But natural
refrigeration find its best illustration in the arid regions of
the southwest by the use of an olla, which is a vessel made of
porous pottery, a stout canvas bag or a closely woven Indian
basket. A suitable vessel is selected, filled with water and
suspended somewhere in midair in the shade. If it is hung in a
current of air it is all the better, as any movement of the
atmosphere facilitates evaporation. A slow seepage of water
filters through the open pores of the vessel which immediately
evaporates in the dry air and lowers the temperature. The water
in the olla soon becomes cold and if properly protected will
remain cool during the entire day.
The dry air also acts as a valuable preservative. During the
winter, when the weather is cool but not freezing, if fresh meat
is hung out in the open air, it will keep sweet a long time. A
dry crust soon forms upon its surface which hermetically seals
the meat from the air and keeps it perfectly sweet. In the
summer it is necessary to dry the meat more quickly to keep it
from spoiling. It is then made into "jerky" by cutting it into
long, thin strips and hanging them up in the sun to dry. After
it is thoroughly dried, it is tied up in bags and used as needed,
either by eating it dry from the pocket when out on a tramp, or,
if in camp, serving it in a hot stew.
Even the carcass of a dead animal that is left exposed upon the
ground to decompose does not moulder away by the usual process of
decay, but what is left of the body after the hungry buzzards and
coyotes have finished their feast, dries up into a mummy that
lasts for years.
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