452 



DE. C. CHREE, EXPERIMENTS ON ANEROID BAROMETERS 



a similar defect in the opposite direction. In these cases the method of least squares 

 would no doubt have given values closer to the mean. 



The closeness with which the data of Tables II. and III. are reproduced by the 

 formulae based on the above values of the constants is shown by Table V., which 

 gives the algebraical excess of the observed over the calculated values. There is, it 

 will be remembered, absolute agreement when x = 'I, '3, '7, and '9. 



TABLE V. Observed less Calculated Values. (Ratios of Differences to Mean 



Difference.) 



There is not a single instance here where the difference between the observed and 

 calculated values represents as much as O'Ol of an inch in absolute pressure. 



For ordinary purposes unless special importance is attached to the phenomena at 

 the two ends of the range the formula 



y = -35 



(2) 



is quite good enough for experiments made on the old plan over any range not 

 shorter than 6 nor longer than 15 inches. 



Position of Maximum Difference, Descending less Ascending Reading. 



10. As illustrating the practical use of (2), let us find where it makes the 

 difference between the descending and ascending readings largest. For this, putting 



we find 

 whence 



2-91cc 2 8'4z + 37 = 



x = '54. 



(3), 



