5 
312 LORD RAYLEIGH AND MRS. H. SIDGWICK ON THE ABSOLUTE 
introduced, the first relating to small alterations in the relative frequencies of the two 
forks, as shown by the number of beats per minute (column VII.), the second to 
variations in the frequency of the standard fork itself, dependent upon change of 
temperature. The temperatures were read by a thermometer which stood between 
the prongs of the standard, and are given in column IX. The corrections necessary for 
reduction to a standard number of beats (16 per minute) and to a standard 
temperature (16°) are tabulated in columns VIII. and X., and the corrected results 
themselves in XI. and XII. In all cases the electric fork vibrated more quickly than 
the standard. 
The degree of accordance in the numbers entered in these columns shows the success 
of the observations, so far as relates to errors of a casual character. In column XIII. 
the results of the positive and negative rotations are combined, so as to exhibit the 
total result of the day’s work. 
The Table, showing the results of the third series, is divided into two parts, 
corresponding to the two positions of the induction coils, before and after reversal 
(§ 19). In each position, it will be seen that two sets of observations were taken 
upon one of the days. Both sets, however, were complete, and in the interval 
between them the resistance coils were all dismounted. A similar precaution was 
taken at least once in each of Series I. and II. 
