CHAP, I.] ELECTRICITY AND MAGNETISM. 



33 



the globe and then withdrawn, it will be found that the 

 inside is destitute of electricity. An electrified pewter 

 mug will show a similar result, and so will even a 

 cylinder of gauze wire. 



SO. Blot's experiment. Biot proved the same fact 

 in another way. A copper ball was electrified and 

 insulated. Two hollow hemispheres of copper, of a 

 larger size, and furnished with glass handles, were then 

 placed together outside it (Fig. 1 9). So long as they 

 did not come into contact the charge remained on the 



A 



CALIFO. 



Fig. 19. 



inner sphere ; but if the outer shell touched the inner 

 sphere for but an instant, the whole of the electricity 

 passed to the exterior ; and when the hemispheres were 

 separated and removed the inner globe was found to be 

 completely discharged. 



31. Further explanation. Doubtless the explana- 

 tion of this behaviour of electricity is to be found in 

 the property previously noticed as possessed by either 

 kind of electricity, namely, that of repelling itself ; hence 

 it retreats as far as can be from the centre and remains 

 P 



