produced by the Splashing of Mercury. 



465 



surrounding C and D ; paraffin, which largely reduced these 

 irregularities, was therefore used. The brass tubes were 



Ffc. 1. 



connected to the insulated pole of a battery, the other pole 

 of which was earthed, and the ions were driven over to C 

 or D, originally earthed and connected to the electrometer. 



As a preliminary investigation, it was deemed advisable 

 to test if the ionization of the air was the same if the mercury 

 struck the drop-plate in an electrified condition or not. If 

 the dropper and the splash-plate are both earthed the mercury 

 might be electrified in its passage through the air and so 

 reach the plate in a charged condition. To test this, the 

 dropper was placed above a long narrow cylinder provided 

 w r ith a hole just large enough for the stream to go through 

 without splashing. The cylinder and leads were screened by 

 an earthed outer cylinder. If any charge is given to the 

 mercury on passing through the air, it will be carried in to 

 the cylinder, the equal and opposite charge remaining in the 

 air above. The ionized air-charge and the charge on the 

 plate will be of equal amounts and opposite in sign, so that 

 any current given to the electrometer will be due to air 

 friction. Various heights were tried but no definite evidence 

 of electrification was found. 



Next the dropper was insulated on a block of wax, the 

 splash-plate was earthed, and the currents were examined on 

 the second electrode of the final apparatus. The current 

 was taken when the dropper was earthed. Then the dropper 

 and the mercury were charged to voltages varying from 

 — 390 to +390. Both positive and negative currents were 

 examined, but no definite variations were found in the 

 ionization currents. Thus in the after-work no variation of 



Phil. Mag. S. 6. Vol. 20. No. 117. Sept. 1910. 2 I 



