1C2 . Meteorological Olservations on a Thunder Slorm. 



During the time of these nbservaiions, the higher cloud, 

 which siippHcd so n)uch clccliicits-, was not diminished in 

 the least. On the contrary, it continued to enlarce in its 

 dimensions, and chiefly towards the wind, as may be seen 

 bv its overhanging in the sketch. 



Now the quantity of electricity supplied by this clovid 

 continually during an hour, was probably 30 times as much 

 as it could possibly contain. The question then is : Where 

 did it come from ? The increasing of the cloud furnishes 

 an answer to this question; tor it could not increase without 

 the addition of vapour, and that addition could come only 

 from the atmosphere. This was proved by the manner and 

 place of increase, which was at the top, and at the most 

 prominent parts facing the wind. That vapour, being trans- 

 parent, had ihe highest charge of electricity. The upper 

 cloud (though positive to the under) was minus to that va- 

 pour, and silently attracting from it the superabundant elec- 

 tricity, which it gave otT visibly to the under cloud, which 

 was still less chargcif, and which was kept so by the earth 

 (wiiich may be considered as quite negative) immediately 

 drawing away that charge in sparks. 



Now it is evident by this progress of the electric fluid to 

 the earth, that the electrified vapour must have been con- 

 densed to the smaller compass of the cloud, and have been 

 deposited on its surface, occasioning that very great increase 

 of cloud. This seems to show that a storm of lightning 

 will always occasion a current of wind from the external re- 

 gions towards itself; and hence a dead calm preceding a 

 storm, and the fall of the barometer, as this is the focus of 

 condensation. 



I have since repeatedly, in stormy weather, seen clouds, 

 under this efl'ect of increase, sometimes increasing at one 

 'end, and diminishing at the other by slow rain, when near 

 a mountain ; but 1 have seldom seen the theoretic form (if 

 1 may be allowed the expression) so evident (except among 

 mountains, where it is unlimited, hut the lightning rarely 

 seen,) as in the case I have stated: nor can this conforma- 

 tion ever be seen but when the barometer is low or falling. 

 The lower cloud was three or four times as long, in pro- 

 portion, as it is represented in the drawing, in which it is 

 necessarily shortened for the convenience of exhibiting both 

 of its ends. 



Before concluding, I beg leave to add a few thoughts on 

 the medical action of cleciriclty. 



First, 1 think that electricity entering; the body by a good 

 conductor in contact, and going out by another in contact, 



produces 



