aUfi, 



THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Aet. XXXYI. — The Electrical Resistance of Stressed Glass,' 

 by Carl Barus. 



The thermal relations of the resistance of glass, originally 

 studied by Buff,* have more recently been made the subject 

 of research in memoirs by Beetz,f Foussereau,:}: Perry,§ Thos. 

 Gray,|| and others. Warburg' sT experiments, however, throw 

 new light on the inquiry, by showing that the apparent polar- 

 ization evoked by the passage of current, is due to a layer of 

 non-conducting silica depositing at the anode. If this be con- 

 tinually dissolved by an electrode of sodium amalgam, the 

 apparent polarization is so far removed that an almost constant 

 current may be kept up indefinitely. If the film be not 

 removed, conduction soon ceases and the glass behaves like a 

 condenser of measurable capacity. 



The effect of temperature on the conductivity of glass has 

 thus been mapped out with considerable detail, and it will be 

 superfluous to add new data in the following paper. I pur- 

 pose therefore to confine myself narrowly to the effects of 



* Buff: Lieb. Ann., xc, p. 257, 1854. 



f Beetz: Pogg. Ann., Jubelband, p. 23, 1874. 



X Foussereau: Journ. de phys., II, xi, p. 254, 1883. 



§ Perry: Proc. Roy. Soc, xxiii, p. 468, 1875. 



|| T. Gray: Proc. Roy. Soc, xxxiv, p. 199, 1883. 



•fi" Warburg: Wied. Ann., xxi, p. 622, 1884; ib., xxxv, p. 455, 1888. 



Am. Jour. Sci.— Third Series, Vol. XXXVII, No. 221.— Mat, 1889. 

 22 



