1904.] 



between Electrically Charged Surfaces. 



341 





Millimicrons. 



"Volts per micron. 



V ^VOlUSj. 



















Earhart. 



Shaw. 



Earhart. 



Shaw. 



408 



11800 





7 





400 



10300 





>■> 





360 



8260 





" 





350 



7960 









344 



336 * 



2950 









312 



2360 









300 



J- / / U 





200 





240. 

 250^ 



1480 









202 



1180 









152 





950 





150 



121 



800 



860 





?j 



106 



590 



700 



650 > 670 







yi 



530 



600 



650> 620 





» 



76 



440 



550 





5 J 



61 



420 



440 





)J 



DKJ 



/tin 



300 



330 >315 





>> 



38 





210 





55 



26 





140 





SJ 



20 





100 







13 5 





95 





il 



6 





50 





>J 



3 





25 





)5 



1 '5 





15 





)> 



0-6 





5 





5) 



0-5 





4> 4 " 5 





J> 



0-2 





3> 2 ' 5 





5) 



Details. 



Previous observers have been careful to have plain or spherical 

 surfaces opposed so that the conditions of discharge should be definite. 

 But when the discharge distance is, as in this case, always less than a 

 micron and sometimes only a few millimicrons, the form given to the 

 surface is of little importance, for in a polished surface there will exist 

 irregularities on each surface of the order of the distance between the 

 surfaces. In that case discharge will occur from a point on one surface 

 to the nearest point on the other surface. I generally used a bead of 

 iridio-platinum (1 mm. diameter), and a plane of iridio-platinum, both 

 highly polished. 



In using high voltage the surface must be repolished after every 

 discharge, but for small voltage (less than 5) the surface will not 



VOL. LXXIII. 2 B 



