The tunnel passed several more large, open caverns where rich lodes of iron had been mined by the Agglemonians, and Shaun’s sword felt out several more wide shafts leading down to even deeper tunnels and passages.

     Half an hour after leaving the shallow pool, though, they came upon an airlock that was different from any they’d seen before. It was the same in its essentials, as they saw when Thomas took the glowbottle out again. It had the same large, circular wheel with a smaller wheel, an air pressure equalisation hole and a window. Unlike the Agglemonian airlocks, though, which were simple and plain in design, this one was covered with ornamental flourishes and decoration, turning it into a work of art. What was more, it was very similar to a form of art they’d seen before, in the abandoned trog village of Darmakarak.

     They stared in excitement. “I would venture to guess that this airlock was made by the moon trogs,” said Shaun.

     “They really exist then?” said Lirenna in delight.

     “So it seems,” replied the soldier.

     “Hey, there’s some kind of sign up there,” said Thomas, lifting up the glowbottle to see it better. It was metal, in which words had been engraved, but it was almost hidden beneath a layer of moss. He wiped it away and read what it said.

     “’You are at the edge of the Kronosian gravity sphere,’” he read. “’Beyond this point, gravity is only 1/500 that in Kronosia, growing less as you descend. Take care if you have little low gravity experience.’" He looked around at the others. "Looks like we’ve finally reached the official city limits,” he said.

     “Good,” replied Matthew. “Maybe the Konnens won’t pursue us any further.”

     “I wouldn’t count on it,” replied the wizard. “Lord Basil’ll want his ring back pretty badly. I doubt he’ll ever give up.”

     “Let’s not hang about then,” said Shaun. “Come on, let’s go.”

     There was gravity inside the airlock, but it stopped abruptly at the second door. Shaun stood at the threshold, reached his hand out, and found that the normal weight pulling it down had gone. He stepped carefully over the threshold and gave a squawk of alarm as his feet left the ground and he drifted up to the ceiling. The others watched in amusement as he bounced gently off the ceiling, drifted slowly down to the floor again, touched the floor with the heel of one foot and began to slowly tumble end over end.

     Then, suddenly, the soldier was screaming in terror. "Falling!" he cried. "I'm falling!" He thrashed around in wild panic while the others shouted reassurances at him, but gradually sanity returned to the soldier as it dawned on him that he'd hardly moved. He was still floating in the corridor, bouncing gently off the walls and ceiling, and he tried to grab hold of something to steady himself. “Don’t just stand there!” he yelled as the others collapsed in helpless laughter. “Do something!”

     “There are handholds in the wall over there,” said Thomas, pointing. “See if you can reach them.”

     The soldier turned his head and saw them, but couldn’t reach them from his position in the middle of the tunnel. He was forced to float helplessly, unable to move or stop his slow rotation, until Kronos’s feeble gravity gradually brought him back down to the ground. As he touched the floor, however, the contact was enough to send him slowly up into the air again and he suffered another bout of slow, lazy bouncing between floor and ceiling, each bounce lasting a full twenty seconds in which he could do nothing but wait for the next contact.

     This time, though, he was also moving sideways towards the left hand wall and eventually he was close enough to grasp one of the handholds with his outstretched hand. Anchored now by one hand, he swung slowly around to face the wall, and when he managed to grab another handhold he was finally able to stabilise himself. The others clapped and cheered, and the soldier breathed a sigh of relief.

     Safe and secure now, Shaun looked down the tunnel and saw four rows of handholds set into walls, spaced at intervals in the walls, floor and ceiling as if they were the rungs of ladders laid on their sides. The floor was no longer flat, and it no longer had walls and ceiling as such. Instead the tunnel was tubular, like the inside of a pipe. There was no need for a flat floor when there wasn’t enough gravity to make walking possible. There was just enough gravity to give them a sense of up and down, though, and Shaun’s legs were slowly pulled down until he was the same way up as the others, still in the airlock.

     He practised moving from one handhold to another and found that it was quite easy, although he had to take care to stop his legs waving all over the place. He thought it’d be a bit easier if he were using the row of rungs set into the curving floor, though, and decided to try and move over to them. The trouble was that they were beyond his reach, which meant that he’d have to launch himself towards them and hope he passed close enough to grab one. If he missed, he’d be left bouncing around like before, but that no longer worried him. Once he'd gotten over the initial shock of it, he’d quite enjoyed it. He took aim, therefore, and gently pushed himself away from the wall with his arms.

     He was lucky and was able to grab the floor rungs with no difficulty. Having stabilised himself again, he then found that he could move up and down the rungs quite easily, with his legs stretched out behind him parallel to the floor, and he decided they’d have no difficulty traversing the almost weightless tunnels. “Okay, I think I’ve got it solved now,” he called back to the others. “It feels like you're falling at first, but then it's just like swimming. Come and have a go.”

     Jerry got down on his hands and knees, took hold of the nearest floor rung and went out after the soldier, followed by Lirenna. Their eyes widened with alarm as they felt their weight leaving, but having seen Shaun overcoming the sensation they were able to remain calm until they also became accustomed to the unnatural feeling. Soon, Lirenna was grinning with delight, but Jerry complained of feeling ill and grabbed hold of the iron rungs, refusing to let go of them.

     “The trouble is that you need both your hands for that,” said Thomas, however. “Suppose we have to cast a spell or something?”

     “You’ll be left floating for a while, that’s all,” replied Lirenna, whose long, dark hair was waving around like seaweed in a slow current. She let go of the rungs for a moment and floated a few inches above the floor while she gathered her hair up with both hands and tied it up in a bun. Diana, watching, did the same. By the time the demi shae had finished tying the knots Kronos’s feeble gravity had pulled her down to bounce gently on the floor, so softly that she barely felt it, and she took hold of the rungs again. “See?” she said. “Floating’s fun!”

     “Yeah, I suppose so,” replied Thomas, following her out of the airlock.

     Diana came after him, and Matthew followed last of all. They stayed close to the airlock for half an hour or so while they got used to moving around in the low gravity, and when they were confident that they’d mastered the basic skills they moved on along the set of rungs in the floor, Shaun in the lead and the others following in the same order as they’d left the airlock.

     Jerry was still complaining of feeling ill, though. "It's like being seasick," he said. "Like when you try to read something while being thrown around in a stormy sea."

     "It'll probably pass," said Shaun, who was feeling fine himself.

     "I hope so."

     The tunnel ran as straight as a pipe, occasionally branching and forking and with entrances to large caverns here and there on either side. They also came across the occasional shaft leading deeper into the small moon with rungs set into the sides, and they stared nervously down into the darkness of the first one they came to.

     “I wonder how far down it goes,” said Diana, peering down over its edge.

     “One way to find out,” said Thomas, staring curiously and hopefully into the depths.

     “No, I don’t think we ought to go down yet,” said Shaun, though. “The moon trogs are down there, and I think we ought to get a bit further from the city first. If the Konnens treat the moon trogs the same way they treated us, they’re likely to be a bit wary of anyone coming from the city. I think we ought to put a bit of distance between us and the city first, and then go down.”

     "I think I'm going to be sick," said Jerry. "I really feel awful."

     Diana swam over to him and put a hand on his head, saying a prayer to Caroli. "How do you feel now?" she asked.

     "Better," replied the tiny nome. "Thanks."

     The others were still staring down the dark shaft. “Suppose you fell down there,” said Matthew. “What would happen to you?”

     Thomas thought for a moment. “Well,” he said eventually, “if the gravity’s five hundred times less than it is back on Tharia, then I suppose that means you can fall five hundred times further without hurting yourself. So, if you can fall, say, five or six feet back home without hurting yourself much, then I suppose you could fall, er, about, er, what is it? Three thousand feet? By the Gods, that’s over half a mile!”

     The others were astonished. “Then you could probably just jump down there,” said Matthew in disbelief.

     “If the shaft’s less than half a mile deep,” replied Thomas. “Don’t forget that Kronos is twenty five miles across. That shaft might go all the way down to the centre.”

     “And even if the shaft is only half a mile deep,” added Shaun, “you'd only land safely if you landed on your feet. If you tumbled on the way down and you hit your head on the side, down near the bottom where you'd be moving fast..." He left the thought unspoken in the air, but the others had a clear picture in their heads and decided unanimously that if they ever did decide to descend the shaft, they'd do it by climbing down the rungs.

     They encountered airlocks every two to three hundred yards, most of them standing open so that they could simply swim through. Shaun was right, thought Thomas as he floated through an open door without touching the sides. It is just like being underwater! A couple of times, though, they came across airlocks that were closed and locked and that had red flags in their windows indicating vacuum on their other sides and they were forced to retrace their ‘steps’ and take another turning. Evidently, the disaster that had struck the city of Kronosia had also affected the caverns to some extent. Either that, or other, similar disasters happened from time to time all over the small moon. As Jerry said to the others, it was rather worrying.