jj On the Modifications of Clouds, arid. 



of vapour ; but at other times is interposed between the 

 latter and a supervening current from another chmate, in 

 which case it may be affected by both currents. 



The cumulus has been just now considered as an insu- 

 lated body, consisting of perfectly moveable parts which 

 accommodate themselves to the state of re/rt/H///g' electricity. 

 We shall attempt to explain the nature of the cirrus by 

 comparing it to those imperfect conductors, which being 

 interposed between electrics and conductors, or between thu 

 latter in diflerent states, serve to restore by degrees the equi- 

 librium of the electric fluid. 



If a lock of hair be properly fixed on the prime conductor 

 and electrified plus, the hairs will be separately extended at 

 as great a distance from each other as possible ; in which 

 §tate they will continue some time. The reason appears to 

 be, that the contiguous air is then minus ; and consequently 

 these two moveable substances put themselves into the state 

 most favourable to a communication which is but slowly 

 effected between bad conductors. 



The same appearances will take place if the lock be elec- 

 trified minus, the contiguous air being plus ; and in each 

 case the hairs will move from a body similarly electrified 

 and brought near then), and touards one contrariwise elec- 

 trified, 8cc. Moreover, if we could insulate such a charged 

 lock in the midst of a perfectly tranquil atmosphere of 

 sufficient extent, in which particles of conducting matter 

 were suspended, the latter would be attracted by it so long- 

 as the charge continued 3 after which they would be at large 

 as before. 



Dry air being an electric, and moist air but an indifferent 

 conductor, it is reasonable to suppose that an immediate 

 communication of electricity between masses of air differ- 

 ently charged can scarcely happen to any great extent, ex- 

 cept by tlie intimate mixture of such masses ; an occurrence 

 which may possibly result in some such cases, and occasion 

 strong winds and commotions in the atmosphere. If we 

 consider how frequentlv, and to what an extent, the elec- 

 tricity of the air is disturbed (as appears from numerous 

 experiments) by evaporation, by the formation and pas- 

 sage ot clouds, by elevation or depression of temperature, 

 (by friction upon surfaces of ice ?) it seems probalile that 

 the particles of water floating in a calm space may be fre- 

 quently converted into conductors, by wliich the equilibrium 

 is in part restored after such disturbance. 



Viewing the cirrus in this light, it becomes important for 

 those wlio are well versed iu electricity to study its appear- 

 ances. 



