and extraordinary Electrical Phcenomena, 335 



those most intensely charged will cause the electricity of the 

 sides, or portions of other clouds nearest to them, to be elec- 

 trified in a different state, according to the well-known laws 

 of electrical induction: and as the larger clouds increase in 

 density or electrical intensity, they will discharge portions of 

 their electricity to the smaller and less intensely charged 

 clouds ; these again may discharge themselves to more remote 

 clouds that are still more slightly charged, and thus a succes- 

 sion of flashes of lightning and peals of thunder may occur 

 for some time. But if the general state of the atmosphere 

 below the clouds be very damp, the superabundant electricity 

 would be quietly conveyed to the earth without producing any 

 electrical appearances whatever. 



In those regions of the atmosphere where clouds float or 

 are formed at a considerable elevation, and where the air is 

 much more rare than near the surface of the earth, the resist- 

 ance to the passage of electricity through it is much less than 

 near the ground, and consequently the discharges from cloud 

 to cloud will be more frequent and to greater distances than 

 from the clouds to the earth. 



If the clouds are rapidly formed and discharge their elec- 

 tricity frequently to the earth, it is probable that a very large 

 amount of rain will ensue; for during the time they are charged, 

 the small particles of water of which they are composed will 

 be repelled from each other by the diverging power of their 

 electricity ; whilst the moment a discharge takes place, espe- 

 cially if it be to the earth, the electricity which kept the par- 

 ticles from uniting together being removed, the drops of water 

 will immediately unite in immense quantities, and, falling to 

 the earth, will suddenly increase the shower, not only in quan- 

 tity but in the size of the drops, as is frequently noticed by 

 attentive observers. As the different strata of air continue to 

 mix, the clouds increase and again become charged with elec- 

 tricity, the drops again diverge by repulsion, and the rain 

 ceases to fall as copiously as it did soon after the discharge of 

 electricity to the earth ; in this manner we may account for 

 the occasional change during a thunder-storm, from an im- 

 mense profusion to a moderate fall of rain, and vice versa. 



In a thunder-storm prevailing over a considerable extent of 

 country, and with the clouds at a great elevation, the discharges 

 of electricity may pass several miles through the air from one 

 cloud to another ; in such cases an observer may have con- 

 siderable difficulty to ascertain in what portion of the sky the 

 lightning has prevailed ; but our late eminent president, Dr. 

 Dalton, has elegantly described, at page 203 of the second 

 edition of his Meteorology, how the difficulty can be explained. 



