54 



K. TSURÜTA. 



the usual way, the current in the diagonal was reversed and the 

 resistance again determined. Since the E. M. F. of the thermo- 

 electric couple is very small, amounting only to a few micro-volts, 

 and the above two determinations of resistance do not differ much, 

 the true value of the resistance in question is equal to the mean of the 

 two determinations multiplied by the ratio of the resistances put in 

 the proportional arms. As an example may be cited the following 

 observations made on an annealed soft iron wire 0*5 m.m. in dia- 

 meter : — 



So far as my determinations went, which were made immediately 

 after each series of measurements of the E. M. F., the numerical 

 values obtained were closely of like nature to the above. It may be 

 that the resistance of the iron wire under varying longitudinal tension 

 suffers a corresponding, perhaps regular, variation, but as no law of 

 the variation is discernible from my determinations, and the amount 

 of the variation is always quite small, I think it proper to take the 

 resistance as constant for the purpose of the present investigation. 

 Thus, there being no need of measuring the resistance at each step of 

 loading or unloading the wire, both observations and calculations 

 have become greatly simplified. 



