322 
Proceedings of the Royal Society 
ance of *95 ohms. A battery of four Bunsen cells was found neces- 
sary to produce a current. The following figures show the readings, 
on a tangent galvanometer, of the deflections produced by the cur- 
rents x' + y' and y' respectively : — 
22°-8 23°T 22° c 9 22°-9 23°*1 23°.l 
13°d 13°T 12°-8 13°-0 1 2°*9 13°-1 
This series of readings is one of the most unsteady obtained, and it 
was found on testing that most of the variations might be due to 
alteration of the electromotive force of the battery employed, or to 
alteration of contact at the various junctions of the circuit. The 
next set of figures are values of the ratios - and respectively. 
y V 
1-25 1T9 1-245 1T9 
0-811 0-840 0-846 0-87 
The value of the specific resistance deduced from these observations 
agrees very closely with previous determinations by other methods. 
Evidently the method may be used to investigate the laws of 
variation of polarisation with current density. Eor we have as 
above 
ry=( B + p)x - B y +p l -p 2 . 
And we may put generally 
P = p + L/ (y)l 
where / (y) is some function of the current y, P is the E. M. E. 
required to decompose the electrolyte, and a is the area of the elec - 
trode. Hence, if x — y, we get 
So if a — d we get r = p. If now we make ah — a and adjust the 
currents to equality by altering p, we have 
r = P+ l -ff(y), 
where p is known in terms of p, so that / (y) is determinate. 
Again, either of equations (1) or (2) may be used to find the value 
of p, which is the electromotive force of polarisation produced by 
unit current. 
