In field experimentation the effects involved can often only be satisfactorily evaluated on the basis of dry matter yield. The size of plots usually renders the drying of the whole produce impracticable; this necessitates the determination of dry matter content by means of sampling. Since it is essential, on statistical grounds, that each plot should be separately sampled, an experiment may entail the determination of a large number of dry matter percentages. Agricultural produce is generally bulky and subject to fermentation, and therefore apparatus of a larger capacity than that usually found in laboratories is required. In the past much use has been made of uncovered gas heated hot plates, but these are unsatisfactory. Such hot plates do not lend themselves to accurate control of temperature, nor is uniformity of temperature over the plate easy to attain. It is therefore necessary either to run the risk of occasionally burning samples or to dry more slowly than is desirable. Hot plates are very wasteful of heat and the samples are unprotected during drying.