The electrical resistivity of copper-nickel alloys has been measured at the temperature-range from ordinary to liquid nitrogen temperature and the validity of Matthiessen\u27s rule concerning the alloys having the compositions approaching copper has been examined. The results obtained are as follows. (1) Both resistivity vs. composition curves obtained at 23β and -183β are approximately parabolic. (2) It has been ascertained that Matthiessen\u27s rule does not hold in the case of Cu-Ni alloys adjacent to copper, i. e. dp/dt is not constant with the change of nickel-concentration but changes linearly with it. (3) A plausible explanation based upon the conduction theory of electricity in metals has been given for the deviation from Matthiessen\u27s rule
