582 MESSRS. R. T. GLAZEBROOK AND S. SKINNER ON THE 
§ 12. Discussion of Results. 
The mean of the above values is 1*4341 volt at 15° C. The variation from the 
mean is small. The smaller result in Experiment 2 may be due to the unsteadiness 
of the current during the experiment. It will be remembered it rose in value 
suddenly by about one part in 300 during the observations. The result in Experi¬ 
ment 9 is too high. This is, no doubt, due to the fact that the temperature of the 
bottle cell was varying somewhat. The temperature of the bath changed between the 
morning and afternoon observations on August 14 by 0°*5 C. Now, our observations 
have shown us that the E.M.F. of the cell lags behind the temperature when this is 
changing. This lag is due to the time taken in changing the state of concentration 
of the zinc sulphate solution. It is practically certain that on the afternoon of 
August 14 the cell had not reached the steady state corresponding to 18 0, 3, and that, 
therefore, the correction to 15° of "0036 volt is too high. 
It will be remembered that some uncertainty of one or two units is attached to the 
value of Y in Experiment 5, August 10. 
The weighings of the second bowl, No. 2, in Experiments 1, 2, 3, 4 have not been 
used because some small amount of silver was visibly lost in the washings. 
The weighings in the other experiments agree with each other by about one part in 
2000. This agreement is rather less good than that attained in Lord Rayleigh’s 
experiments. It must be remembered that the rate of deposition was about three 
times as great as in his work, and this affects the deposit. The value of the E.M.F. 
thus found needs increasing by about one part in 20,000 for the error of the clock, 
and we thus obtain as the E.M.F. of the standard cell, Rayleigh No. 1, at a tem¬ 
perature of 15° C. the value 
1*4342 volt. 
The English standard legal temperature is 62° Fahr., or 1 6f° C. 
Reducing to this temperature we find the value 
1*4324 volt at 62° Fahr. 
The value found by Lord Rayleigh for his standard No. 1, was 1*435 volt at 15°, 
if we include another figure, the value given in Lord Rayleigh’s Table becomes 
1*4348. Now, his cell No. 4, which is probably our No. 1, was two parts in 10,000 
below his No. 1; and again we have, in accordance with the resolution of the Board of 
Trade Committee, taken *9866 as the value of the B.A. unit in ohms, Lord Rayleigh 
used. *9867. On this account our result needs to be raised by one part in 10,000 to 
compare with his; thus altogether our result needs to be raised by three parts in 
10,000, or by about *0004 volt, to give the E.M.F. of his original cell, No. 1, in his 
units. We thus get for this cell the value 1*4346 volt, as against 1*4348 found by 
Lord Rayleigh, and the agreement is within the errors of the observations. 
