d.

Raal studied the horizon carefully with narrowed eyes. "No, Master.
When the sandstorm comes from the desert, it is not like that.
Overhead the color changes and threatens danger. It may be a herd of
wild horses that raises the dust."

"Do wild horses run about on the desert?" asked Dan.

"Never before have I seen them, but of late I have seen many strange
things. I have seen birds that carry men and I have seen the sun
darkened."

Dick took his binoculars and studied the morning cloud, but it was too
far for him to make out what was kicking up the dust. Dan looked
without success, and Dick turned to the natives.

"You try what you can see," he said to Raal, handing over the
binoculars.

The Taharan took the "magic glasses" with awe. Never could he outgrow
the superstitious terror that they aroused.

"They won't hurt you," laughed Dan. "Take a chance! You saw me use
them."

"Yet they are strong magic. I fear them because I do not understand."

"It's all right. They are harmless to you. Look!" And as Dick helped
him to focus the binoculars, Raal cried out in amazement.

"Ah-woe, ah-woe! I see warriors!--Or demons, mounted on horses! The
magic brings them close! Ah-woe!"

Dick took the glasses and thought he could make out what the sharp-eyed
savage had seen.

"Arabs!" he gasped. "A wild tribe of nomads!"

"Arabs, Master?"

Raal did not know what he was talking about. Never had raiding Arabs
found this spot so far from the caravan trails. In the history of the
tribe, no strangers had ever visited the land until the airplanes had
brought Dick and those others from the sky. Yet with the instinct of
the savage, Raal was quick to grasp the idea of a raid by enemies.

"Arabs! If they be men, we will fight them!"

"Lucky for you we are here to protect you!" said Dan.

"Quick, Raal!" cried Dick. "Assemble the warriors with all their
weapons. Spears, bows and arrows, stone hatchets and knives! Order
the war drums to be sounded!"

"I hear, O Master!"

Raal hurried to obey. Shaggy blond tribesmen sprang to the hollow
logs, with tightly stretched hides and soon the roll of the drums
brought Taharan warriors hurrying from the fields. The alarm throbbed
until the air was vibrating with a feeling of menace. The call to
battle carried over the cliffs and beyond to the Gorol tree dwellings,
and soon the ape-men were seen, scrambling down the steep rocks, with
their war chief, Kulki,