IN the Physical Institute of the Berlin University, Mr. R. W. Wood has been making a series of experiments, most interesting to students of astrophysics, with the object of investigating the relative temperatures at different parts of the discharge in a Geissler tube, with special reference to the stratification phenomena. Wiedemann and Hittorf, and also the theoretical calculations of Warburg, have shown that the temperature of the gas in the positive part of the discharge lies far below red heat, while that of the negative light, according to Hittorf, is at least below the melting-point of platinum. These observations are for the most part corroborated by the experiments of Mr. Wood, who has investigated in this case a fixed part of the discharge in an atmosphere of nitrogen under varying pressures and currents of different strengths. The results obtained by employing hydrogen instead of nitrogen established the fact that, under similar conditions of pressure and strength of current, the heating was only about 11 per cent, of that found in the former case. It was found difficult, however, to keep a steady current with this gas.