When moist clay bodies are heated on one side it is often observed that moisture moves towards the cooler side. This phenomenon has been studied using clay-water mixtures of initially uniform moisture content packed into sealed, vertical tubes, along which a constant temperature gradient is maintained, the tubes having a reservoir of water at constant temperature at their lower, cool ends. Figure 1 shows the moisture distributions obtained after various times in columns of a commercial kaolin (Supreme Kaolin) which contained initially 16-18 per cent. moisture. A “stepped” type of distribution results from the movement of the moisture, the step moving down the column with increasing time.