1883.] Electric Discharge with Chloride of Silver Battery. 157 



920,000,000 volts would be required, but this potential would be 

 lessened by the diminution of the atmospheric pressure at the height 

 of a kilometre, namely 607*4 millims. (799,210 M), or a mean pressure 

 of 713-8 millims. (939,211 M) between 1 kilometre and the earth. 

 Taking the mean pressure 939,211 M, it would require 864,000,000 

 volts to produce a discharge between a cloud (regarded as a point) 

 1 kilometre high and the earth. 



It is extremely difficult to conjecture how a cloud can become 

 charged to such an enormous potential, unless the charged molecules 

 balance each other (as those of a stratum in a vacuum tube may be 

 conceived to do) until a disturbing cause breaks up the arrangement ; 

 and then the whole of them are discharged in one direction with 

 their aggregate potential. 



We may add that less than ] 5,000 cells would not have sufficed to 

 make out the fact that the intensity of force to produce a discharge 

 between a point and disk or two points becomes a constant after 9,000 

 to 11,000 cells has been reached. 



The following table gives the ratios of the striking distances be- 

 tween a point and a disk and two points respectively, taking those 

 between two disks as unity. And also the relation between the 

 striking distances between a point and a disk and between two points, 

 taking those between a point and a disk as unity. 



Cells. 



Ratio between point 



and disk to that 

 between two disks. 



Ratio between two 



points and that 

 between two disks. 



Ratio between two 



points and 

 that between a point 

 and disk. 



With 1,000 



0-60 



0-84 



1-40 



2,C00 



1-32 



115 



0-87 



3,000 



2-09 



1-94 



0-93 



4,000 



2-68 



3 37 



1-26 



5,000 



3 -42 



4-34 



1-27 



6,000 



3 -82 



4-65 



1-22 



„ 7,000 



3 91 



4-72 



1-21 



8,000 



3-94 



4-71 



1-20 



„ 9,000 



3-89 



4-65 



1-20 



„ 10,000 



3-80 



4-51 



119 



„ 11,000 



3-69 



4 35 



118 



„ 12,000 



3-58 



4-18 



1-17 



„ 13,000 



3-46 



4-00 



1-16 



„ 14,000 



3-39 



3-84 



1-13 



„ 15,000 



3 30 



3-68 



112 









Mean 1 -16 



The striking distances from which the above ratios are calculated 

 are those obtained from the smoothed curves. 



