Intelligence and Miscellaneous Articles. 



79 



which is, according to circumstances, 70 to 150 times greater than 

 that of the condenser formed by the two plates. The other pole, 

 the external armature of the jar, the movable plate, and the beam 

 of the balance are put to earth. 



The whole apparatus except the scale-pan is placed in a cage the 

 air of which is dried. 



The plates of sulphur and of paraffin are obtained by melting 

 in a mould, the bottom of which is carefully levelled. The thick- 

 ness of the plate is measured by a two-ended screw and a catheto- 

 meter. The distance between the two plates is also measured by a 

 cathetometer. 



The dielectric is placed iu the cage some days before the experi- 

 ment so as to get rid of all traces of electricity. 



The balance being somewhat too lightly tared, and all parts 

 being put to earth, I counterpoise by a weighty. I then electrify 

 the fixed plate, and counterbalance again with a weight P. I put 

 this plate to earth and counterpoise again by a weight p : then 



2 ' 

 The attraction F' is determined in like manner by three operations. 

 I work in the same way with liquids, measuring F' first, and then 

 F so as to avoid evaporation. The thickness of air e' undergoes in 

 this case a slight correction, which consists in replacing the thick- 

 ness ol the layer of air forming the bottom of the vessel containing 

 the liquid by the equivalent thickness of air. 



F 

 In each experiment I calculate the ratio — , and then the cor- 



rected ratio 



E = 



From (1) we should have 



F /e+ke' V 

 r\e + e' ) 



Ve=&. 



The following table, in which e and e' are expressed in centi- 

 metres, F and F' in milligrammes, shows that the values of VR 

 agree with the values of h which I have obtained by means of 

 Coulomb's balance (Comptes Bendus, Nov. 16, 1891). 



The formula (1) is therefore correct ; and particularly in the 



F 



case in which e' can be disregarded, we have — =& 2 . 



Jb 



Dielectric. 



e. 



e'. 



F. 



F'. 



F. 

 JB" 



R. 



Vr. 



k. 



Paraffin, No. ] 



;; no. 2.'.z'. 

 » j' 



Sulphur . 



2-20 



3 : 37 



» 

 3-56 

 204 

 2-60 

 2-77 

 2-28 



0-70 

 066 

 0-61 

 0-68 

 054 

 0-32 

 109 

 0-79 

 0-71 



39-5 



405 



30-5 



23-5 



48-5 



7275 



22 



2625 



19-50 



17-25 

 14 

 9 



7-25 

 9-75 

 18-75 

 11-5 

 13 

 8 



2-29 

 2-89 

 3-39 



r/24 



4-97 

 3-88 

 1-91 

 202 

 2-43 



353 

 438 

 4-51 

 4-42 

 7-27 

 5-39 

 2-78 

 249 

 3-38 



1-88 

 209 

 212 

 2-10 

 2-70 

 2-82 

 1-67 

 1*68 

 1-84 



o 



2 : 6 

 2*3 



1-7 

 1 5 



\v 



Ebonite 



Carbon bisulphide. . . 

 Oil of turpentine ... 

 Petroleum 





