They stood on a shelf. Above, to each side, and below, stretched a sheer wall of rock. It looked almost vertical.

But a close inspection showed a procession of steps leading downward. Only from close range could these be discovered. They offered a way to safety, precarious though it might be.

Doc addressed his companions:

"Monk, you go back inside and start work on that sulphur deposit. Get it out as rapidly as you can. Select the purest stuff." He told Monk where he had noticed the sulphur.

"Johnny, you harvest a supply of the saltpeter. Was there much of it?"

"Quite a little," Johnny admitted.

"Dig it out. I think it is pure enough for our purpose. Maybe we can refine it a little."

Doc turned to pretty Princess Monja. He hesitated, then said: "Monja, you've been a brick."

"What's that?" she asked. Evidently her supply of English slang was limited.

"A wonderful girl," Doc grinned. "Now, will you do something else. It'll save time."

She smiled. "I will do anything you say."

The unmistakable adoration in her voice escaped Doc's notice.

He directed: "Return to the Mayans gathered under the pyramid. Select the most powerful and active among the men, and send them here, along with Long Tom, Renny, and Ham."

"I understand," she nodded.

"One thing more — send along a number of those gold vases. Select those with thick walls, very heavy. Say about fifty of them. Tell Renny, Long Tom, and Ham I want to make bombs out of them. They will know which ones will serve best."

"Bombs of gold!" Monk gulped.

"The only thing handy," Doc pointed out. "And when the men reach you fellows, load them up with the saltpeter and sulphur."

Before departing, Johnny asked a question. "Know where we are?"

Doc smiled and pointed. There was another wall of rock opposite them a few hundred yards. A thousand feet or so below poured a rushing stream.

"We're in the chasm. The Valley of the Vanished is somewhere upstream. And it can't be very far."

"The entrance to the valley is through the chasm, isn't it?" Monk queried.

"It is. Unless you count the new entrance we've just found."

Johnny, impatient, said: "Come on, Princess. Come on, Monk. Let's get going!"

WHEN the three had left him, Doc made his way along the precarious steps to more level footing. He found a patch of jungle. Gathering the proper woods, he selected a spot for making his charcoal where the smoke not be noticed.

The charcoal oven he built of stone and mortar. Two rocks flinty enough to spark a fire could not be located. So, with a leather string from his mantle, and a curved stick, he made a fire bow. This twirled a stick until friction started a tiny glow. In a moment he had a fire.

The charcoal-manufacturing process was well under way when his friends appeared. They had about a hundred of the most manly Mayan men. And from the way they were laden with golden jars, they might have thought they would not have another chance at the fabulous wealth.

The making of the charcoal was tedious. Work on the saltpeter and sulphur called for a great deal of Doc's vast ingenuity and knowledge.

All that afternoon and through the night, they prepared and mixed.

"We won't rush it," Doc explained. "This time we want to settle this red-fingered warrior menace for once and all."

He was ominously silent a bit, then added. "And one in special — the man in the snake suit."

From time to time, runners dispatched back through the long reaches of the cavern of treasure to its termination beneath the Mayan pyramid reported the defenders holding out successfully.

"They have repulsed several attacks," one messenger brought notice. "One of the fire-spitting snakes the red-fingered men are using brought hurt to our ruler, King Chaac, though."

"Is he hurt bad?" Doc demanded.

"In the leg only. He cannot walk about. But otherwise, he is not in bad shape."

"Who has charge of the defense?" Doc wanted to know.

"Princess Monja."

Monk, who had overheard, grinned from ear to ear. "Now there is a girl!"

The bombs were rapidly pushed to completion. Obsidian, glasslike rock flakes were placed in the gold jars. A quantity of the powder was poured in to from a core. The gold, being pure and soft, permitted the jars to be pounded together at the top. The pounding was done carefully.

Fuses offered a problem. Doc solved that by selecting lengths of a tough tropical vine which had a soft core. Using long, hardwood twigs, he poked out the core, leaving a hollow tube. One of these he left extending down into the powder of each bomb.

Making use of his vast fund of knowledge, Doc concocted a slow-burning variety of the gunpowder. He filled the improvised fuses with this, after experiments to see what lengths were proper.

With the first silvery glow of dawn, Doc led the attacking party on the march.

Some of the Mayans were familiar with the trail into the Valley of the Vanished. It seemed these men had been outside a time or two to further friendly relations with surrounding natives, who, though not pure Mayans after the passage of these centuries, were of Mayan ancestry. Hence the friendship with the lost clan.

Through the treacherous entrance to the valley, the grim little cavalcade worked. There was no lookout posted at the chasm path — the first time that had happened in centuries, a Mayan muttered.

Since the lookouts were usually red-fingered warriors, Doc understood how the snake man had been able to come and go, unnoticed.

Without revealing themselves to the besieging warriors, they closed in. The Mayans understood how to light the bombs. They carried smoldering pieces of punklike wood.

At Doc's signal, an even dozen bombs rained upon the red-fingered killers.

Chapter 21. THE GOLDEN DEATH

Thunderous explosion of those twelve bombs was the first warning those of the warrior sect had of the attack.

Doc had apportioned three explosive missiles to each of the four emplaced machine guns. He had instructed his Mayan followers in the art of hurling grenades. Just how well was instantly evident.

All four rapid-fire guns went out of commission at once!

The devilish warriors, rent and torn by the obsidian shrapnel, were tossed high into the air. Many perished instantly, paying in a full measure for their murderous attack on the Mayan citizenry during the ceremonials.

But plenty remained to put up a fierce fight.

And some had the guns which had belonged to Doc and his friends!

With piercing howls, the Mayans fell upon the surviving rascals. They bombed them wherever four or five were together.

Monk had picked up two stout clubs en route. One in either hand, he laid about with terrific results.

Renny needed no more than his great iron fists. Long Tom, Ham, and Johnny stood off and pitched bombs wherever opportunity presented.

Doc, his golden eyes throwing glances seemingly everywhere at once, moved back and forth through the combat. Time after time, red-fingered fiends dropped before his skill and strength without even knowing what manner of blow had downed them.

The great stone likeness of Kukulcan atop the pyramid gave a sudden lurch to one side, uncovering the secret entrance to the mammoth treasure vault of ancient Maya.

Tribesmen poured out. Roaring for vengeance on the red-fingered ones, they flooded down the pyramid stairs. Some fell in their excitement. They bounded up unhurt. Rocks, sticks, anything handy, they seized for the fray.

A spike of steel poked furtively out of a clump of jungle shrubs. It was the snout of a machine gun. It snarled two shots, four — bronze hand closed on the warming barrel. A hand with the strength of alloy steel. It jerked. The gunman, a finger unluckily hung in the trigger guard, was hauled out of the tropical foliage.