the waters of
which rippled brightly in the sunshine, and upon its banks long lines of
infantry were drawn up, or what appeared to be infantry, all standing
silent and motionless as so many statues.

The two boys gazed in the utmost bewilderment at this spectacle, while
Lion bounded forward, evidently meditating a plunge into the cool and
sparkling waters. The astonishment of the party was in no way
diminished, when the doctor, raising his gun to his shoulder, fired
directly at the nearest platoon of soldiers, one of whom was seen to
fall. The next moment the whole of his companions rose with loud
screams into the air, and dispersed themselves in all directions.
Almost at the same moment the walls and battlements of the fortress and
ridges of roof behind them wavered and shook, and finally vanished from
the scene, as the smoke of a wood fire is lost in the surrounding
atmosphere. In their place appeared a low serrated ridge of rock, on
which a few stunted shrubs were growing, while in front and behind alike
extended the interminable waste of sand.

"Here is your soldier, Nick," said the doctor, as he picked up the
carcass of a large flamingo, which his shot had brought down. "Here's
his red cap and jacket--his beak and wings, that is to say--and here are
his white facings--his neck and chest. You are not the first by a good
many that has made that mistake!"

"This is what is called a mirage, then?" said Frank. "I've often heard
of it, and longed to see it; and it is a more extraordinary delusion
than I could have supposed possible. Why that low line of rock there,
and those dwarf shrubs looked as if they were at least sixty feet high.
How in the world do you account for it, Mr Lavie? Why even Lion was
taken in!"

"I am afraid I cannot give you an explanation, which you will understand
very clearly, Frank. It is caused by the inequality of the temperature
in the lower strata of the air; which again is the result of the
reflected heat of the sun's rays on the barren, sandy plain. While the
strata are unequally heated, these curious reflections, which are like
those seen in broken mirrors, continue to deceive the eye. Objects
appear to be raised high into the air, which in reality are to be found
on the surface of the earth, often too they are immensely magnified, as
indeed you saw just now; a single stone will seem the size of a house,
and an insignificant shrub look as big as a forest tree. But when the