1879.] 



Electrical Insulation in High Vacua. 



351 



moved away, so as to keep the same angle between them. It is there- 

 fore evident that the leaves themselves were also charged. 



Fig. 4. 



C 



Fig. 4, C, shows the two positions of the leaves, aa before applying 

 heat to the side c of the tube, and bb after heating the glass at c. 



The tube was now heated on both sides, causing the leaves to 

 come nearer together as shown at fig. 4, D. While the glass was 

 warm the cylinder was raised so that it surrounded the leaves : 

 this caused them to get a little closer together, and they kept in this 

 position, shown at E, after the whole apparatus was quite cold. 



After remaining thus for some time, the cylinder was lowered, and 

 the leaves widened out and took up the position shown at bb, fig. 4, C. 

 They did not return to the position aa, showing that their divergence 

 was now owing to their own mutual repulsion, and not to an attrac- 

 tion of one or other to the electrified glass. 



In December, 1877, I totally immersed one of these exhausted glass 

 bulbs in a vessel of water ; the gold leaves having previously been 

 charged, and standing at an angle of 112° from one another, as at fig. 5. 

 The water was connected electrically with " earth," and the whole 

 was set aside in a cabinet on the 1st of January, 1878. 



At the present time, after having remained in this condition for 

 thirteen months, the leaves form exactly the same angle with one 

 another which they did when they were first put in the cabinet. 



vol. xxvin. 2 c 



