And only after an interval
that seemed unconscionably long to me the whole pool
settled back to comparative smoothness, though without
its definite plane of demarcation now. Strange to say,
the dog had actually started something, a rabbit maybe
or a jumping deer, and did not return.
When fogs spread, as a rule they do so in air already
saturated with moisture. What really spreads, is the cold
air which by mixing with, and thereby cooling, the warmer,
moisture-laden atmosphere causes the condensation. That
is why our fall mists mostly are formed in an exceedingly
slight but still noticeable breeze. But in the case of
these northern mist pools, whenever the conditions are
favourable for their formation, the moisture of the upper
air seems to be pretty well condensed as dew It is only
in the hollows of the ground that it remains suspended
in this curious way. I cannot, so far, say whether it is
due to the fact that where radiation is largely thrown
back upon the walls of the hollow, the fall in temperature
at first is very much slower than in the open, thus
enabling the moisture to remain in suspension; or whether
the hollows serve as collecting reservoirs for the cold
air from the surrounding territory--the air carrying the
already condensed moisture with it; or whether, lastly,
it is simply due to a greater saturation of the atmosphere
in these cavities, consequent upon the greater approach
of their bottom to the level of the ground water.
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