RAIN AND ITS ORIGIN IN THUNDERSTORMS. 



389 



charges become greater, they do indicate a slight tendency for the ratio of positive to 

 negative electricity to become less as the charges increase ; but it would not be safe 

 to base any deductions on the slight variations indicated. 



The effects of the storm of May 13 are again seen in the figures for highly 

 charged negative rain ; for of the 20 records of rain with higher negative charges 

 than 6 els. units per cubic centimetre of water, 18 occurred during this one 

 storm. 



Table IV is a list of the charges which equalled or exceeded 6 els. units per 

 cubic centimetre of water. 



From this it will be seen that during the storm on May 13 the negative 

 charge on the rain reached the large amount of nearly 20 els. units per cubic centi- 

 metre of water. With the exception of these the largest charges were positive 

 charges of 8 els. units per cubic centimetre of water. 



We can now turn to the question whether there is any relationship between the 

 rate of the rainfall and the charge it carries : 



TABLE V. 



In this table, columns 2, 3, and 5 give the number of two minutes' intervals 

 during which rain, having the intensities shown in the first column, was recorded as 

 bringing down no charge, a positive charge, and a negative charge respectively ; while 



