330 
PROFESSOR W. G. ADAMS AND MR. R. E. DAT ON THE 
mixture of 1 part of sulphuric acid and 12 of water, the outer cell containing a saturated 
solution of sulphate of copper. This would give an electromotive force of *978 volt. 
The resistance of this cell was very small, and that of the galvanometer with the 10th 
shunt about 650 ohms. The current from this cell was sent through the shunted gal- 
vanometer, and an additional interpolar resistance . of 8‘68 megohms, and produced a 
deflection of 57 scale-divisions. Hence, neglecting the resistance of the cell and of the 
shunted galvanometer as compared with the rest of the interpolar resistance, we have 
for the strength of the current in B. A. measure which, with the unshunted galvano- 
meter, would produce the unit deflection 
C= 57 x 7 8 68 x ~ 10° =1 ' 9767 X 1Q ~ 10 of a K A< unit of current - 
In future all currents will be expressed in scale-divisions of the unshunted galvano- 
meter, and then, whenever it is necessary to find the value of any particular current in 
B. A. measure, all we have to do is to multiply the number of scale-divisions in the 
deflection produced by the current by the factor 1-9767 xlO -10 . 
A series of experiments on polarization were then undertaken with the W. S. plate. 
A current of 37 xlO 3 having passed through it for 10 minutes, gave a polarization- 
current of 45 in the opposite direction. After short-circuiting the selenium for a few 
minutes, no evidence of this polarization-current remained. It does not, however, follow 
that the original polarization was then dissipated, but that, owing to the great resistance 
of the circuit, the electromotive force due to the polarization, having become weakened, 
could no longer send any sensible current through the galvanometer. About a quarter 
of an hour afterwards a current of 33xl0 3 was sent for 10 minutes through the plate 
in the same direction as before, and the consequent polarization-current was 94 in the 
opposite direction. 
Another series of experiments with the same plate gave the following results 
Time. Duration of passage. Strength of current. Polarization-current. 
11.15 a.m 5 minutes. 33xl0 3 — 5 
11.25 „ .... 10 „ „ -12 
11.43 „ .... 15 „ „ -29 
About an hour afterwards the current was sent through the same plate in the opposite 
direction, with the following results : — 
Time. Duration of passage. Strength of current. Polarization-current. 
12.50 p.m 5 minutes. 24*5 X 10 3 — 5*5 
12.58 „ .... 10 „ „ -13-5 
1.11 „ .... 15 „ „ -18 
After the last of these experiments the electrodes of the plate were disconnected from 
