308 BELL SYSTEM TECHNICAL JOURNAL 



measurements. The thermocouple reading involves an error of 

 perhaps 1 per cent. The wave shape factor of the calibrating voltage 

 must in general be considered, but in this apparatus the distortion is 

 probably made negligible by the filter. 



The deflections on the tube are not absolutely proportional to the 

 deflecting forces, but since the calibrations are made over approxi- 

 mately the same distances as the hysteresis measurements the error 

 thus introduced must be small. 



Altogether, the probable observational errors may amount to as 

 much as 4 per cent. 



