XIV. On the specific resistance of mercury

Of late years several determinations of the electrical resistance of mercury have been made, and the differences between the results arrived at have been greater than would be expected at first sight from the nature of the observations involved. The results of the experiments have been expressed either in terms of theohm (109 absolute C. G. S. units) or of the B. A. unit, which, according to the determinations of Lord Rayleigh and one of the authors of this paper (R. T. G.), is equal to ·98667 ohm. In the case of Lord Rayleigh’s observations, a direct comparison was made between the mercury unit and the original B. A. standards. Other observers have constructed copies of their mercury resistances in German-silver wire, which have been compared with the B. A. standards at the Cavendish Laboratory by one of us, or have compared their tubes directly with copies in platinum-silver wire of the B. A. units which have been sent from Cambridge after careful testing. The result of these various comparisons of recent years is as follows, and may conveniently be put in tabular form, giving the value in B. A. units of the resistance of a column of mercury 1 metre long, 1 square millimetre in cross section, at 0° Centigrade.