40 



REPORTS ON THE STATE OF SCIENCE. 



relatively lower than when examined by Dr. Fleming, and its value was 

 not, therefore, taken from the chart. 



In 1908 the individual coils were compared with the new mercury 

 standards set up at the N.P.L. and their values found in terms of mer- 

 cury. If we assume that the mean value of the coils A, B, C, T>, E, G, 

 is the same as when Fleming's chart was constructed, we obtain as the 

 resistance of 1 metre of mercuiy, 1 sq. mm. in section, at 0° C, the value 



0-9.5.333 B.A.U., 



an alteration of 20 parts in 100,000 since 1888. 



If, on the other hand, we suppose that the mercury units set up in 

 1908 agree exactly with those constructed in 1888, then the mean value 

 of the six coils in question has altered by 000020 B.A.U. At the 

 present date, assuming as found in 1888, the resistance of 1 metre of 

 mercury, 1 sq. ram. in section, at 0° C. to be 0'95352 B.A.U. , the indi- 

 vidual coils have the values given in Table V., column 3. 



Table V. 



Values of Coils at 16°0 C. in 1883 and 1908 obtained from comjjufison with 

 Mercury Tubes, assumimj the Resistance of 1 Metre of Mercury to be 

 0-95352 B.A. Unit. 



* In Dr. Glazebrook's experiments the terminals of the mercury standards were 

 not exactly at 0° C, and an error of about 4 parts in 100,000 was probably intro- 

 duced because of this. No correction on this score has, however, been applied, as 

 the magnitude of the error is only of the same order as the probable error of the 

 observations. 



The apparent changes in resistance of the coils, together with the 

 alterations in temperature of the coils necessary to produce equal 

 changes in the resistance, are given in Table VI. 



Table VI. 



