Proi. Riess on Electric Pauses. 



261 



mon oxygen ; but at a higher temperature it changes, partially at 

 least, into peroxide, which unites with the remainder of the oxide 

 to form red lead, and the oxidizing actions of the peroxide of lead 

 show clearly enough that one equivalent of oxygen in this com- 

 pound is in the ozonized condition. We may therefore ascribe 

 to oxide of lead also the property of transforming, under appro- 

 priate circumstances, into 0, and of being the carrier of this O. 

 I have ah-eady shown, years ago, that the oxygen ozonized by 

 electricity or phosphorus combines v.'ith PbO to form peroxide 

 even in the cold. 



[To be continued.] 



XXXIX. On Electric Pauses. By Professor Riess*. 



A SINGULAR effect connected with the discharge from 

 the conductor of a machine was observed by Gross, and 

 described under the name of ''Electric Pauses," in the j^ear 

 1776. The same effect was accidentally observed by Nairne 

 during his investigations on the best form of lightning conduct- 

 ors, and described in Mutton's ' Abridgement of the Philosophical 

 Transactions' for 1778. The phsenomenon consists in the dis- 

 appearance and reappearance of the electric spark when the 

 discharging distance is gradually augmented. Prof. Riess has 

 recently repeated these experiments, and describes the following 

 arrangement made use of by himself as an easy and sure means 

 of obtaining the effect referred to. 



To the conductor of an electric machine a brass arm was 

 screwed, and united by a ball-and-socket joint with a brass bar 

 8 inches long and 2i lines in thickness, which carried at its end 

 a brass ball 1 j^ich in diameter. The arrangement is shown in 

 fig. 1. At the edge of a table a glass rod was fixed which 



Fig. 1. 



carried a metal collar at its top, through which the brass rod 

 * Abstracted from Poggendorff's Annalen, vol. xcix. p. 



