45* 



ELECTRICITY. 



iriboboo ot 

 electricity 

 between two 

 KM*, of 



nd in con- 



rVvi 



uily. 



On the dii- 

 trilmtion of 

 electricity 

 between two 



different 

 limrur-, 

 aiul in cwi 



a :. 



Now, as the quantities of electricity before and after 

 Contact, art- )>ro)x>rtioiial to the angles of torsion, it is. 

 very easy to ascertain these quantities. In the first ex- 

 periment the force of torsion, for a distance of 30, 

 was 1*5 before contact, arid 12 after contact; so 

 that the quantity of electricity taken by the large globe 

 will be 14512=133, only 12 being left to the small 

 globe, hence the quantities of electricity possessed by 

 the two globes are as 13:5 to 12, or as 1 1.1 to 1.0. In 

 the same manner it will be found that this is nearly the 

 ratio in the other four experiments. Now, the sin-faces 

 of two globes, six inches and a quarter, and 24 inches 

 in diameter, are in the ratio of 1 .48 to 1.0; hence 

 we may conclude, that the globes ore not charged 



with electricity in a ratio as great as that of their sur- 

 faces. 



In order to find the electrical densities of the two 

 globes, we must divide the ratio of their Mirfai . 

 the ratio of the quantities of fluid which they cou 

 tain, and the quotients by the ratio of the deli 

 Thus, in the present case, the electrical density <;f the 

 small globe will be to that of the great one as 1 ks to 

 11.1, or as 1.33 to 1. 



In this manner Coulomb has obtained the electrical 

 densities for globes of various sizes, and has given the 

 general result of them in the following Table. The 

 mean results were obtained from experiments made 

 by both the methods which we have already described. 



TABLE shewing the manner in ichich the Electrical Fluid distributes itielf bttween ttco Globes of 



different Diameters. 



On the dei- 

 jity of the 

 electricity 

 in different 

 point* of 

 l>gJobef 

 in contact 



PLATE 

 rcxi.v. 



If any two globes, for example, have radii of 1 and 'to 

 inches, then the ratio of these numbers are as 1 to 4, so 

 that the ratio of their electrical densities will be as 1 to 

 130; it being always supposed that when they are se- 

 parated the electricity is distributed uniformly over their 

 surfaces. 



S. On the Density of the Electricity in different Points nf 

 two Globes in Contact. 



In order to determine the density of the electric mat- 

 ter in different points of two globes in contact, Cou- 

 lomb employed the small balance represented in Plate 

 CCXL1V. He placed a small circle of gilt paper?, Fig. 7. 

 four orfive lines in cliameter.at the end of a thread of gum 

 lac cde, fixed to a cylinder of glass or of well baked wood 

 cb, coated with a non-conducting varnish. This cy- 

 linder moves up and down in the hole b of the piece 

 of wood A b, and can be fixed in any position by means 

 of the screw s. In comparing the electricity of any 

 two points, the circle of tinsel on the needU of the 

 balance was electrified, and the circle of gilt paper, after 

 touching one of the points, was put into the balance, 

 and the quantity of its electricity measured as before. 

 The electricity of the second point was determined 

 in a similar manner. The electricity of the first point 

 was again determined, after an interval equal to that 

 between the fir* and second observations, and the 



mean between the two determinations adopted as free 

 from the effects of dissipation. 



Exp. 1. With tn'o equal Globes each 8 Inches in Dia- 

 meter. 



HepuUive force. 



Globe touched at 30 from the point of contact 

 (1 lobe touched at 90 from the jwint of contact 31 

 Globe retouched at 30 from the point of contact (> 

 Globe retouched at <)0 from the point of contact 27 

 Hence taking the three first observations, the density 



at S0 is to that at 90* as 64 to 31 or . . 1 to 4.77 

 Taking the three last, it is to that at 90 as 6 



to 28, or 1 to 4.67 



When ihc 

 two |<lobw 

 re equal. 



Mean 1 to 4.72 



Exp. 2. With the same Globes. 



Repulsive force. 



Globe touched at 60 from the point of contact 21 

 Globe touched at 90 from the point of contact 23 

 (i lobe retouched at 60 from the point of contact 17 

 ( llol>e retouched at 90 from the point of contact 21 

 Hence taking the three fir.-t oli-crvations, the dcmity 



at 60" is to that at 90 as 19 to 23 or . . 1 to 1.21 

 Taking the three last observations, it is as 17 



to 22, or 1 to 1.29 



Mean 1 to 1.S5 



