On the Variation of the Electrical Resistance of Glass, fyc. 207 



Fig. 2. 



Allowing the lime, magnesia, &c, to replace one equivalent of lead 

 oxide, this glass very nearly agrees with the above theoretical com- 

 position. This therefore ought to be an excellent glass, and so it turns 

 ont to be electrically. So far as these results go then, the evidence is 

 in favour of an exact chemical compound for a glass of low con- 

 ductivity. 



In the following table, the resistances at 60° C. of numbers of 

 different specimens of lime glass are given, together with their 

 densities. The first column tells the kind of vessel experimented on ; 

 the second the resistance in ohms of a cubic centimetre, and the 

 third the density. 



