38 



obtained its charge part of it came down suddenly in the 

 form of rain. As the rain came lower its electric tension 

 would increase until it got near enough the ground to 

 relieve itself with a flash of lightning, almost immediately 

 after which the i&rst rain would reach the ground. 

 It has often been noticed that something like this often 

 takes place; it often begins to pour immediately after a 

 flash of lightning, so much so that it seems that the elec- 

 tricity had been holding the rain up and it was only after 

 the discharge that it could fall. This, however, cannot be 

 the case, for the rain often follows so quickly after the flash 

 that there would not have been time for it to fall from the 

 cloud unless it had started before the discharge took place. 

 If on the other hand C receded from E, it would again 

 be in a position to accept more electricity, or would again 

 become negative. In this way, a cloud in forming, or when 

 first formed, would appear negatively charged ; soon after it 

 would become neutral, and then if it moved to or from the 

 earth it would appear positively or negatively charged. 



If the air was very dry, as it is in the summer, any 

 exchange of electricity between the earth and the cloud 

 would cause forked lightning, in the winter it would 

 take place quietly, by the conduction of the moist atmo- 

 sphere. 



In this way then there would sometimes be positive, 

 sometimes negative lightning; sometimes the discharge 

 would be a forked flash or spark, sometimes a brush or sheet 

 lightning. And if clouds are formed in several layers, as 

 would be represented by another conductor D outside C, 

 then in addition to the phenomena already mentioned, 

 similar phenomena would take place between C and D ; and 

 if in addition to this we were to assume that there are 



