Apparatus for experiment 'with globes \ 1 9 



219] I took a globe 12-1 inches in diameter, and suspended it by a 

 solid stick of glass run through the middle of it as an axis, and covered 

 with sealing-wax to make it a more perfect non-conductor of electricity. 

 I then inclosed this globe between two hollow pasteboard hemispheres, 

 13-3 inches in diameter, and about -fa of an inch thick, in such manner 

 that there could hardly be less than & of an inch distance between the 

 globe and the inner surface of the hemispheres in any part, the two 

 hemispheres being applied to each other so as to form a complete sphere, 

 and the edges made to fit as close as possible, notches being cut in each 

 of them so as to form holes for the stick of glass to pass through. 



By this means I had an inner globe included within an hollow globe 

 in such manner that there was no communication by which the electricity 

 could pass from one to the other. 



I then made a communication between them by a piece of wire run 

 through one of the hemispheres and touching the inner globe, a piece of 

 silk string being fastened to the end of the wire, by which I could draw it 

 out at pleasure. 



220] Having done this I electrified the hemispheres by means of a 

 wire communicating with the positive side of a Leyden vial, and then, 

 having withdrawn this wire, immediately drew out the wire which made 

 a communication between the inner globe and the outer one, which, as 

 it was drawn away by a silk string, could not discharge the electricity 

 either of the globe or hemispheres. I then instantly separated the two 

 hemispheres, taking care in doing it that they should not touch the inner 

 globe, and applied a pair of small pith balls, suspended by fine linen threads, 

 to the inner globe, to see whether it was at all over or undercharged. 



221] For the more convenient performing this operation, I made use 

 of the following apparatus. It is more complicated, indeed, than was 

 necessary, but as the experiment was of great importance to my purpose, 

 I was willing to try it in the most accurate manner. 



ABCDEF and AbcDef (Fig. 12) are two frames of wood of the same 

 size and shape, supported by hinges at A and D in such manner that each 

 frame is moveable on the horizontal line AD as an axis. H is one of the 

 hemispheres, fastened to the frame ABCD by the four sticks of glass 

 Mm, Nn, Pp, and Rr, covered with sealing-wax, h is the other hemisphere 

 fastened in the same manner to the frame AbcD. G is the inner globe, 

 suspended by the horizontal stick of glass 5s, the frame of wood by which 

 Ss and the hinges at A and D are supported being not represented in the 

 figure to avoid confusion. 



Tt is a stick of glass with a slip of tinfoil bound round it at x, the place 

 where it is intended to touch the globe, and the pith balls are suspended 

 from the tinfoil. 



