“On the far side,” said the dragoman, waving his donkey-whip towards the east, “is the military line which conducts Wady Halfa to Sarras.  Sarras lies to the south, under that black hill.  Those two blue mountains which you see very far away are in Dongola, more than a hundred miles from Sarras.  The railway there is forty miles long, and has been much annoyed by the Dervishes, who are very glad to turn the rails into spears.  The telegraph wires are also much appreciated thereby.  Now, if you will kindly turn round, I will explain, also, what we see upon the other side.”

It was a view which, when once seen, must always haunt the mind.  Such an expanse of savage and unrelieved desert might be part of some cold and burned-out planet rather than of this fertile and bountiful earth.  Away and away it stretched to die into a soft, violet haze in the extremest distance.  In the foreground the sand was of a bright golden yellow, which was quite dazzling in the sunshine.  Here and there, in a scattered cordon, stood the six trusty negro soldiers leaning motionless upon their rifles, and each throwing a shadow which looked as solid as himself.  But beyond this golden plain lay a low line of those black slag-heaps, with yellow sand-valleys winding between them.  These in their turn were topped by higher and more fantastic hills, and these by others, peeping over each other’s shoulders until they blended with that distant violet haze.  None of these hills were of any height—­a few hundred feet at the most—­but their savage, saw-toothed crests, and their steep scarps of sun-baked stone, gave them a fierce character of their own.

“The Libyan Desert,” said the dragoman, with a proud wave of his hand.  “The greatest desert in the world.  Suppose you travel right west from here, and turn neither to the north nor to the south, the first houses you would come to would be in America.  That make you home-sick, Miss Adams, I believe?”

But the American old maid had her attention drawn away by the conduct of Sadie, who had caught her arm by one hand and was pointing over the desert with the other.

“Well, now, if that isn’t too picturesque for anything!” she cried, with a flush of excitement upon her pretty face.  “Do look, Mr. Stephens!  That’s just the one only thing we wanted to make it just perfectly grand.  See the men upon the camels coming out from between those hills!”

They all looked at the long string of red-turbaned riders who were winding out of the ravine, and there fell such a hush that the buzzing of the flies sounded quite loud upon their ears.  Colonel Cochrane had lit a match, and he stood with it in one hand and the unlit cigarette in the other until the flame licked round his fingers.  Belmont whistled.  The dragoman stood staring with his mouth half-open, and a curious slaty tint in his full, red lips.  The others looked from one to the other with an uneasy sense that there was something wrong.  It was the Colonel who broke the silence.