Contact Tlieory of Galtianhm. 207 



It would then in this respect occupy the place of the layer 

 of varnish of the condenser. What however could, according 

 to the view that the developed electricity depends on che- 

 mical action (which can least of all take place at the sur- 

 faces of contact), hinder the transference of the condensed op- 

 posed electricities into one another, and allow of the con- 

 densation even taking place ? Neither can it be a layer of air 

 or of oxide placed between the two, since this must for the 

 same reason oppose itself to the separation of the two elec- 

 tricities; further, such a layer must then also appear as a 

 hindrance to the transfer to the electrometer, where the at- 

 traction for the opposed electricity does not even support the 

 transition. In the mean time De la Rive has mentioned se- 

 veral experiments, which were to prove in a direct manner, 

 that contact, without contemporaneous chemical action, was 

 incapable of developing electricity. We will at present follow 

 him in these experiments. 



2. Already, some time ago, De la Rive had published some 

 experiments, which he now again brings in support of his 

 view {Recherch., p. 57), according to which the signs of elec- 

 tricity, produced by two plates in contact in common air, no 

 longer appear in a vacuum and in dried air. Nevertheless it 

 is evident from the manner in which he performed these ex- 

 periments, that their negative result is rather owing to his 

 having connected the condenser made use of with the earth, 

 by means of perfectly dried wood : now every one may con- 

 vince himself that even in performing this experiment in com- 

 mon air the condenser under these circumstances refuses its 

 services. Besides, PfafF has already previously refuted these 

 experiments experimentally, and with regard to further ob- 

 servations on this point I may refer to p. 20 of his work. 



3. De la Rive, previously, in another place, and lately in 

 his Recherch.f p. 60, has made the following experiment of 

 importance. 



" A piece of potassium or sodium was fixed in a solid manner 

 by one of its ends to a platinum forceps, while the other extremity 

 was held by means of a wooden forceps, or what was better, an 

 ivory one. If, after having well brightened it, it is surrounded 

 by very pure oil of naphtha, [steinbr\ and the condenser be 

 touched with the end of the platinum forceps, no electrical sign 

 is observable ; while if the naphtha oil is taken off" and none re- 

 main adhering to the metal, this is observed to oxidate rapidly 

 by the contact of the air, and the electricity indicated by the 

 electroscope is of the most lively kind. The condenser is 

 scarcely necessary to render it perceptible. If sometimes 

 some indications of electricity are obtained when the potassium 



