454 LORD RAYLEIGH AND MRS. H. SIDGWICK ON THE 
in the circuit until the experiment actually begins. In the preliminary adjustments 
the resistance of the voltameters should be represented by an estimated equivalent of 
wire resistance, and this should not be too large a fraction of the whole. In our case 
the resistance of the three voltameters charged with nitrate solution of 15 per cent. 
w T as a little under two ohms, and the conditions under which we worked would be 
sufficiently imitated by a circuit containing, besides the [4] and the voltameters, an 
extra resistance of 10 ohms. A battery of three or four Gro ye cells would then be 
sufficient for the generation of the current. 
