﻿the Electrification of Air. 



227 



showed the electrification which it had on the other side of 

 the chink, whether that was the natural electrification of the 

 open air, or positive or negative electrification produced by 

 aid of a spirit-lamp and electric machine in an adjoining 

 room, has been tried again in the New College with quite 

 corresponding results. It has also been extended to the 

 drawing in of electrified air through a tube to the enclosure 

 represented in fig. 1 of the present paper ; with the result 

 that the water-dropping test indicated in the sketch amply 

 sufficed to show the electrification, and verify that it was 

 always the same as that of the air outside. When the tube 

 was filled with loosely packed cotton-wool the electrification 

 of the entering air was so nearly annulled as to be insensible 

 to the test. 



§ 4. The object proposed for the experiments described in 

 the present communication was to find if a small unchanged 

 portion of air could be electrified sufficiently to show its elec- 

 trification by ordinary tests, and could keep its electrification 

 for any considerable time ; and to test whether or not dust in 

 the air is essential to whatever of electrification might be 

 observed in such circumstances, or is much concerned in it. 



§ 5. The arrangement for the experiments is shown in the 

 diagram (fig. 1). A A is a large sheet-iron vat inverted on 



Fig. 1. 



30 40 50 60 

 ONE METRE 



80 90 100 



a large wooden Iray B B, lined with lead. By filling the 

 tray with water the iiir is confined in the vat. There are two 

 Loles in the top of the vat : one for the water-dropper G ; and 



Q2 



