I 20 Determination of the law of electric force 



The hemispheres were fixed within their frames in such manner that 

 when the frames were brought near together the edges of the hemispheres 

 touched each other all round as near as might be, so as to form a complete 



c 



Fig. 12. 



sphere, and so that the inner globe was inclosed within them without 

 anywhere touching them, but on the contrary being at nearly the same 

 distance from them in all parts. 



222] It was also so contrived, by means of different strings, that the 

 same motion of the hand which drew away the wire by which the hemi- 

 spheres were electrified, immediately after that was done, drew out the 

 wire which made the communication between the hemispheres and the 

 inner globe, and immediately after that was drawn out, separated the 

 hemispheres from each other and approached the stick of glass Tt to the 

 inner globe. It was also contrived so that the electricity of the hemi- 

 spheres and of the wire by which they were electrified was discharged as 

 soon as they were separated from each other, as otherwise their repulsion 

 might have made the pith balls to separate, though the inner globe was 

 not at all overcharged. 



The inner globe and hemispheres were also both coated with tinfoil to 

 make them the more perfect conductors of electricity. 



223] In trying the experiments a coated glass jar was connected to 

 the wire by which the hemispheres were electrified, and this wire was 

 withdrawn so as not to touch the hemispheres till the jar was sufficiently 

 charged. It was then suffered to rest on them for two or three seconds 

 and then withdrawn, and the hemispheres separated as above described. 



224] An electrometer also was fastened to the prime conductor by 



