•920 Transactions of the American Institute. 



negative compared with those of the superincumbent tropical 

 current. 



Hence arise tlie many meteorological phenomena in which atmos- 

 pheric electricity plays so important a part, and in which we some- 

 times witness the most terrific consequences. 



Storms. 



The violent phenomena with wliich we are most fiimiliar are storms 

 with rain, lightning and hail. 



Every particle of cloud or fog is known to be positively electrified, 

 and to exist in the form of a small spherical balloon, in which a small 

 pellicle of water serves as an envelop to tlie interior air. This may 

 be verified by any one who M'ill let some of the particles fall upon a 

 slip of glass and submit them to microscopic inspection. 



Now this covering of water possesses all the positive electricity 

 which was distributed in the vapor which composed it. The size of 

 these vesicular globes is maintained at tlie point of balance between 

 the repulsive force of the electricity and the coliesion of the water. 



When such globules, in infinite numbers, collect to form a cloud, 

 is, as it were, a conductor, all of whose electricity is at once trans- 

 ferred to the surface ; on the contrary, the globules preserve their 

 insulation and their individual electricity, and do not part with it 

 except in a manner very slow, according as the interstitial air may 

 be more or less conductive. 



In this way some of the electricity of the interior globules does 

 slowly approach the surface of the cloud, thus enabling the globules 

 individually to contract and severally to coalesce, forming drops 

 which fall carrying their remaining electricity to the earth. 



Presently a higli degree of tension is acquired at the surface of the 

 cloud, near the negative earth, or Bear an adjacent cloud which has 

 been rendered negative by induction, and a discharge takes place in 

 the form of a flash of lightning. This makes way for still further 

 discharges from the interior globules, and facilitates a more liberal 

 formation of the rain drops. 



I have often observed the sudden increase in the torrents of rain 

 commencing in a few seconds, and continuing for a few seconds, after 

 a heavy clap of thunder. 



One clap follows another, and another, but such discharges never 

 deprive the cloud of the whole of its electricity, for as soon as the 

 excessive tension of the surface is so far reduced as to admit of the 



