Anew pyrometer has been constructed to measure the temperature reached during routine burning of Calluneta. The pyrometer is based on a series of heat-sensitive paints, known as Thermocolors, manufactured by Badische Anilin and Soda Fabrik, A. G., Ludwigshafen am Rhein. A stripe of each member of the series is painted on a thin piece of mica; thereafter, two of these are bound together with thin iron wire, the ends of which can be adjusted to fix the pyrometer in the soil, or attach it to a plant The possible range is from 40[degree] C to 1600[degree] C, with an accuracy of [plus or minus] 5[degree] C. The maximum temperature which has been recorded at ground level is 840[degree] C. In the majority of successful fires, temperatures at the soil surface are about 400[degree] C. The temperature 20 cm. above ground may be more than 500[degree] C higher than that at the soil surface. The amount of heat generated is related to environmental factors, particularly wind, rather than to the composition of the vegetation. The temperatures experienced by the perennating organs of plants are much lower than those cited above, due to the protection afforded by members of the ground stratum and by the soil. The magnitude of the "insulation" varies according to the soil type or composition of the ground stratum. For example, 1 cm. below the surface of an efficient "insulator" the temperature is frequently 400[degree] C less than that at the surface, during burning. This is obviously significant in relation to regeneration.