Last summer I communicated a paper to the Society on an Iodine Cell. This cell consisted of a carbon and zinc rod immersed in solution of iodine, in iodide of potassium. I found that iodide of zinc was equally suitable to dissolve the iodine in, as mentioned in that paper. While experimenting with this cell, the idea occurred to me of using it as a secondary battery. When the cell is exhausted, the whole of the iodine has combined with the zinc to form iodide of zinc. If an electric current is passed into this exhausted cell, the iodide of zinc is decomposed, zinc being deposited on the zinc plate, and iodine being set free at the carbon plate. The cell is now ready for use, and will give a steady current, having an EMF of 1·2 volts until the iodine is again combined with the zinc. I tried several experiments on this cell in Newcastle, with a view to testing its applicability to electric lighting as a storage battery.