to lag.
The heat was intense, the sand, catching the sun's rays dazzled the
eyes and made them burn.

But no matter how fast they rode, the oasis seemed as far away as ever.
The caravan was lost in the shimmering haze.

"Who would have believed that it was so far away?" grumbled Dan Carter.
At that moment he caught sight of Dick's face. It was pale and
troubled.

"What's the matter, old sport?" Dan asked anxiously. "Are you sick or
something? Better take a sip of that precious water in the bag."

"No, I'm all right," answered Dick quietly, "but I'm wondering how I'm
going to explain a mirage to these savages."

"A mirage!" exclaimed Dan with a catch in his voice. "So that's why we
seemed to be getting farther away from that green spot all the time.
But Dick, are you certain? I'd have sworn it was the real thing."

But even as they talked, Dan noticed the thinning haze ahead. It
seemed to be rising and soon disappeared into the sky.

"Say, Dick, when did you catch on?" asked Dan.

"About five minutes ago. How am I going to explain it to them? They
may never have seen one and may think that it is black magic. See, the
caravan has vanished, too."

"Tell them it's Cimbula out there," said Dan with a laugh. "They'll
believe that, all right."

While the boys were talking, the haze dissolved completely, leaving a
far stretch of sandy waste.

"Ah-woe Tahara!" moaned Raal touching Dick's arm. "Look ahead. The
spirit of evil has swallowed up the oasis. It is a warning, O Master.
I have seen it many times before."

Dick gave a sigh of relief. At least the mirage was not unknown to the
tribesmen.

"A warning, what do you mean, Raal?" asked Dick.

"Thus comes the oasis on the desert at times, leading men to
destruction. Warriors depart to take possession of the new land and
find themselves without food and drink. They ride around in circles in
order to find the green oasis. Then at last the demons gobble them up.
Did you not see the caravan disappear? It is a bad omen, so say my
people."

Some of the tribesmen shielded their faces against the evil eye while
others muttered anxiously. A few turned as if to flee back to their
own land but at a sharp command from Dick they followed grumbling.

Dick halted his riders and they ate a hasty lunch while shielding
themselves in the shadow of their horses.

Late that afternoon they came to the oasis in the desert. The men
threw themselves flat on the