enemy was approaching, and after peering just over
the edge, he descended, and they went on down the defile as fast as
their horses could walk.

CHAPTER TWENTY THREE.

THE PROFESSOR IS STARTLED.

It was an exciting flight, the more so from the fact that they were
obliged to keep on at a foot-pace because of the baggage-horses, when at
any moment they knew that the enemy might appear behind in full chase.
Certainly the road was bad, and it was only here and there that they
could have ventured upon a trot or canter; but this did not lessen the
anxiety that was felt.

A dozen times over the professor would have been glad to pause and
investigate some wonderful chasm or rift, but Yussuf was inexorable. He
pointed out that it would be madness to stop, for at any time the enemy
might appear in sight, so Mr Preston had to resign himself to his fate.

It was the same when, during the heat of the afternoon, they came to the
ruins of a tower placed upon an angle in the defile quite a thousand
feet above the rough track, so as to command a good view in every
direction. From where they stood it looked ancient enough to have been
erected far back in the days when the armies of Assyria or Egypt passed
through these gates of the country; certainly it was not later than the
Roman times.

"One might find inscriptions, perhaps, or something else to explain when
it was made," said the professor. "Come, Yussuf, don't you think we
might stop and ascend here?"

"No, effendi," replied Yussuf sternly. "Those dogs may be close upon
our track, and I cannot let you run risks. We are not all men."

"Yussuf is perfectly right," said Mr Burne, who had become quite
reconciled to his fez with its gaudy roll of yellow silk; in fact, two
or three times over he had taken it off and held it up to examine it as
it rested on his fist. "He is perfectly right," he repeated, "we do not
want to fight, unless driven to extremities, and discretion is the
better part of valour."

"Yes," said the professor, looking up longingly at the watch-tower,
"but--"

"Now, my dear Preston, you really must not run risks for the sake of a
few stones," cried the old lawyer. "Come."

There was no help for it, so the professor sighed, and they rode slowly
on, with the heat growing more and more intense, till toward sundown,
when, about a hundred and fifty feet above the path, there was a cluster
of ruins, evidently of quite modern date, and among them a f