708 



RICE 



ART. L 



this is a picture employed by some writers. The original 

 Helmholtz idea would be pictured by a graph such as that in 

 Fig. 15, curved extremely near the beginning and end of the 

 graph, and a straight steep portion between, sharp bends being 

 the rule at both ends. In the straight portion dif/dz does not 

 change, so that d'^^p/dz'^ is zero there and there is no charge; the 

 positive and negative charges are concentrated in extremely thin 

 layers resembling a condenser distribution. The previous 

 graph gives a picture of a practically plane distribution for the 

 positive charge on the mercury surface and a "diffuse layer" of 



f 



Y (Jy^ 



M z 

 Fig. 16 



charge in the solution, such as Goiiy first suggested. Sugges- 

 tions have also been made that there may be a diffuse layer 

 in the mercury also. 



One last picture (Fig. 16) will show that we might conceive q 

 not to be zero, and yet there might exist no difference of poten- 

 tial between mercury and solution, as the graph has risen to 

 the same level as at the beginning. 



