346 How Clouds hcwne eleStrifed. [Book, IV. 



their virtue to other bodies which are fufceptible of it, 

 being infulated, and at a convenient diftance. As air, 

 therefore, is an idio-electric body, it is not unphilofo- 

 phical to fuppofe, that in ilormy weather efpecialiy, 

 when it is common to obferve the clouds and the wind 

 take contrary courfes, a part of the atmofphere 3 rufh- 

 ing by the other, may caufe the air to be electrified by 

 the friction of its own particles, or by rubbing againtl 

 terreflriai objects -which it meets in its parTage, or 

 perhaps againll the clouds themfelves. It is pro- 

 bable alfo, that the inflammable fubftances, which 

 arife and accumulate in the cloudy regions, contribute 

 to increafe the effects, not only of themfelves, but, 

 perhaps, ftill more, by the electric matter which they 

 carry along with them. Another circumftance, which 

 further inclines me to make this inference is, that 

 thunder florms are more frequent and tremendous 

 in thofe times and places, when and where we have 

 realbn to conclude that thefe exhalations are in the 

 greateft abundance in the atmofphere, as in warm fea- 

 fons and climates, as well as in thofe places where 

 the earth is filled wirji fubftances capable of furnifhing 

 a large quantity of thefe exhalations, and in particular 

 in the neighbourhood of volcanoes. 



A cloud in a thunder florin may be confidered as a 

 great conductor, actually infulated and electrified ; and 

 it may be fuppofed to have the fame effect upon thofe 

 non- electrics which it meets with in its courfe, as our 

 common conductors have upon thofe which are pre-- 

 fented to them. If a cloud of this kind meets with 

 another which is not electrified, or lefs ib than itfelf, 

 the electric matter flies off from all parts towards this 

 cloud ;' hence proceed flafhes of lightning, and the for- 

 midable report of thunder. 



f Thunder 



