1894.] 



On the Electrification of Air. 



89 



side of the vat, and left so with its sharp point unchanged in its 

 position inside the vat during all the observations. 



9. Curve 1. February 8, 1894. The friction-plate machine was 

 turned positive for half-an-hour. Ten minutes after the machine 

 stopped the water-dropper was filled and joined to one pair of 

 quadrants of the electrometer, while the other pair was joined to the 

 case of the instrument. The first reading on the curve was taken 

 four minutes afterwards, that is fourteen minutes after the machine 

 stopped running (18 volts.). 



\5 20 25 30 55 

 Time in m,in,u,Ces 



40 



Curve 2. March 3, 1894. The friction -plate machine was turned 

 jositive for five minutes. The water-dropper was filled and joined 

 the electrometer immediately after the machine stopped turning. 

 spot was off the scale, and nine minutes elapsed before it 

 appeared on the scale. The first reading on the curve was taken one 

 minute afterwards, or ten minutes after the machine stopped turning 

 (36-25 volts). 



Curve 3. March 12, 1894. A Voss induction machine was joined 

 the charging wire, and run by an electric motor for 4 hours 

 19 minutes. A test was applied at the beginning of the run to 

 lake sure that it was charging negatively ; and a similar test when 

 it was disconnected from the charging wire in the vat showed it to be 

 till charging negatively. The water-dropper was joined to the electro- 

 leter, and the spot appeared on the scale immediately. The first 

 sading on the curve was taken half a minute after the machine was 

 jonnected (30' 65 volts). 



