THE LOCALISATION OF BREAKS AND FAULTS. 



539 



resistance at any temperature of copper, platinum silver, Ger- 

 man silver, and platinoid can be obtained by inspection, also 

 curves for finding the number of cells necessary to give a certain 

 current to line when on bridge connections. Other curves and 

 uses of the device are described in the Electrical Review of 

 August 28, 1903. 



The Author has plotted the same set of resistance observations 



in relation tOj— ^according to Schaefer's law (Fig. 306). The 



vC 

 readings being to scale zero, a straight line is obtained as 



Fig. 305.— The Calculator Board. 



would be expected. The earth current correction has not been 

 applied in this particular test, which accounts for the line not 

 cutting the base at quite the same point as the other curves. 

 In plotting a set of readings in relatioa to this function of the 

 current each reading should be corrected for arth current, as 

 explained on page 420. 



To obtain the reciprocals of the square root or one point three 

 root of currents for setting out false or true zero readings, tables 



