Epworth, Joan, and Billy soon grew weary of life with the Selinites. They were banqueted, honored in every way possible, and assured constantly of the gratitude and friendship of Moawha and her people. But the people were little, the houses were small, life was narrowed to investigations of the interior of the moon, and what they could learn from the Selinite scientists.

In addition to this Epworth felt that it was his duty to go back to the Aerolite, and give aid to the colonists. They had made him co-leader with Toplinsky; and they expected him to give them the best advice and help he could. It entered his mind that he could bring them down into the interior of the moon where they could live with greater ease.

But when he spoke of this to Moawha she demurred. She had heard about the colonists from Joan, and she was not impressed with the idea of turning a lot of robbers and bad men loose among her people.

“At first, under your control, they might behave themselves,” she said, “but if you were to die they might decide to run wild, and annoy my people.”

“That is true,” Epworth admitted reluctantly. “I am not bragging about their religious background.”

“Even if I agreed, there comes the question of getting them here. How would you manage that? How will you go back to them?”

“We might take them back to the earth,” Billy suggested.

“That is another problem with Toplinsky dead. Just the same I am going to see just how easy it will be for us to fly up to the outer crust through Crater Agrippa.”

“When you make the attempt I go with you,” said the loyal Joan.

“Count me in it,” Billy added.

“Very well; we are on our way.”

To accomplish the ascending flight Epworth made three large motor-gliders. Well supplied with provisions for the trip, the three hardy Americans, accompanied by Moawha, made their way to the spot where the hole of the crater opened out from the inner world of the moon. It was a great frowning, black hole but the hardy adventurers did not let the looks of the route affect them. They bade Moawha a pleasant farewell, climbed into their gliders, and began to pedal around in a circle. In this manner they soon left the land of the Selinites, the light of day, and climbed up into the darkness with their flashlights in hand and their cavern lanterns fastened to their heads.

The upward trip was uneventful until Epworth suddenly found himself flying near a roof of large boulders and rocks which had not been there when they came down from the cricket nest. When he was joined by Joan and Billy all three flew around in a circle looking for an opening that would lead them upward.

They could find no way to go out.

“What has happened?” Billy inquired in great alarm when they discovered that their way out was blocked. “All these rocks were not here when we came down.”

“It looks to me as if that terrific explosion that Toplinsky set off has caused the insides of the crater to fall in and block all passage upward,” Epworth reasoned. “We are probably in a part of the crater which was narrow, and when the big boulders fell they crashed together.”

“That means that we are not going out,” Joan observed very quietly. She was very anxious to get out and try to get back to the earth. Of the three she was the one who had little interest in the inside of the moon. “I—I—had been building up great hopes.”

Epworth made a thorough examination of the rocks and debris that blocked the way.

“We are not going out this way,” he said, shaking his head sadly. “It looks as if we are doomed to become Selinites.”

“Moawha and her people are very charming,” Joan added thoughtfully, “but they are not our kind of people. They like us now but the Selinites may take a notion to change rulers over night. If they did we might not be so popular.”

“The light in the Land of the Selinites is steady, constant, and never lets up,” Billy put in. “You have explained that to me with the statement that the sun shines all the time through an open space in Mount Leibnitz. That means that there is an outer opening in that mountain. Why not try going out that way?”

“Billy, you are a scholar and a statesman,” Epworth declared enthusiastically. “We will do that very thing.”

They returned to Moawha’s city, and explained to her why they could not go on to the outer portion of the moon. When they told her that they were going to try to go out through the hole in Mount Leibnitz she immediately informed them that she would go with them as far as Mount Leibnitz.

Moawha had spent her entire life in the Land of the Selinites, and the idea that there was a great ball of fire out in space and shining through the outer rim of the moon was new and strange to her.

“I can’t believe that there is such a fire,” she exclaimed. “If there is I want to see it.”

Again Epworth, Joan and Billy, accompanied by Moawha, made a journey with a view of gaining the exterior. It was not a hard trip. All four had motor-gliders, and were able to fly easily over the rugged hills and interior projections of the moon which stuck up like small mountains.

But as they approached the great Mount Leibnitz the air grew warmer and warmer. Presently it became intensely hot, and even when they faced this heat they did not get a view of the sun. It was the steady flame of sunlight reflected against the rugged interior near the south pole that created the heat.

Nevertheless Epworth insisted on pressing onward. Finally they came to a mountain that ran up into a sharp peak. This mountain reflected many and varied coruscations, indicating that it was a large heap of colored stones. The heat here was almost unbearable but Epworth persisted in his advance until the three stood on a high peak with a blazing light all around them. Epworth was the first one to climb to the top of this peak.

“There, Moawha, is the mass of fire that makes the light and heat for your world.”

He turned, and lifted the little queen in his arms. What she saw caused her to cover her eyes with her hands and scream.

A great ball of blazing fire, bigger than anything Epworth had ever seen, shot down at them from out of the sky. Its heat was scorching, burning, blistering. Just a few moments under that blazing glare, and their clothing would be scorched, their flesh would be a mass of blisters, and they would fall down never to rise, yet this was their only way out!

“We can’t go out here,” Joan remarked quietly, as she pulled her brother back so that he was protected from the blazing sun by the top of the mountain. “This is just the beginning. There may be miles and miles of heated interior before we can get out of the hole to outer space.”

“Then we will have the same heat until we get to a point where the movements of the moon bring about the fourteen days of night.” Billy’s voice was mournful. “It looks to me that we are inside of the moon for keeps.”

Epworth led them down the mountain side to a spot where they were given the shadows of the hill in a way that brought a little relief from the terrible blaze. When he stopped he glanced at Joan’s hat. It was a combination of light straw and cloth, held away from her head by four slender slits of leather in such a way that the air percolated through her hair.

Taking the hat in his hand he studied it for several moments.

“I have an idea,” he said quietly. “Let’s go back to the Land of the Selinites, and work it out.”

Blindly his companions followed him, and for two weeks Epworth worked with the best scientists of the Land.

The result of this labor was the construction of three hollow body-helmets of asbestos, held away from the skin of the body so that air could percolate between the asbestos and their bodies. Air helmets for their heads were also made of asbestos. In addition to this, they covered their gliders with asbestos. Over all Epworth spread a coat of aluminum.

Thus prepared they flew again to the South Pole. Moawha went with them.

“I am not going to let my good friends leave me as long as I can see them,” she assured them. “Maybe you will have to come back again. I hope so. But if you do not you shall know that Moawha loves you, and wants you with her.”

It was a solemn parting. They left Moawha standing on the shady side of Mount Leibnitz’ peak waving her hand at them, and crying softly.

All three sprang into the air at the same time. Epworth jockeyed his glider near to Joan, and pointed upward. Upward meant straight into a blazing sun without any signs of land around them until they passed out of the crater.

“That for the heat!” shouted Billy when he got up into the glare of the sun, and discovered that the improvised protection would in a way answer the purpose. “I can stand a little heat.”

But he had no idea of the heat he would have to stand. Soon he discovered that he had spoken joyfully too soon.

It was an endless fiery furnace. Hour after hour they circled upward and outward. The hole in Mount Leibnitz proved of enormous size; the heat was greater than any they had ever encountered.

Fortunately Epworth had brought his binoculars with him, and using these, and his natural orientation, he was able to keep near the western line of the crater and know when they had left the inner part of the moon and had gained the outer portion.

Then began another long, wearisome journey, traveling over the surface of the moon without a compass. Putting the sun to their backs the three flew on, and on and on. But to give all the details of that terrible trip through blinding, blazing heat would necessitate a volume. They found some diminution in the heat after leaving the crater of Mount Leibnitz. Had it not been so they would never have accomplished their journey.

But finally they got to the Sea of Vapours and the lake that Toplinsky had made. Here they met with a pleasant surprise.

Epworth and Billy were of the opinion that they would experience much trouble in learning to operate the Aerolite. The nearer they got to the Rocket ship the more depressed they became because of this idea.

But when they landed near the Aerolite they were met by Michael Strauss. He greeted them joyfully.

“You are just in time,” he said, shaking their hands heartily. “I have been digging into Toplinsky’s desk. The giant left hidden there some blue prints of the Aerolite, and instructions about controlling it, and directing its course. These instructions are simple to a navigator and mechanic, and now that Toplinsky is dead I will undertake to guide the Rocket back to the earth.”

Gladly Epworth placed the matter in Michael’s hands after he had read the instructions, and under Michael’s skillful navigation the trip was made safely.

Naturally Toplinsky’s moon colonization scheme fell through but Epworth gave the colonists time to disappear from the Arctic camp, and then he and Joan and Billy found their way back to America, and sent government planes to recover the loot Toplinsky had stolen.

But one mystery always remained to trouble the astronomers. What had made the dark spot near the corner of the Sea of Vapours, and why did it gradually vanish?