It is very rare,
indeed, that they reach those mountains, and not till the afternoon is
considerably advanced. A light northwesterly breeze is, for the most
part, felt there, while an easterly or northeasterly wind is blowing
strongly in the lower country. How far northward and southward of
Virginia, this easterly breeze Takes place, I am not informed. I must,
therefore, be understood as speaking of that State only, which extends
on the sea coast from 36 1/2 to 38 deg. of latitude.
This is the fact. We know too little of the operations of nature in the
physical world, to assign causes with any degree of confidence. Willing
always, however, to guess at what we do not know, I have sometimes
indulged myself with conjectures on the causes of the phenomena above
stated. I will hazard them on paper, for your amusement, premising for
their foundation some principles believed to be true.
Air resting on a heated and reflecting surface, becomes warmer, rarer,
and lighter: it ascends therefore, and the circumjacent air, which is
colder and heavier, flows into its place, becomes warmed and lightened
in its turn, ascends, and is succeeded as that which went before.
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