Chapter XI

They sat in Professor Staunton's laboratory, a square chamber where Earthly equipment taken from the wreck of his space-ship was mingled with typically Lunarian furniture and equipment. The walls were light blue, of that polished composition resembling bakelite that was used for building in the Caverns. The walls were about ten feet high, and they ended in an ornamental cornice without any ceiling or roof at all. Overhead there was a glow of misty light, and far above the rocky top of the cavern.

"Why should we need roofs?" Diana said in reply to Larry's surprised comment. "Here in these Caverns there is neither rain nor snow nor wind, nor any change in temperature at all. The walls give privacy, and there is no need for anything else."

Ripon was bending over a table on which Staunton had spread a large map of the Moon. The cavern of Chotan was indicated by a red dot, and Larry saw that there were a dozen others scattered around within a radius of a few hundred miles.

"Our space-cruiser was wrecked near one of the entrances to this cavern when we landed here thirty years ago," Staunton said. "As you have guessed, it was the inability to land safely with rockets, in a practically airless atmosphere where helicopters were useless, that smashed us. As you did, we had fortunately put on space suits before trying to land. Our ship was too badly wrecked for any chance of return."

"But how have you succeeded in getting all these people to learn English?" Ripon asked.

"They knew that language before I came! But it is best that I give you a hasty outline of Lunarian history. The simple-minded but husky Insect-men were the aboriginal inhabitants of the Moon. Long æons ago, while most of the people of Earth were living crudely in caves and using chipped stones for tools and weapons, an isolated people developed a high civilization in what I have roughly identified as the region of the Himalayas. A series of great earthquakes destroyed their civilization, but a large number of them escaped and came to the Moon in some kind of a space-ship. Here they found, in those days, a small planetary body that had a thin but breathable air. They founded a civilization on the other side of the Moon where it is always sunny, and called it Gral-Thala. Those were pleasant days, if the old legends are to be believed, the Golden Age of Lunarian civilization."

For a moment Staunton paused. All those in the room, including the Lunarians who had been familiar with this tale since childhood, hung intently on his words. The broad face of Pyatt of Kagan was somber and moody as he sat bent forward with the scabbard of his sword resting across his armored knees.

"As the centuries passed, the atmosphere continued to thin," Staunton went on, "so the Ancients took care to preserve what was left. Gral-Thala is in the fertile part of the Moon, and lies in a vast valley completely surrounded by a lofty mountain range. By means of the superior engineering knowledge of the Ancients, they built a lofty wall or barrier along the crest of the range so that its top is miles above the level of the valley floor. They then sucked all the air within the Great Barrier. Gral-Thala itself thus lies in a great pool of air surrounded by the ranges and the barrier. On the rest of the Moon, as here, air only remains in deep crevices and caverns like this."

"But these caves were a great labor in themselves..." Ripon began.

* * * * *

"Originally these caverns were built as outposts of Gral-Thala, built here because of their nearness to valuable mineral deposits. People came out from the sunlit cities within the Great Barrier to put in a tour of duty in the caverns. Again life on the Moon had reached a pleasant equilibrium. And then came the great disaster! Some two centuries ago a group of several hundred outlaws fleeing from Earth came here in a big space-ship."

"The _Mercury_!" Larry exclaimed.

"Exactly. Those men and women who came from Earth were few in comparison to the population of the Moon, but they were cruel and ruthless and they had weapons of war. The peaceful Lunarians had at that time no weapons at all, for they had no need for them. Within a few months the invaders made themselves Lords of all Gral-Thala! That was when English, the language of the invaders, came to be spoken by everybody on the Moon as well as the softer tongue of the Lunarians themselves. A few of the hardier folk in Gral-Thala fled to these caverns as outlaws. The invaders made only half-hearted attempts to come after them, and with the passing of the years the location of these refuges has been forgotten by people living within the Great Barrier. That is why these places are now known as the Lost Caverns."

"And the invaders still rule?"

"Their descendants are still Lords of Gral-Thala. Cruel and ruthless they always were, decadent and dissolute they have now become as well, but they still rule the sunny valley that was the pride of the ancient Lunarians. They hold the power, and they are aided by a few groups among the people of Gral-Thala who have sacrificed their honor to fawn upon their masters. Our spies, who penetrate beyond the barrier, tell us that before long there will come a day when the people are ready for revolt--but the time is not yet."

"But surely!" said Pyatt of Kagan, his deep voice breaking in on the low monotone in which Staunton had spoken, "surely our visitors will return to Earth, now that interplanetary travel has become possible, and bring us the warriors and equipment to storm the high palaces of the tyrants of Gral-Thala!"

"I should think that the Confederation of Earth would send help, particularly since the original invaders were outlaws from that planet," Staunton said. "How about it, friend Ripon? How are conditions back on Earth at this time?"

Ripon straightened up and shook his shoulders. The glow in his eyes faded away, and the lines in his face deepened once more.

"The Lunarians can look for no help from Earth until one thing is accomplished," he said. "I have been letting scientific enthusiasm make me lose sight of our reason for coming here. How are conditions on Earth, you ask? I can tell you in a single sentence. Unless we of Earth very quickly get a new supply of radium salts suitable for use with the Riesling Method, in a few weeks we all perish!"

"I do not understand."

In a few hasty phrases Ripon sketched the development of the terrible plague that was so swiftly robbing Earth of its inhabitants. At the end Staunton leaned back in his chair.

"Such salts are available on the Moon in ample quantity," he said slowly, and something in the quality of his voice robbed the words of the reassurance they would otherwise have held, "but--they are all located well within the area of the Great Barrier. And the Lords of Gral-Thala would never let you have even a single milligram!"

"Then there's only one thing to be done!" Larry stood up and began to peel off his space suit. "If someone will show me the way, I'll go into Gral-Thala and bring out as much of the radiatron extract as I can carry."

"And I will go with you!" boomed Pyatt of Kagan. "By Gorton and Laila, mythical gods of the Moon, it will take more than a few of those cold-eyed tyrants to stop us!"