ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 



59 



The results of these observations are given in the chart,' Plate I. 



The vertical divisions are ten bridge divisions, and the horizontal 

 divisions 0'''2C. In the original chart, which is retained with the stan- 

 dards, the vertical divisions were one bridge division, or -0000498 B.A.U. 



About eleven observations on each coil are recorded in the chart, and 

 in but few cases is the error between observation and the corresponding 

 straight line greater than that which would arise from an error of one- 

 tenth of a degree Centigrade in the temperature of the coil. 



If as above we adopt as the Mean B.A. Unit the mean of the value of 

 the coils at the temperature at which each was said to be originally 

 correct we find that this mean lies on our chart at a distance of 78'3- 

 divisions above the value of Flat at 0°, so that 



Flat at 0°=1- 00390 B.A.U. 



The value given on Fleming's chart is Flat at 0°=1 — -00410 B.A.U., and 

 the difference is within the errors of reading on his chart. 



We have thus the data for finding the resistance of any of the coils in 

 Mean B.A.U. at any temperature between 10° and 20°. 



It remains to compare these results and those of previous observers. 

 We will take Fleming's. observations first, and for this purpose have given 

 in Table IV. the differences in bridge wire divisions between the coils at 

 temperatures of 10° and 20° and Flat at 0°. For the sake of comparison 

 Table II. is repeated. 



Table IV. 



' Note. — The smaller letters in brackets after some of the observations on the chart 

 give the initials of the observer. 



