174 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Table III. 
Curve for Cathode No. 3. 
A= - 8-461, B = ’00005, C = -0100, D= - -02962. 
The constants were calculated as above from the values of the polarisation 
at the times 0‘3, 0’4, 0 - 5, and 06 mins. 
Time 
Polarisation. 
T 
(in mins.). 
Observed. 
Calculated. 
Difference. 
1 
1 *2 
155 
131 
24 
i 
r, 
200 
158 
42 
l 
3 
205 
191 
14 
1 
9 
210 
210 
0 
2 
7? 
220 
223 
-3 
5 
6 
230 
232 
-2 
l 
240 
239 
1 
ii 
258 
251 
i 
disagreement for large and for small values of the time. For the larger 
values of the time the disagreement is of no moment, for they are beyond 
the limit within which the formula was assumed to hold. 
In the case of the small values of the time large differences were to be 
o 
expected, because time was observed by means of an ordinary watch, and 
also because the curves are exceedingly steep for these values of the time. 
Comparatively small errors in determining the time of starting the current 
would produce large differences of uniform sign (see Tables I. and III.), while 
small errors in determining 1 the times of the observation of the earlier 
stages of polarisation would give rise to differences of variable sign (see 
Table II.). Throughout the range which can fairly be tested by these 
experiments the agreement is fairly good. 
In the original form of Wiedeburg’s formula there are only three 
constants, whereas I have used four. These must therefore be con- 
nected by some relation, which can readily be shown to be AC = D, by 
using the values of A, B, C, and D obtained on page 170. In none of my 
three sets of constants does this relation hold ; the product of AC being 
in all cases just about three times as great as D. This seems to indicate 
that the points used for the determination of these constants have been 
taken too far along the curve, i.e. at places where Wiedeburg’s formula 
may no longer be applicable. It would be possible by repeated trials to 
find a range of points which would furnish such values of the constants as 
to satisfy the condition AC = D, but as these observations are merely 
