Allen — The Electrical Resistance of Porcelain. 



307 



Table 11. 



Sample G. 



Thickness, 0'22 em. 



Table 10 gives the results obtained for sample G, using mercury for the 

 -contact surfaces, and Table 11 when using graphite in place of mercury. The 

 operation is necessarily slower with the inferior conductor, and its liability to 

 blow about and bridge the contact surfaces makes careful manipulation and 

 precaution very essential. The results obtained in the two cases do not 

 •differ from each other to an exceptionally large extent. 



Fig. 6 shows that sample G has a comparatively much higher insulation 

 resistance than the preceding samples. 



Table 12. 



Sample H. 



Thickness, 016 cm. 



