152 



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



two points, and the disk was 1^- inch [3'334 centims.] in diameter. 

 The two planes nsed were 1 T 5 ¥ inch [3*334 centims.] in diameter. 



As the points, particularly the negative, are deformed at each dis- 

 charge, the precaution was taken to touch up the point after each 

 discharge in the shaping-tool, screwed to the mandril of the lathe, 

 mentioned in Part I of our researches,* and thus to restore it to a 

 true paraboloidal form. 



The folio wins; results were obtained between: — 



Table I. 

 Two Disks. 



Striking distance. 



Cells. 



( 



Inch. 



Centim. 



12,000 



'148 



-3759 



13,000 



0-160 



-4191 



14,000 



0-181 



'4597 



15,000 



0-198 



-5029 





Table II. 







A Point and a 



Disk. 





Striking distance. 



Cells. 



r 



Inch. 



Centim. 



1,000 



-0055 



-0140 



2,000 



-0240 



-0610 



3,000 



-0600 



-1524 



4,000 



-0950 



-2413 



5,000 



-1700 



-4318 



6,000 



-2300 



-5842 



7,000 



-2770 



-7039 



8,000 



-3450 



-8762 



9,000 



-3900 



-9906 



10,000 



'4340 



1 -1023 



11,000 



-4780 



1 -2141 



12,000 



-5200 



. . 1 -3208 



13,000 



-5680 



1 -4427 



14,000 



-6090 



1 -5468 



15,000 



-6580 



1-6713 



* " Phil. Trans.," Part I, toI. 169, p 



. 79, separate copy p. 25. 



