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seep through the material. Eventually, less and less water would escape as the bag's
fibres expanded, making it virtually watertight.
Evaporation from the exterior
of the bag absorbed heat as some of the water was converted
to vapour.
The evaporation kept the drinking water cooler than the surrounding
air. To illustrate, think of when the human body becomes overheated
and is cooled by the evaporation of sweat.
The lever on the side of the drinking cap
was pressed downwards to secure the cap tightly to
the bag.
Even today, canvas drinking water bags are used in various
parts of the world because of their low-cost effectiveness.
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