PHACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 

 Table "VIII. (IV. Revised). 



41 



With reference to Tables V. and VI. the data for 1901-1903 show a rise 

 of -OOS per cent, for F, -034 per cent, for G, and -Oil per cent, for H, 

 indicating that they are certainly changing coils, the resistance for this 

 period increasing with time. 



From the values recorded 371.5 and 270 we have evidence that Flat 

 has probably remained constant for the period 1894-1901. Also we infer 

 that 264 is not a coil showing very great changes. 



Between the years 1892 and 1898 the differences between Flat and 

 the coils F, G, and H alter by the amounts -018 per cent., -009 per cent., 

 and -023 per cent, respectively. The dissimilarity of these percentage- 

 differences is further evidence that the coils liave changed amongst them- 

 selves in this period. Comparing the amounts with those of the period 

 1901-190.3, they represent quite normal increments of resistance. The 

 balance of evidence in consequence is in favour of the constancy of Flat 

 over the period 1892-1898, and this constancy has therefore been assumed. 



A summarised statement of the platinum -silver coils of the Associa- 

 tion will now be as follows : — 



Table IX. — SlwvAng tJw Percentage-increase in Resistance of B.A. Platlnvm- 



silcer Coils from 1888. 



value 



It will be observed that a number of the coils arc steadily rising in 



The insulation remains good. 



Temperature Corfficients of B.A. Coils. 



Some .special observations have been made in order to obtain tlie 

 temperature coefficients of the coils. These were carried out by keeping 

 the standard coil constant and subjecting the tested coil to various 

 temperatures for twelve or more hours so as to ensure no log, It is 



