50. Another instance more strictly mechanical occurs in some
countries where fuel is expensive, and the heat of the sun is not
sufficient to evaporate the water from brine springs. The water
is first pumped up to a reservoir, and then allowed to fall in
small streams through faggots. Thus it becomes divided; and,
presenting a large surface, evaporation is facilitated, and the.
brine which is collected in the vessels below the faggots is
stronger than that which was pumped up. After thus getting rid of
a large part of the water, the remaining portion is driven off by
boiling. The success of this process depends on the condition of
the atmosphere with respect to moisture. If the air, at the time
the brine falls through the faggots, holds in solution as much
moisture as it can contain in an invisible state, no more can be
absorbed from the salt water, and the labour expended in pumping
is entirely wasted. The state of the air, as to dryness, is
therefore an important consideration in fixing the time when this
operation is to be performed; and an attentive examination of its
state, by means of the hygrometer, might be productive of some
economy of labour.
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