156 Drs. W. De La Rue and H. W. Muller. [Dec. 13, 



Table VI. 

 Two Paraboloidal Points. 



Jji.iVX.JJ . Ill 



volts. 



Striking 

 distance in 

 centimetres. 



SJLXXVi CLLL/C KJL 

 UU LtjlXvXail Ucl 



rtAiif 1 TT\ pf 



L CI1L 11 1 1C L'l C. 



Volts. 



Intensity of force. 



Electro- 

 magnetic. 



Electro- 

 static. 



1,000 



0-0173 



57,866 



5 -79 x 10 12 



193 



2,000 



-0493 



40,568 



4 -06 „ 



135 



3,000 



0-1282 



23,409 



2-34 „ 



78 



4,000 



0-3078 



12,996 



1-30 „ 



43 



5,000 



-5107 



9,790 



0-98 „ 



33 



6,000 



-6845 



8,766 



0-88 „ 



29 



7,000 



0-8496 



8,239 



0-82 „ 



27 



8,000 



1 -0117 



7,908 



0-79 „ 



26 



9,000 



1 -1602 



7,757 



0-78 „ 



26 



10,000 



1 -2913 



7,744 



0-77 „ 



26 



11,000 



1 -3130 



7,785 



0-78 „ 



26 



12,000 



1-5243 



7,873 



0-79 „ 



26 



13,000 



1 6271 



7,990 



0-80 „ 



27 



14,000 



1 -7146 



8,165 



0-82 „ 



27 



15,000 



1 '7961 



8,351 



-84 „ 



28 



15,450 



1 -8500 



8,351 



0-84 „ 



28 



An inspection of the diagram, drawn on a reduced scale from the 

 curves as originally laid down, shows that the curve for approximate 

 planes (slightly convex, to ensure the centres being the most promi- 

 nent) is continuously concave, whereas those for both point and disk 

 and two points are concave only for a certain distance, and then turn 

 off and become convex. Moreover, that the intensity of force per 

 centimetre decreases continuously up to 15,450 volts in the case of 

 planes ; but that, in the case of a point and disk, and also in that of 

 two points, the decrease ceases after a certain potential has been 

 reached, and that then it increases so as to become nearly a constant 

 quantity. Between a point and a disk the potential per centimetre at 

 9,000 volts and beyond is very nearly 9,200; consequently, if the 

 law holds good, to produce a spark 1 decimetre (3*94 inches) long, 

 92,000 volts, one 1 metre (39-37 inches) long, 920,000 volts,* and a 

 flash of lightning 1 kilometre (0 # 621 mile) in length, a potential of 



* To produce a spark between a point and a disk used for example as the 

 dischargers of an induction coil — 



It would require in E.M.F. 

 In length. volts. 



1 inch 23,367 



1 foot 280,400 



1 yard 841,230 



