476 E. L. Nichols — Electrical Resistance of the 



It was found that specimens containing less than eighty per 

 cent of copper could not be worked without frequent partial 

 annealing. Two such specimens were tested, after rolling and 

 again after subsequent annealing. They showed a negative 

 coefficient after rolling, which may have been due to the pre- 

 vious heating, undergone in the process of working them into 

 the necessary form ; but since they were as nearly in the con- 

 dition of the hard-rolled alloys as it was possible to make 

 them, they have been classified in the table among the hard 

 metals. 



The coefficients of the hard-rolled alloys, including those 

 above mentioned, have been used in the construction of the 

 accompanying curve, (figure 1). Abscissae are percentages of 

 ferro-manganese present in the respective specimens ; ordinates 

 are the changes of resistance for 100° C. It will be seen that 

 the coefficient of the unalloyed copper falls considerably 

 below Matthiesen's standard, and that the addition of small 

 quantities of ferro-manganese produces a further very rapid 



2 4/6 - S'" 10 ,12 > I4.-16^18""2<r:22-:2il--,26-28. 



decrease. With ten per cent of ferro-manganese, the change 

 of resistance is less than one per cent for one hundred degrees. 

 Alloys containing from fifteen to twenty per cent of ferro- 

 manganese possess exceedingly small coefficients, the curve 

 crossing the base line at the point corresponding to eighteen 

 per cent. The curve is intended to represent the variations of 

 alloys which are of the same temper, but it is not possible to 

 determine in how far it does so. Indeed for the entire range 

 from fifteen per cent to thirty per cent the coefficient may be 

 given any value between +'00002 and — *00002, by varying 



