Naida and all the others were silent. The conflict between their reverence for the food and their clear desire to eat it, now that it was become the food of their leader, was pathetic.

Kirby put one of the strips in Naida's hand.

"Why not?" he asked. "We have bested the Duca in fair fight. We have seized his tower. Why not eat his food?"

As he had hoped it would, the suggestion at last settled the matter. A moment later, as Naida nibbled her first bite, she smiled.

"Why, it--it's good!"

With the question of provisions settled at least for a time, Kirby's next thought was of the tower. The present lull of peace seemed made for exploration.

"Come along," he said to Naida, "we've plenty to do," and then, when he explained, they set out, accompanied by Nini, a cousin of Naida's, and Ivana, a younger sister.

All of the others remained with little Elana.

While they climbed spiral stairs, Naida explained that the chamber they had just left was used by the Duca as a place in which he prayed before and after contacts with caciques or subjects. A sort of halfway station between earth and heaven, as it were, where the Duca might be purged of any sullying influence gained from human relationships.

At thought of the rank, egotistical hypocrisy implied by the story, Kirby smiled grimly. Then they came to a new door, heavier than that which barricaded the prayer chamber. Unlocked, the thing swung ponderously at Kirby's push, and with the three girls pressing close beside him, he entered--and stopped.

"Naida!" he gasped.

"Oh, _oh_!" she cried, and while Nini and Ivana gasped, she clapped her hands in an instinctive, feminine reaction of joy. "But there are things here which I believe none but the Ducas of our race have ever seen! Oh!

Why, the sacred girdle is as nothing compared to this display!"

By "display" she meant a treasure which took Kirby's breath away, which made his heart act queerly.

The walls of the chamber were fashioned of polished blocks of obsidion on which stood out in heavy bas-relief a maze of decorative figures fashioned of pure, beaten gold--the same kind of gold which had gone into the making of the cylinder of gold. With his first glance at the gorgeously wrought motifs of Feathered Serpent and Sun and Moon symbols, Kirby knew to a certainty whence the golden cylinder had come originally.

But even the gold--literally tons of it there must have been--was nothing compared to the gems.

They were spread out in blinding array upon a great table in the center of the room. There were pearls as big as turkey eggs and whiter, softer than the light of a June morning growing in the East. There were rubies.

One amongst the many was the size of a baseball and glowed like the heart of a red star. The least of the two or three hundred gems would have outcla.s.sed the greatest treasures of the Crown jewels of England and Russia combined.

Most overwhelming of all, however, was the jewel which rested against a square of black cloth all its own in the center of the table. While his heart still acted queerly, while Naida, Nini, and Ivana hung back, delighted, but still too bewildered to move, Kirby advanced and took gingerly in his hands a single white diamond about eighteen inches long, and almost as wide and deep as it was long.

The thing was carved with exquisite cunning to a likeness of the living head of Quetzalcoatl, the Feathered Serpent.

Kirby dared not guess how many pounds the carven hunk of flashing, blue-white carbon weighed. He knew only that like it there was no other diamond in the world, and that the thing was real. Naida and the two girls were silent now, and suddenly Kirby realized that to their awe of the gem was added awe of deepest religious nature. Slowly he put the diamond head of the Serpent back upon its square of cloth.

"We--we had heard that this thing existed," Naida said presently, voice hushed, "but no one except the holy men of our race has ever beheld it."

"But, what is it?" Kirby asked. "Whence came it?"

However, when Naida would have answered, he interrupted.

"But wait! Tell me as we go. We could stay here for the rest of our lives without much trouble, but we've got to cover the rest of the tower and get back to the others."

It was after they had closed the door to the treasure room that Naida told him the story.

"There is not so much to tell," she began. "The diamond itself is so gorgeous that it is hard to talk about. But here is the story. A great many ages ago one of the Ducas of our race found the diamond, decided to carve it into a perfect likeness of the head of the Serpent G.o.d. All of the craftsmen of the race helped him and when they were done, they took their image to Quetzalcoatl himself, and showed him what they had done.

"Quetzalcoatl was pleased. So pleased, that he promised all of the wise men that he would cease to prey upon them as he had in the past, and henceforward would take his toll of sacrifice from the ape-men alone.

Them he hated and would continue to hate because they worshipped not him but Xlotli.

"And so it came about," Naida went on slowly, looking up at Kirby as they still mounted wide steps to the upper reaches of the tower, "that our people gained immunity from a G.o.d which had always before harmed and destroyed them. Our race presently began to build this castle here on the high plateau, and Quetzalcoatl kept his compact with them. He still comes out of his chasm at intervals and preys upon the ape-men, but no one of our race has seen him for thousands of years, and he has always let us alone. And there is the whole myth and explanation of why the great diamond is revered among us as a holy of holies."

They had mounted to a new door which Kirby guessed might give entrance to the Duca's living quarters. But he was in no mood to open it at once.

"Wait a minute," he said as they all paused. "You say that, although none of your race has seen Quetzalcoatl since the diamond head was carved, he still comes out of his chasm and makes trouble for the ape-men. Just what does that mean?"

"Why--" Naida looked at him wonderingly. "I mean what I have said. The Serpent comes out of his chasm and--"

"What chasm?" Kirby asked sharply.

"Why, the one we crossed this morning. It extends to the far reaches of our country, beyond the Rorroh forest, where the ape-men dwell but which our people never visit. It is in that distant part of the chasm that the Serpent dwells."

"But--but--Oh, good Lord!" Kirby whistled softly. "Naida, do you mean to tell me that Quetzalcoatl was not simply a mythical monster, but an actual, living serpent which is alive _now_?"

Naida and the others shrugged.

"Why not?" she answered. "Sometimes we have captured a few ape-men, and they tell us stories of how Quetzalcoatl kills them. _They_ say he is very much alive."

"But," Kirby mumbled in increasing wonder, "is this living creature the same which your ancestors worshipped first as long ago, perhaps, as a million years?"

"That," Naida answered unhesitatingly, "I'm not sure of. Our caciques believe that the Serpent, although it lives longer than any other sentient thing, finally dies and is succeeded by a new Serpent which is reproduced by itself, within its own body."

So overwhelming did Kirby find this unexpected sequel to their discovery of the great diamond head, so staggered was he by the fact that Quetzalcoatl, of Aztecan myth, might exist as a sentient creature here in this cavern world, that he had little heart left for exploring other wonders.

Nevertheless, he presently pushed open the new door before which they had paused, and behind it found, as he had expected, the Duca's living quarters.

These were as severe as the jewel chamber had been gorgeous. A thin pallet spread upon a frame of wood formed the bed, and beside it stood a single stiff chair. That was all. The walls of glistening obsidion were bare.

There was, however, a door in one circular wall, and as Kirby flung this open, his previous disappointment changed to delight. For shelves along the walls of the small chamber held roll after roll of parchment covered with script. And in one corner lay six undamaged, almost new Mannlichers and several hundred rounds of ammunition!

"Naida," he exclaimed, "do you know what those are?"

"I suppose that they are weapons of the sort you used against the ape-men this morning?"