WHEN DOES AIR-DRYING TAKE PLACE?--Experiments[13] were conducted with a view to discovering, if possible, the rate at which crepe rubber dries, and the extent of drying during the night under weather conditions such as prevail ordinarily in Malaya. It is to be remembered that, during the day, most drying-houses are fairly open and that the temperature ranges from about 88° F. in the lower rooms to over 100° in the upper rooms (near the roof) when the sun shines. At night, however, there is usually a decided drop in the temperature, and unless it is a very clear night the air is generally saturated with moisture. In addition the drying-house is closed as thoroughly as possible, and we should expect the atmosphere of the house to be laden with moisture from the wet and drying rubber. It would be a just inference, therefore, that the rate of drying during the night would be much less than the rate of drying during the day, and the results of experiments confirm this very fully. One was hardly prepared, however, to find that, under certain circumstances and at a certain stage, the amount of drying is nil; not only so, but it was found under certain conditions that the amount of drying which took place was negative--_i.e._, the rubber weighed slightly more when taken out in the morning than it had weighed the previous afternoon. [13] Rubber Growers' Association, Malaya Local Report, No. 2, 1914. CREPE MAY INCREASE IN WEIGHT.--As an instance of the kind of result obtained a graph is here given of the rate of drying of a batch of pale crepe. This was hung to dry in the top room of a drying-house in which rubber ordinarily dries quickly. The rubber was hung in a good position, with the bulk of output, near a window which was open for some time during the day. In order to restrict the day interval of drying to the actual period in which the sun was likely to be in evidence, the day was taken to begin at 8 a.m. and end at 4 p.m., the night interval covering the remaining sixteen hours. Thus the night interval was twice as long as the period of day drying. The lengths of crepe were weighed carefully at 8 a.m. and 4 a.m., and the average of the several weights was plotted in a graph.