,, 14 MESSRS. W. R. BOUSFIELD AND W. ERIC BOUSFIELD 



TABLE Il.-Calibration of Thermometer-resistance M 3 . Experiment 34. 



figures in the first column give the temperature of the contents of the calorimeter, 

 those in the second give the values of m 2 , that is to say, the readings of the scale of 

 the thermometer tube of the resistance. The readings in the third column give the 

 resistance (including the leads amounting to about 0'14) as measured in "bridge 

 ohms " on the bridge, and those in the fourth column give the resistance in " bridge 

 ohms " calculated from the formula 



The fifth column shows the difference between observed and calculated values. 

 This difference covers both errors of observation of the thermometer scale and casual 

 errors from point to point in the bridge coils. The maximum single error is of the 

 order of 1 in 20,000, whilst the mean error is less than 1 in 50,000. The result 

 shows that the bridge was in sufficiently good working order, and that the resistance 

 of M a could be deduced from the graduation readings by means of the formula with 

 the order of accuracy required. The corrective factor to reduce " bridge ohms " to 

 international ohms was found to be on this occasion in measuring 9 ohms 1 '000 13 

 and for 10 ohms 1 '00015. Taking the factor as T00014, this gives by multiplication 

 the value of M 2 in international ohms as 



M 8 = 9'37 09 + 0' 



The constant in this formula includes the wire leads to the bridge and also the 

 large mercury leads of the heater. 



