Intelligence and Miscellaneous Articles. 159 



is on the Letsebo river. West of the Drakensberg coal occurs at a 

 lower level. 



March 22.— Prof. T. G. Bonney, D.Sc., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. "On Rhytidosteus capensis, Owen, a Labyrinthodont Amphibian 

 from the Trias of the Cape of Good Hope." By Sir Richard Owen, 

 K.C.B., F.R.S., F.G.S. 



2. " On the Occurrence of Antelope-remains in Newer Pliocene 

 Beds in Britain, with the Description of a new Species, Gazella 

 anglica." By E. Tulley Newton, Esq., F.G.S. 



3. " A Comparative and Critical Revision of the Madreporaria of 

 the White Lias of the Middle and Western Counties of England, 

 and of those of the Conglomerate of the Base of the South- Wales 

 Lias." By Robert F. Tomes, Esq., F.G.S. 



T 



XXI. Intelligence and Miscellaneous Articles, 



ON THE ELECTROLYSIS OF SOLID GLASS. BY E. WARBURG. 

 HE facts described in this paper may be summarized in the 



following manner :- 



In the electrolysis of lime-soda glass heated to about 300° 

 between mercury electrodes, a badly conducting layer of silicic acid 

 is formed on the anode side of the glass, which soon reduces the 

 strength of the current to a fraction of its original value. This 

 layer has a greater or less thickness, according as a greater or 

 lesser electromotive force has acted in the circuit in a definite time. 

 It is visible, showing the colours of thin plates, diminishes the 

 surface- conductivity of the glass in the cold to a fraction of its 

 original amount, and at a high temperature, when the mass of the 

 glass has become a conductor, it acts like the dielectric of a con- 

 denser whose coatings are the conducting mass of the glass, and the 

 mercury of the anode. The capacity of this condenser was found to 

 be independent of the difference of potentials of the coatings, between 

 1 and 20 Bunsen's elements ; and for a square centimetre of the 

 glass used it varied from O021 to 0*041 microfarad, according 

 as the layer was formed by 30 or 15 Bunsen's elements acting for 

 several hours at 300°. 



The formation of this layer may be avoided by using sodium 

 amalgam as anode ; the result of the electrolysis may then be quan- 

 titatively determined. In this a quantity of sodium is given off at 

 the kathode and absorbed at the anode, so that the weight of the 

 glass does not vary ; the weight of the sodium is chemically equi- 

 valent to the weight of the silver which is deposited at the same 

 time in the silver voltameter. During electrolysis the glass remains 

 perfectly clear ; and it was found that all the properties of the 



