This is a
frame of mind in which few great journeys have been successfully
accomplished; and an explorer who cannot divest himself of it, may
suspect that he has mistaken his vocation.
It is a common idea among men who are preparing to travel for the first
time, that all the bed-clothing about which they need concern themselves,
is a sufficiency to cover them, forgetting that a man has an under as
well as an upper side to keep warm, and must therefore have clothing
between him and the earth, as well as between him and the air. Indeed, on
trying the experiment, and rolling oneself up in a single blanket, the
undermost side in a cold night is found to be by far the colder of the
two. The substance of the blanket is compressed by the weight of the
sleeper; the interstices between its fibres cease to exist; and the air
which they contained and which is a powerful non-conductor of heat, is
squeezed out. Consequently wherever the blanket is compressed, its power
of retaining the heat of the sleeper is diminished. Soft fleecy
substances, like eider-down quilts, which are extremely warm as
coverlets, are well-nigh useless as mattresses. There is another cause
why a sleeper requires more protection from below, than from above: it is
that if the ground be at all wet, its damp will penetrate through very
thick substances laid upon it. It will therefore be clearly understood
that the object of a mattress is not alone to give softness to the bed,
but also to give warmth; and that if a man lies in a hammock, with only
the hammock below, and blankets above, he will be fully as much chilled
as if the arrangement had been reversed, and he had lain upon blankets,
with only the hammock as a sheet to cover him.
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