Electrification of Air by Water- Jet. 



149 



through the chinks, though we took care to close all chinks 

 in the door by cotton- wool. Also, if the electrifying lamp 

 connected to the electrical machine were placed nearer than 

 3 feet from the door between the two rooms, inductive effect 

 was felt in the small room. 



We therefore adopted an arrangement shown in fig. 1. AA 

 is a large sheet-iron vat 123 centim. in diameter and 70 



Fig. 1. 



To elec broTneber 



To 

 zu-etb&r jivpet 



centim. in height inverted on a large tray BB. By filling 

 the tray with water the air is confined in the vat. The jet- 

 tube of a water-dropper C passes through the centre of the 

 top of the vat. The water- dropper was fixed in its position 

 by a piece of ebonite and melted paraffin poured round it, so 

 that it is insulated from the vat, which is always kept con- 

 nected to water-pipe for earth. By connecting .the tube D to 

 an aspirator the air inside the vat could be replaced by the air 

 of the room through the tube E, which is a metallic tube or a 

 glass tube coated with paraffin both inside and outside of the 

 tube, and filled with cotton-wool. By this arrangement we 

 could easily make electrified air pass through the metal tube, 

 but with the cotton-wool tube the results were discordant, 

 therefore we are not yet in a position to say anything definite. 

 While these experiments were proceeding we came unex- 

 pectedly on an interesting result. It was found that the 

 potential inside the vat, as shown by the water-dropper on the 

 top of the vat, and connected to the electrometer, was always 

 about \ volt positive at the beginning, and gradually changed 

 towards negative till 5 volts negative was reached in about half 



