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Placing sleeping bags close together conservesbody heat. A sheet of cloth over all the bags helps. Insulation is necessary between snow and sleeping bag; the wool, down, or feathers are crushed by body weight to a thin layer having little insulating value. Fir boughs under the tent floor shingled in the usual matter are thoroughly satisfactory. Above timberline some sort of mattress is desirable. Mattresses made of wool and kapok provide ample insulation but are bulky. Modern closed cell foam plastics are also bulky but provide much better insulation than air mattresses, where internal air movements can cause rapid heat loss. Open cell foam is also useful but must be placed in waterproof covers to prevent absorption of moisture. A mattress, air or otherwise, 18 by 36 inches, is wide enough to sleep on and long enough to extend from shoulders to hips. Food bags, boots, and clothing may be placed under the head for a pillow; a rucksack, parka, climbing rope, or other insulating material at hand can be placed under the legs and feet. |
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