" said Griggs; "then the sooner we're off the better."

Wilton sighed as they mounted, and gave a last glance at the beauties of
the gully in which they had encamped, and again soon after as the little
train wound on, with Skeeter's bell chiming to the motion of his head,
for at a turn before descending to the lower ground he had a glimpse of
the far-spreading desert they were about to attack. It was beautiful in
its way, but the grey monotony soon palled upon him who looked, and the
eyes eagerly turned again to the refreshing green.

In a couple of hours the last shrub had been left behind, and every one
drew his breath hard and set his teeth, in the determination not to be
baffled by the lesser troubles likely to hinder their way; but all the
same, sighs once more rose for the beauty of the scenes and the
refreshing breath of the mountains, which was already rapidly giving
place to the hot reek of the sand and salt.

For a time the boys were startled into wonderment at the change which
came over the scene as the sun rose higher, for as the hazy mist that
overspread the plain began to rise, there before them lay spread-out a
wonderful expanse of water, one huge lake extending right to the
horizon, dotted here and there with islands of beautiful form.

"Why, I didn't know--" began Chris.

"Nor I," cried Ned. "We shan't want for water."

They pressed on to join the doctor and Griggs, who were once more
leading, and before either of the boys could open his lips to question,
the former exclaimed--

"There, boys, you never saw the mirage so beautiful as that."

"Mirage! Then it isn't water?"

"Water? No; only a peculiar effect seen in the atmosphere over a heated
plain. We shall see no water till we near the mountains on the other
side. But there, talk as little as you can, and avoid this heated dust
which rises from the mules' hoofs."

"It's wonderful!" cried Ned thoughtfully. "I felt sure that we were
near a beautiful lake."

"Such as deceives travellers sometimes."

"Ah, it's bad," said Griggs, "when you're crossing a plain, choking with
thirst, and the water-bottles are empty. A sight like that has driven
men mad before now with disappointment."

The boys recalled these words over and over again during their journey,
for from the very first they realised what a tramp through such a desert
meant--the sun came down with scorching power, and it was reflected up
from the white sand and salt. At mid-d