloud of a far superior electric in- 

 tensity to any that could be formed nearer to the ground. 

 Moreover, since in all cases the formation of cloud pre- 

 cedes discharges of lightning, and thunder-storms are fre- 

 quently attended with the most violent hail showers, even 

 during the hottest weather, there can need no further indi- 

 cation of a thunder-cloud's formation being the effect of a 

 sudden depression of temperature ; and, consequently, all 

 thunder-clouds, whatever change they may suffer afterwards, 

 are originally electro-positive. No experiment, that I am 

 acquainted with, can illustrate this fact more correctly than 

 that first shown by Franklin himself, with his chain and can. 



