The experimental investigations described in this communication had as their primary object the improvement of the Clark and Weston Cadmium Cells as standards of electromotive force. The older investigations of Rayleigh, Kahle, and Glazebrook and Skinner proved the Clark cell to be very trustworthy, and only within the last few years has any serious attempt been made to displace it from the premier position in which it was placed in 1894. In 1892 Weston introduced the cell bearing his name. This cell contains a solution of cadmium sulphate instead of zinc sulphate, as in the Clark, and an alloy of cadmium and mercury forms the negative pole. As originally specified, the solution was saturated at 4°C., and no crystals of cadmium sulphate were inserted in the cell; under normal conditions there was therefore no change in the concentration for small variations in temperature. When the solution is saturated at all temperatures, i. e. , when solid cadmium sulphate is always present in the cell, the name “Cadmium Cell” has been frequently assigned to it in order to distinguish it from the original form. In this communication the latter cell is the type experimented with, and since it is referred to as the Weston Cadmium Cell in the reports of the International Conference the same name has been adopted by the author.