1895.] Electrification of Air, $-c., by bubbling through Water. 341 



After curve (4) was obtained the aspirator was worked continu- 

 ously for twenty-five Lours, and then curve (5) was obtained. 



10. At the end of twenty-three days of October and November 

 1894 ( 8, 9 above), when the air inside the vat must have been 

 fairly free from dust, and when the water-dropper of itself was giving 

 little negative electrification, we bubbled air into it by a forked tube, 

 one end of which was connected to a bellows, and three other open 

 ends were below the water inside the vat. In five experiments thus 

 made two on November 7, two on November 8, and one on Decem- 

 ber 17 an average negative electrification of 5 volts in twelve 

 minutes was obtained. 



11. We now arranged a U - ^ u ^ e with pure water in it (fig. 4) 

 outside the vat. Air from the bellows bubbled through the water 

 in this U> an( i was carried thence by a block-tin pipe into the 

 vat without any further bubbling. Observations by the quadrant 

 electrometer, while the water-dropper was running and the bellows 

 worked, gave us measurements of the varying state of the electrifica- 

 tion of the air in the vat. The average of fifteen experiments gave 

 a negative electrification of the air in the vat of 8J volts in 25 



CURVK 8. 



