92 Mr. J. J. Waters ton on some Electrical 



charged positively, becomes excited negatively on surface next 

 the flame. 



e. Discharge occurs to the same extent with small screen as 

 without it, but much slower. 



/. If the screen is comparatively large, there is little or no 

 discharge if the flame and excited body are on opposite sides and 

 near the centre of the screen; but if near the edge, the discharge 

 goes on the same as if the screen were small. 



Analysis of the Magic Pane. 



30. The Leyden jar described in 2. was highly charged, 

 positively inside, negatively outside. The charging knob, rod. and 

 chain being withdrawn, the jar was placed on a cake of sulphur 

 that rested on an insulating stool. Having touched the outside 

 of the jar, the electroscope was held close to it, and the leaves di- 

 verged with negative electricity ; the divergence increased as the 

 electroscope was removed outwards, keeping the same level until 

 a maximum was obtained, after which it diminished. It also 

 diminished to zero when held quite close to the outside of the jar. 

 The divergence of leaves was greatest when electroscope was held 

 near the mouth of the jar, and least when held near the bottom. 



31. The electroscope being fixed in position within a few 

 inches of the outside of the highly-charged jar, the outside coat- 

 ing of the jar is touched, which causes the leaves to diverge with 

 positive electricity. Then watching them, they are seen gradu- 

 ally to close and then gradually to open again with negative. 

 Touching the outside of jar again, the leaves close and open with 

 positive, then slowly close and open with negative, as before. 



32. The same experiment as 31. repeated, except that the 

 mouth of the jar was closed with a cake of sealing-wax. This 

 sealing and closing up of the jar did not prevent the phenomena 

 detailed in 31. from taking place 5 but whether at a slower rate 

 was not remarked. The jar gradually lost the whole of its 

 charge, although the mouth was completely sealed up. 



33. A circular plate of fine red sealing-wax, 6 inches in dia- 

 meter and \ inch thick, was coated with circles of tinfoil 3 inches 

 in diameter. It was then placed upon a 6-inch diameter cake of 

 sulphur strongly excited negative (fig. 13). The top coating of 

 wax cake was then touched (fig. 14) and a spark obtained. The 

 wax cake was then removed (fig. 16), and its lower side presented 

 to gas bead-flame (fig. 17). It was then placed with its lower 

 coating on cap of electroscope. The leaves do not diverge until 

 the upper coating is touched, when they spring out with nega- 

 tive (fig. 18). Reversing the cake and bringing the top coating 

 near, but not touching, the cap of electroscope, the leaves diverge 

 with faint negative; bringing it down to touch there is no diver- 



