A FURTHER colloquium in the series arranged by the Manchester University Branch of the Association of Scientific Workers was addressed by Dr. T. G. Cowling on December 2, the title being “The Temperature of the Atmosphere”. Dr. Cowling began by describing how the temperature of the lower part of the atmosphere is determined by radiation, convection, and advection (horizontal currents of air and water). The distribution of temperature over the earth's surface varies with the season, and in consequence sudden large fluctuations in temperature due to the passage of air masses are in the British Isles more probable during winter than summer. Turning to the variation of temperature with altitude, Dr. Cowling suggested a possible explanation for the fact that the temperature ceases to decrease at a height known as the tropopause. According to this theory, solar energy is absorbed by ozone in the stratosphere, and in the absence of any gas with strong emission bands in the infra-red, the temperature is increased. Water vapour has broad intense bands in the infra-red, and when it is present tends to keep the temperature low. In considering variations of the temperature in the stratosphere with season and latitude, account must be taken of any variations of the concentrations of gases such as ozone and water vapour, as well as of the intensities of the radiations coming from the sun and earth. During the discussion which followed, Dr. L. Janossy pointed out that the tropopause falls rapidly at the same latitude that shows a marked increase in cosmic ray intensity. Cosmic rays might conceivably produce some ozone, and so account for the higher temperatures over the poles.