212 G. Th. Fechner's Justification of the 



disc with the upwards bent wire, proceeding from it, in a 

 small glass, covered it with petroleum up to about half an 

 inch high, and discharged the platinum wire which projected 

 from the petroleum (and which nowhere touched the glass) 

 on to the electrometer, while I held the glass in my hand. 

 The divergence to the side, 'which indicates the negative electri- 

 city, followed in this case quite as constantly, evidently, and cer- 

 tainly as if the potassium had been insulated in the air. I have 

 already mentioned that the counter experiments in this case 

 were not neglected. 



The following modes appear to me still to offer themselves 

 for the explanation of the result of this experiment according 

 to the chemical theory: 



a. Some moisture was brought together with the potassium 

 into the petroleum, the chemical action of which caused the 

 result. 



b. The petroleum was perhaps adulterated and still capable 

 of acting chemically on the potassium. 



With respect to a. this objection has at first sight the ap- 

 pearance of some weight, since it is true that when the po- 

 tassium is brought from the air into the petroleum, we observe 

 during some time a few gas bubbles rise up from the potassium, 

 which undoubtedly are produced by the chemical action of 

 the adhering moisture. But this development of gas soon 

 ceases ; and long after this had entirely disappeared, twenty- 

 four hours afterwards, during which time the potassium con- 

 tinually remained immersed in the petroleum, (I did not ob- 

 serve it for more than twenty-four hours afterwards) I have 

 obtained the electrical signs in the petroleum of quite the same 

 force, as during the development of gas and even in the air ; so 

 that this objection thus completely falls to the ground. 



As to the objection b, the petroleum employed was that in 

 which the potassium had already been preserved for many 

 years without becoming anything more than deprived of its 

 lustre at its surfaces ; while if the petroleum had contained 

 any oxygen, this must necessarily have produced a gradual 

 destruction of the potassium ; and even if the oil had in the 

 beginning contained any oxygen, this would certainly have 

 been consumed during the long preservation of the potassium 

 in it, so that I conceive this second objection also to be com- 

 pletely refuted. 



4. An experiment on which De la Rive appears to lay 

 particular stress, since he refers to it in several places, is the 

 following {Recherch., p. 67.) : 



" I took two zinc plates exactly similar with regard to 

 their dimensions to the brass plates of an ordinary condenser ; 



