160 



Specific Inductive Capacity. 



[Nov 17, 



K = 4*82 ; the other had been in the laboratory a long time, and was 

 dried over copper sulphate — 



K = 4-84. 



The result of my earlier experiments for castor oil was 4*78 ; the 

 result obtained subsequently by Cohn and Arons* is 4*43. Palaz. 

 gives 4*610. 



Ether. — This substance as purchased, reputed chemically pure, does 

 not insulate sufficiently well for experiment. I placed a sample 

 purchased from Hopkin and Williams as pure, over quicklime, and 

 then tested it. At first it insulated fairly well, and gave K = 4*75. 

 In the course of a very few minutes K = 4*93, the insulation having 

 declined so that observation was doubtful. After the lapse of a few 

 minutes more observations became impossible. Professor Quincke in 

 his first paper gives 4'623 and 4*660, and 4*394 in his second paper. 



Bisulphide of Carbon. — The sample was purchased from Hopkin 

 and Williams, and tested as it was received — 



K = 2*67. 



Professor Quincke finds 2*669 and 2*743 in his first paper, and 

 2*623 in his second. Palaz gives 2*609. 



Amylene. — Purchased from Burgoyne and Company — 



K = 2*05. 



The refractive (fi) index for line D is 1*3800, 

 fjfi = 1*9044. 



Of the benzol series four were tested : benzol, toluol, xylol, obtained 

 from Hopkin and Williams, cymol from Burgoyne and Company. 



In the following table the first column gives my own results, the 

 second those of Palaz, the third my own determinations of the refrac- 

 tive index for line D at a temperature of 17*5° C, and the fourth the 

 square of the refractive index : — 



H. yU 2 . 



Benzol 2*38 2*338 .... 1*5038 .... 2*2614 



Toluol 2*42 .... 2*365 1-4990 .... 2*2470 



Xylol 2*39 .... — .... 1*4913 .... 2*2238 



Cymol 2*25 .... — .... 1*4918 .... 2*2254 



For benzol Silow found 2*25, and Quincke finds 2*374. 



The method employed by Palaz is very similar to that employed by 

 myself in these experiments; but, so far as I can ascertain from his 

 paper, he fails to take account of the induction between the case of 



* ' Wiedemann's Annalen/ vol. 28, p. 474. 



