The Professor turned towards them and shook his head.

"Can't you see?" he pointed out. "It's a mirage--a desert mirage. They are
quite common at dusk."

Lenora for a moment was hysterical, and even Laura gave a little sob.
Quest set his teeth and glanced at the Professor.

[Illustration: "WHILE WE ARE WAITING, LET'S GO IN AND BE SHOCKED!"]

[Illustration: "YOU MUST THANK HIM FOR YOUR LIVES--THE MONGARS NEVER TAKE
PRISONERS."]

"Always water near where there's a mirage, isn't there, Professor?"

"That's so," the Professor agreed. "We are coming to something, all
right."

They struggled on once more. Night came and brought with it a half
soothing, half torturing coolness. That vain straining of the eyes upon
the horizon, at any rate, was spared to them. They slept in a fashion, but
soon after dawn they were on their feet again. They were silent now, for
their tongues were swollen and talk had become painful. Their walk had
become a shamble, but there was one expression in their haggard faces
common to all of them--the brave, dogged desire to struggle on to the
last. Suddenly Quest, who had gone a little out of his way to mount a low
ridge of sand-hills, waved his arm furiously. He was holding his
field-glasses to his eyes. It was wonderful how that ray of hope
transformed them. They hurried to where he was. He passed the glasses to