“Either spirits of wine, or some fatty substance, such as stearine of coco-nut oil, tallow or blubber” is the fuel described by McClintock as used on his sledge journeys of the last century. Since those days both the type of fuel and its precise method of use have gradually changed with increasing knowledge and experience. In the present instance it is intended to discuss the use of fuel only in so far as it concerns the unsupported sledge party which must attempt to remain as long in the field as is possible on the supplies that it can carry from the beginning. In such circumstances it has always been obvious that the aim must be to reduce the ration of food and fuel to the absolute minimum of weight. The most efficient fuel is clearly that which provides on combustion the greatest amount of heat per unit weight, though some compromise must be made between the greatest “efficiency” in this sense and questions of safety and convenience. For many years this compromise has resulted in the general use of pressure stoves (such as the Primus) burning liquid paraffin. There is still, however, controversy as to the precise method of use by the sledge party of the small amount of fuel that is carried.