The electron emission from cathode surfaces changes rapidly with temperature. The difficulty of measuring the true temperature of surfaces such as that of Barium or strontium oxide has led to the development of a comparison method in which two or more materials may be heated under identical conditions. An electron micro-scope system was used to segregate the emission from each material, the current density measurement being made photographically;Curves for Dushman's equation were plotted as a check on the reliability of the method. The apparatus was used to prepare a table of the relative emission obtained from a few compounds of Barium other than the oxide;To make a permanent record of the various "growth" phenomena in the activation process, a technique for taking motion pictures of the fluorescent image was developed.