170 Comparisons of plates of rosin with disks 



near to the floor as to the ceiling*, I suppose the effect to have been still 

 greater. 



336] In order to find out, if possible, how much the charge of the globe 

 was increased hereby, I made four flat plates of a mixture of rosin and 

 bees waxf, about 4 inches square and -22 thick, and coated each of them 

 with circles of about 1-8 inches in diameter, and compared the charge of 

 each of them separately with that of a circular plate of tin, 9-3 inches in 

 diameter. I then compared the charge of two of these plates together 

 with that of a tin circular plate 18^ inches in diameter, and lastly I 

 compared the charge of all together with that of a circle of 36 inches 

 diameter J. 



337] By a mean of the different experiments it appears that the charge 

 of each of the rosin plates was alike, and that the charge of any one of 

 them was to that of the circle of 9-3 inches as 10-34 to 9'3> that the charge 

 of the circle of i8 inches was to that of two of the rosin plates together 

 as 20-19 to 21-96, and that the charge of the circle of 36 inches was to that 

 of all four plates as 43-75 to 42-06. 



But the charge of the four plates together will not be exactly four 

 times the charge of one plate singly, as some allowance must be made for 

 the charge of the wire connecting their upper surfaces, and, besides that, 

 the charge of the plates when placed close together will not be quite so 

 great as if placed at a distance fron each other . 



in the inner globe, and the attraction of the outer globe on the canal BE is to the 

 repulsion of the inner one thereon as 



i i 

 CD '' I3C' 



and therefore the quantity of redun. fluid in the inner globe is to that which it 

 would contain if the outer globe were away as 



If room was spherical, 16 feet in diameter, globe in middle of it, its charge should 

 be increased in ratio of 1 6 to 15 by reason of undercharged floor, &c. 



* [This is the only indication of the Height of the room. The circles were sus- 

 pended by silk strings from a horizontal bar (Art. 466) 87-5 inches from the floor. 

 By Art. 474 the platform 14 inches high diminished the height of the bodies in the 

 ratio of 2 to 3. Hence the height of the center of the bodies from the floor was 

 42 inches, and the height of the room 4 x 42 inches, or 14 feet. This would agree with 

 the height of the top of the circle of 18 inches being 51 inches from the floor (Art. 472).] 



f These plates are non-conductors of electricity, and may be charged as Leyden 

 vials. The manner in which I made them will be described in the following pages 

 [Arts. 373, 514]. My reason for making them of these materials is that the charge 

 of such a plate is much less than that of a plate of glass of the same dimensions. 



J It must be observed that, in the two last mentioned comparisons, the rosin 

 plates were placed close together and their upper surfaces connected by a piece of 

 wire. 



[Art. 5570 



