350 



Mr. W. Crookes on 



[Feb. 20, 



leaves permanently charged by means of the excited ebonite. The 

 mica plate was now carefully lowered. As it came between the gold 

 leaves they diverged further apart, and kept so as long as the mica 

 plate was between them. On removing the plate the leaves reassumed 

 their former divergence. This could be repeated any number of 

 times. 



A similar piece of apparatus (fig. 3) was made, only instead of a 

 mica plate coming between the leaves, a mica cylinder, a, capable of 

 being raised and lowered outside the divergent leaves, was employed. 

 I was not able to get entirely concordant results with this, owing to the 

 friction of the mica developing electricity on the inner surface of the 

 glass tube ; but in all cases, when the cylinder was raised until it 

 covered the electrified leaves, it had the effect of diminishing the angle 

 which they formed with each other. 



The following experiments were also tried : — the leaves being 

 separated about 160°, as at fig. 4, A, one side of the tube was slightly 



Fig. 4. 



A 



heated by a spirit flame. The leaf on that side fell to a vertical 

 position, and remained so when all was cold, the other leaf sticking 

 out as before, as at B. This would seem to show that the divergence 

 of the leaves in this case was not so much due to their mutual 

 repulsion, as to an attraction exerted on each of them by the inner 

 surface of the glass tube. The remaining divergent leaf could be 

 slightly lowered when the glass tube above it was warmed with a 

 bunch of cotton wool dipped in hot water. On cooling the leaf rose 

 again to its original position. When this side of the tube was also 

 heated with a lamp, the leaf was repelled down, but not so readily as 

 the other had been, and when the tube got cold, it rose to nearly its 

 former position. This was repeated several times with uniform 

 results. When the leaf was repelled down, the vertical leaf also 



