The Master’s only answer was to draw from his pocket an extra lethal gun, hand it over and, in a whisper, hastily instruct the Frenchman how to use it.  Then he cried, loudly: 

“Ready, men!  Fire!”

All along the line, the faint, sighing hiss of the strange weapons sounded.  Over the top of the dune little, almost inaudible explosions began taking place as—­plop! plop! plop!—­the capsules burst.  Not now could their pale virescence be seen; but the Master smiled again, at realization that already the lethal gas was settling down upon the horde of Shiah outcasts.

To Leclair he whispered in Arabic an ancient saying of the desert folk:  “’Allah hath given skill to three things, the hands of the Chinese, the brains of the Franks, the tongues of the Arabs!’” He added:  “When the gas strikes them, they would think the Frankish brain more wonderful than ever—­if they could think at all!”

He slid his hand into the breast of his jacket, pulled a little cord and drew out a silver whistle, the very same that he had used at Gallipoli.  As he slid it to his lips, they tautened.  A flood of memories surged over him.  His fighting-blood was up, like that of all the other Legionaries in that hasty trench-line along the white sand-drifts.

A moment’s silence followed.  Outwardly, all was peace.  No sound but the waves broke the African stillness.  A little sand-grouse, known as kata by the Arabs, came whirring by.  Far aloft, a falcon wheeled, keen-eyed for prey.  Once more the deadly scorpion peeped from the skull, an ugly, sullen, envenomed thing.

The Master held up the silver whistle, glinting in the last sun-glow.  They saw it, and understood.  All hearts thrilled, tightening with the familiar sense of discipline.  Fists gripped revolver-butts; feet shuffled into the sand, getting a hold for the quick, forward leap.

Keenly trilled the whistle.  A shout broke from some twenty-five throats.  The men leaped up, forward, slipping, staggering in the fine sand, among the bunches of dried grass.  But forward they drove, and broke into a ragged, sliding charge up the breast of the dunes.

“Hold your fire, men!  Hold it—­then give ’em Hell!” the Master shouted.  He was in the first wave of the assault.  Close by came Rrisa, his brown face contracted with fanatic hate of the Beni Harb, despoilers of the Haram sanctuary.

There, too, was “Captain Alden,” grim with masked face.  There was Bohannan, Leclair—­and pistol-barrels flickered in the evening glow, and half the men gripped knives in their left hands, as well.  For this was to be a killing without quarter, to the very end.

CHAPTER XXIII

A MISSION OF DREAD

Panting, with a slither of dry sand under their laboring feet, the Legionaries charged.  At any second, a raking volley might burst from the dunes.  The lethal pellets—­so few in this vast space—­might not have taken effect.  Not one heart there but was steeling itself against ambush and a shriveling fire.