ELECTROMOTIVE FORCE OF POLARIZATION. 51 
were unconnected but the pairs ¢ and d, and f and g connected, the quadrants of the 
electrometer were brought into contact with the electrodes of À. If the pairs d and e, and 
g and h were connected, the quadrants were brought into contact with the electrodes of B 
the same pair of quadrants being brought into contact with the anode of B as in the former 
case with the anode of A. A simple rocking commutator was used for making these 
connections. 
The order of observation was as follows: (1). The equality of the potentials of the 
electrodes of the cells A and B was tested. If the electrodes were found to be at different 
potentials, they had to be brought to the same potential, by being washed or boiled in 
water, acid, or the solution in the cell, or raised to a red heat. (2). If the electrodes of A 
and B were found or were made electrically similar, then & and /, m and », and o and p 
were joined for a short time, 
the electrodes of A and B became polarized. (3). The wires connecting k and /, &c., being 
lifted from the pools, c and d, and f and g were immediately connected by the commutator, 
the deflection of the electrometer due to the difference of potential of A was read off, and 
the time of the reading was noted. The commutator was then rocked and the same 
observations made for B. And so on; series of such observations being made for A and 
B alternately. 
The connecting wires were in most cases so arranged that both cells produced deflec- 
tions in the same direction. In these circumstances, the equality of the polarizations 

a fraction of a second or a few seconds—during which time 
in the respective cells could be easily tested. For if they were equal, the rapid rocking 
of the commutator should produce no motion of the needle of the electrometer or of its 
attendant light spot. This mode of testing did not require the measurement of time. 
The first electrolytic cells which I used consisted of the two compartments of a box of 
plate glass. It was divided into unequal compartments by a glass partition sliding in 
grooves in opposite sides. The electrodes consisted of Platinum foil and were squares with 
sides of about 3 inches. They were all carefully cut of the same size. They were fixed 
by marine glue to plates of glass, two of them on opposite sides of the movable glass par- 
tition, other two on glass plates whose positions near the ends of the box were determined 
by grooves in the sides. The two compartments, A and B, were thus, during the passage of 
the polarizing current, connected not only by the wires passing to m and », but also by the 
liquid filling the space between the movable partition and the sides of the box. With 
this form of cell I obtained no satisfactory results. The polarizations of the compartments 
were generally unequal and their relative strength varied considerably in amount from 
experiment to experiment. After making a considerable number of experiments, I found 
that that cell became always the more strongly polarized which was the nearer to the 
positive pole of the battery. Thus if the current flowed from A to B, A was the more 
strongly polarized; if from B to A, B was the more strongly polarized. 
This reversible effect could be accounted for in two ways: (1). Only a portion of the 
current passes by means of the electrodes on the movable partition; a portion passes by 
the liquid round the edges of the partition. Hence the electrodes at the ends of the box 
are more strongly polarized than those fixed to the partition. Now although the polariza- 
tions of individual plates in an electrolytic cell have been found by Svanberg and Poggen- 
dorff * to be practically the same, they have been found by Raoult and Gaugain to be 

* Wiedemann’s Galvanismus (2d. Ed.) Bd. 1 2 478. 
