492 DR. C. CHREE, EXPERIMENTS ON ANEROID BAROMETERS 



TABLE XLIII. Ratios of Sums of Differences to Sum for Range 30-21 inches. 



The difficulty here is that large variations in the values of I and m have but little 

 influence on the calculated ratios. The differences between the observed and 

 calculated values in Table XLIII. are in no case in excess of reasonable limits of 

 experimental error. The agreement is certainly best for I = '83, m = 1'5 and 

 worst for I = m = 1. 



The variation of the ratio of the difference of the descending and ascending 

 readings- to the mean difference over a range affords a much more sensitive method 

 of determining I and m. The application of this method shows that, for the special 

 experiments, I = m = I is in reality a better choice than I = '83, m = 1'3. The 

 evidence for this conclusion is supplied by Table XLIV. 



TABLE XLIV. Mean Differences between Observed and Calculated Values of Ratios 

 of Differences of Descending and Ascending Readings to the Mean Difference 

 (Experiments 1-24). 



Previous Work Bearing on the Subject. 



47. Of investigations into elastic after-effect, more especially in metal wires, 

 there is an excellent summary in vol. 1 of WINKELM ANN'S ' Handbuch der Physik.' 

 This I studied, having previously read a number of the papers it refers to, notably 

 some by KOHLUAUSCH. Of quite recent papers on the subject I have not seen many, 



