Already a few of the Anthropoids were beginning to scramble down the opposite wall of stone.

"Men!" cried Allan commandingly, "not one of those creatures must ever reach this terrace! Take good aim. Waste no single shot. Every bullet must do its work!"

Choosing six of the best marksmen, he stationed them along the parapet with rifles. The firing began at once.

Irregularly the shots barked from the line of sharpshooters; and the little stabs of smoke, drifting out across the river, blent in a thin blue haze. Every moment or two, one of the Horde would writhe, scream, fall--or hang there twitching, to the cliff, with terrible, wild yells.

Stern greeted the return of Frumuos with eagerness.

"Here!" he exclaimed, scattering the arrows among half a dozen men.

"Bind these fireb.a.l.l.s fast to the arrowheads!"

He dealt out cord. In a moment the task was done.

"Sivad!" he called a man by name. "You, the best bowman of all! Here quickly!"

Even as Sivad fitted the first arrow to the string, and Stern was about to apply the torch, a rattling crash from above caused all to cringe and leap aside.

Down, leaping, ricochetting, thundering, hurtled a great boulder, spurning the cliff-face with a tremendous uproar.

It struck the parapet like a thirteen-inch sh.e.l.l, smashed out two yards of wall, and vanished in the depths. And after it, sliding, rattling and bouncing down, followed a rain of pebbles, fragments and detritus.

"Those two above--they're attacking!" shouted Stern. "Quick--after them! _You, you, you!_"

He told off half a dozen men with rifles and revolvers.

"Quick, before they can hide! Look out for their darts! _Kill! Kill!_"

The detachment started up the path at a run, eager for the hunt.

Stern set the flaring torch to the first fireball. It burst into bright flame.

"Shoot, Sivad! Shoot!" he commanded. "Shoot high, shoot far. Plant your arrow there in the dry undergrowth where the wind whips the jungle! Shoot and fail not!"

The stout bowman drew his arrow to the head, back, back till the flame licked his left hand.

"Zing-g-g-g-g!"

The humming bowspring sang in harmony with the zooning arrow. A swift blue streak split the air, high above the river. In a quick trajectory it leaped.

It vanished in the wind-swept forest. Almost before it had disappeared, Sivad had s.n.a.t.c.hed another flaming arrow and had planted it farther down stream.

One by one, till all were gone, the marksman sowed the seed of conflagration. And all the while, from the rifles along the parapet, death went spitting at the forefront of invasion.

Another boulder fell from aloft, this time working havoc; for as one of the riflemen sprang to dodge, it struck a shoulder of limestone, bounded, and took him fair on the back.

His cry was smashed clean out; he and the stone, together, plumbed the depths.

But, as though to echo it, shots began to clatter up above. Then all at once they ceased; and a cheer floated away across the canyon.

"_They're_ done, those two up there, d.a.m.n them!" shouted Stern. "And look, men, look! The fire takes! _The woods begin to burn!_"

True! Already in three places, coils of greasy smoke were beginning to writhe upward, as the resinous, dry undergrowth blossomed into red bouquets of flame.

Now another fire burst out; then the two remaining ones. From six centers the conflagration was already swiftly spreading.

Smoke-clouds began to drift downwind; and from the forest depths arose not only harsh cries from the panic-stricken Horde, but also beast and bird-calls as the startled fauna sought to flee this new, red terror.

Shouts and cheers of triumph burst from the little band of defenders on the terrace as the sweeping wind, flailing the flame through the sun-dried underbrush, whirled it crackling aloft in a quick-leaping storm of fire.

But Stern was silent as he watched the fierce and sudden onset of the conflagration. Between narrowed lids, as though calculating a grave problem, he observed the crazed birds taking sudden flight, launching into air and whirling drunkenly hither and yon with harsh cries for their last brief bit of life.

He listened to the animal calls in the forest and to the strange crashings of the underwood as the creatures broke cover and in vain sought safety.

Mingled with these sounds were others--yells, shrieks, and gibberings--the tumult of the perishing Horde.

Swiftly the fire spread to right and left, even as it ate northward from the river.

The ma.s.s of Anthropoids inevitably found themselves trapped; their slouching, awkward figures could here or there be seen in some clear s.p.a.ce, running wildly. Then, with a gust of flame, that s.p.a.ce, too, vanished, and all was one red glare.

The riflemen, meanwhile, were steadily potting such of the little demons as still were crawling up or down the cliffside opposite.

Surely, relentlessly, they shot the invaders down. And, even as Stern watched, the enemy melted and vanished before his eyes.

Allan was thinking.

"What may this not result in?" he wondered as he observed the swift and angry leap of the forest-fire to northward. "It may ravage thousands of square miles before rain puts an end to it. It may devastate the whole country. A change in the wind may even drive it back on us, across the river, sweeping all before it. This may mean ruin!"

He paused a moment, then said aloud:

"Ruin, perhaps. Yes; but the alternative was death! There was no other way!"

Now none of the attackers remained save a few feebly twitching, writhing bodies caught on some protuberance of rock. Here, there, one of these fell, and like the rest was borne away down stream.

Through the heated air already verberated a strange roar as the forest-fire leaped up the opposite hillside in one clear lick of incandescence. This roar hummed through the heavens and trembled over the long reaches of the river.

The fire jumped a little valley and took the second hill, burning as clear as any furnace, with a swift onward, upward slant as the wind fanned it forward through the dry brush and among the crowded palms.

Now and then, with a m.u.f.fled explosion, a sap-filled palm burst. Here, or yonder, some brighter flare showed where the fire had run at one clear leap right to the fronded top of a fern-tree.

Fire-brands and dry-kye, caught up by the swirl, spiralled through the thick air and fell far in advance of the main fire-army, each outpost colonizing into swift destruction.

Already the nearer portion of the opposite cliff-edge was barren and smoking, swept clean of life as a broom might sweep an ant-hill.

Tourbillons of dense smoke obscured the sky.

The air flew thick with brands, live coals and flaring bits of bark, all whirling aloft on the breath of the fire-demon. Showers of burning jewels were sown broadcast by the resistless wind.

Stern, unspeakably saddened in spite of victory by this wholesale destruction of forest, fruit and game, turned away from the magnificent, the terrifying spectacle.

He left his riflemen staring at it, amazed and awed to silence by the splendor of the flame-tempest, which they watched through their eye-shields in absolute astonishment.