I. On the determination of the specific resistance of mercury in absolute measure

“ On the whole I am of opinion that if it is desirable at the present time to construct apparatus on the most favourable scale, so as to reach the highest attain able accuracy, the modification of Lorenz’s method last described is the one that offers the best prospect of success. Before this is done however, it appears to me important that the value now three times obtained in the Cavendish Laboratory by distinct methods should be approximately verified (or disproved) by other physicists. To distinguish between this value and those obtained for instance by Kohlrausch, by Lorenz, or by the First B. A. Committee, should not require the construction of unusually costly apparatus. Until the larger question is disposed of it appears premature to discuss the details of arrangements from which the highest degree of precision is to be expected.” The above passage, which concludes a paper communicated by Lord Rayleigh to the ‘Philosophical Magazine, a little before the Electrical Congress at Paris, at which the legal ohm was defined to be the resistance of a column of mercury of 1 sq. mm. section and 1060 mm. long, seems not to have met with adequate response in this country. So far as experiments in English Laboratories are concerned the determination of the ohm remains where Lord Rayleigh left it, except for the contribution made by Glazebrook and Fitzpatrick in their re-measurement of the Specific Resistance of Mercury in terms of the B. A. Unit, which is one of the elements in the determination of the Specific Resistance of Mercury in Absolute Measure by Lord Rayleigh’s adaptation of Lorenz’s method.