160 Intelligence and Miscellaneous Articles. 



put in rapid rotation. As these sectors, one of which is connected 

 with another by means of two tinfoil rings, pass in front of the fixed 

 one, positive and negative electricity are alternately driven out and 

 taken up by two suckers, by means of which it can be further used. 

 The concentrating effect of this apparatus, which has not as yet been 

 brought to its greatest perfection, is unmistakeably seen in the spark 

 which can be obtained with it, in its power of charging batteries and 

 jars, and in the development of luminous phenomena in vacuo, in 

 which action it resembles the induction-coil machine. It exerts 

 chemical actions, too, but obviously only feeble ones, like the appa- 

 ratus which twenty years ago (and unknown to M. Holtz) was con- 

 structed solely for this purpose by Mr. Goodman, but without suc- 

 cess. This was essentially constructed on the same principle, but 

 with a different and very disadvantageous application. — Berliner 

 Berichte, April 1865. 



ON THE OPTICAL PROPERTIES DEVELOPED IN DIFFERENT KINDS 

 OF GLASS BY THE PASSAGE OF AN ELECTRIC DISCHARGE. 

 BY M. A. DE LA RIVE. 



In continuation of several experiments on the modifications which 

 the passage of an electric current, either continuous or discontinuous, 

 might produce in the rotatory magnetic power of various liquid con- 

 ductors, I was led to submit to experiment a specimen of crown 

 glass which had been perforated by the discharge of a large Ruhm- 

 korff's coil. I found that this specimen had almost entirely lost 

 rotatory magnetic power, and, on the contrary, had acquired the 

 properties of a crystallized body and of annealed glass. 



Since then, thanks to M. RuhmkorfF, who has kindly placed his 

 large apparatus at my disposal, I have made similar trials on another 

 specimen of crown glass, on one of flint glass, and on one of Fara- 

 day's heavy glass. 



All have given the same result as the first specimen which I tried, 

 as I ascertained by comparing them with similar specimens which 

 had not been submitted to the action of the discharge. 



Hence the passage of a strong electric discharge through trans- 

 parent insulating bodies imparts to these bodies a permanent mole- 

 cular modification of the same kind as that which is produced, but 

 only momentarily, by heat and pressure. The curious circum- 

 stance is, that this modification is not limited merely to the parts tra- 

 versed by the discharge, but extends to the entire mass, provided this 

 mass do not exceed certain limits ; its texture undergoes thus a per- 

 manent change resembling that produced by tempering, and for this 

 the simple shock imparted to the glass by the passage of the discharge 

 is sufficient. — Comptes Rendus, May 15, 1865. 



