It is commonly believed that fats, oils and grease are good non-conductors of heat and if placed on the clothes or on the skin help to keep one warm. There was never a greater fallacy, for it is common experience of polar explorers that the reverse is the case. Circumstances do not permit of regular laundrying or even of regular hot baths, and situations are not rare at this work in which men have spent several months without a wash or a change of clothes. After the loss of the _Endurance_ the party had neither for a year. The clothes inevitably became greasy, especially about the elbows and thighs. The cold could be felt “striking through” the greasy parts. It was often necessary to kill and cut up seals. In the process the left hand grasped the blubber and became very greasy, whilst the right hand, which wielded the knife, very largely escaped. Usually it was possible only to wipe with snow, which had little effect to remove the grease, before replacing the hands in mitts. Subsequently the left hand felt colder and was more liable to frost-bite. Socks which have been worn for some time and become slightly greasy are less warm than clean, dry socks. There are socks of a type manufactured by certain firms which have been deliberately imbued with grease to make them warmer. The wearing of them produced the opposite effect. During the war I made experiments upon myself and with troops, in which two stretcher-bearers massaged the feet of each man, the left foot with whale oil and the right by rubbing only. Both were done at the same time and for the same length of time. The results were greatly in favour of the dry rubbing. I collected also a number of socks which had been worn (and were therefore greasy) and dried them thoroughly. I acquired some absolutely new socks, and issued one dry, greasy sock and one new sock to each man. Evidence in this case was not unanimous, but was numerically in favour of the clean sock. The conclusion is that oils and grease are of small value for protection against cold and should as far as possible be avoided.