It is
not until he has been thus a dozen times deceived, that he is willing to
relinquish the pursuit, and then, perhaps, when he really does see a
pond, he will pass it unexamined, from fear of another disappointment.
The philosophy of these false ponds I have never seen satisfactorily
explained. They have usually been attributed to a refraction, by which a
section of the bordering sky is thrown below the horizon; but I am
convinced that they are the effect of reflection. It seems that a gas
(emanating probably from the heated earth and its vegetable matter)
floats upon the elevated flats, and is of sufficient density, when
viewed obliquely, to reflect the objects beyond it; thus the opposing
sky being reflected in the pond of gas, gives the appearance of water.
As a proof that it is the effect of reflection, I have often observed
the distant knolls and trees which were situated near the horizon beyond
the mirage, distinctly inverted in the "pond." Now, were the mirage the
result of refraction, these would appear on it erect, only cast below
the surface. Many are the singular atmospheric phenomena observable upon
the plains, and they would afford a field of interesting researches for
the curious natural philosopher.
We had a pleasant journey, although sometimes pressed pretty hard by
hunger.
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