In our last communication (read July 2, 1894) we gave the broad results for three nickel tubes of various bores (see vol. XX. p. 296). In these experiments the screw stopper through which the capillary glass tube passed was made of brass. This brass stopper was used because of the comparative difficulty of working nickel. We were led, in the course of some tentative experiments, to use this brass stopper with one of the steel tubes. Now, in the earlier experiments with the iron and steel tubes, we had used an iron stopper. We were hardly prepared, however, to find that the mere substitution of a brass for an iron stopper should produce such a marked effect, not only on the amount of change of volume in given magnetic fields, but also on the manner in which the volume change varied as the field increased or decreased steadily.