A FLASH OF JJiJflTNING 



77 



Fig. 2. The Outflow into the Cloud which has less than its Normal Chaege. 



occurs. This evidence is presented in tlie figures, which are reproduced 

 from photographic plates. 



Fig. 1 represents in cross-section the cloud which is overcharged 

 with the negative fluid. The cross-section is at right angles to the 

 end of the long flash which connects the two clouds. The discharge 

 lines on this plate resemble a system of rivers and tributaries, which 

 penetrate the cloud. These drainage lines elongate up stream. Some 

 of them are sharply defined. Others, for reasons which will be ex- 

 plained, are seen only in shadowy outline. 



Before the flash occurred, the falling drops, which were all highly 

 charged, repelled each other. After the discharge those drops which 

 happened to lie in the path of some one of these tributary discharge 

 lincb, have lost their overcharge. There is then an attraction between 

 such drops and those which were slightly outside of these drainage lines, 

 and which are therefore still overcharged. These two groups of drops 

 are intimately commingled, as is shown by the intricate nature of the 

 system of drainage channels. As they continue their fall to earth, they 

 coalesce, and a brief dash of unusually large drops of rain is observed. 



The discharge pours through the long hole in the air, in which the 

 conditions are like those which exist in a vacuum tube. The conditions 

 which exist in the cloud at the other end of the flash are shown in 

 Fig. 2. 



