The spectral research was carried out on the under-water electric discharge machining at various electrodes. The results obtained were as follows :
(1) The spectra generated by electric discharge machining are composed of the electrode materials and there is no spectrum of Hydrogen and Oxygen. The temperature of anode spot is higher than that of cathode spot and the cathode temperature may be lower than the boiling point of cathode material.
(2) From the spectrum and spectral energy distribution curve of Silver Amalgam electrode, it became clear that the vapor pressure of discharge column is the order of several tens atomosphere. If the pressure upon the electrode is higher than the above value, the force on the electrode is not produced by vapor pressure, but caused by other factor.