The area was free of contamination. The boys found walking quite awkward at first and laughed at their own clumsy efforts as they fairly danced along through the volcanic and meteoric dust. There was quite a difference between being absolutely weightless in magnetic-soled shoes and being of one-sixth Earth weight without such shoes. They finally got the hang of it and found they could take gliding steps of about five feet at a time. They kept behind rocks and ground rises to minimize the chance of their being seen. They still could not be certain Kalmus had not seen the _Northern Cross_ come down. The rocks and ground were covered with a down of hoarfrost. This was due to Luna’s scant moisture content condensing in the exceedingly rare atmosphere which was made up principally of carbon dioxide. As they moved along, Rock saw that Shep was beginning to grow a whitish fuzz of dry ice on his suit. It was hard for Rock to realize that the temperature around them was several hundred degrees below zero, while only a scant mile or two farther out it was hotter than boiling water under the full rays of the sun. This was only one of Luna’s many strange features that fascinated him. He wished this had been a trip of exploration and fun instead of the grim battle that it was. As they approached the great rift in the ground, Rock began to get a queasy feeling. “Wide, isn’t it?” he asked Shep over his suit radio. “And deep,” Shep replied, after a look over the brink that had showed no bottom. They brought the ladder over to the edge and carefully spanned the gulf with it. “It just does make it!” Rock gasped. “There’s only about a foot to spare on each end.” They found a wedge of rock like a dinosaur’s tooth deeply embedded in the ground not far from the crack. Around this they tied one end of their safety rope. Then Rock tied the other end around his waist. “Hold on to the ladder to make sure it doesn’t slip,” Rock told his friend, and slowly he started out over the plunging abyss. Rock looked down through the rungs at the black emptiness below. Although he wore the safety line, a fall could be dangerous. He looked ahead as he kept moving forward. The other end of the ladder was wobbling back and forth. When he reached the opposite side of the brink and climbed onto firm ground, he was aware only of the perspiration trickling down his face. It made him turn down his suit heat a couple of degrees. He untied the safety line and threw it back to Shep. Then his friend started over the perilous bridge, with Rock holding his side of the ladder as firm as he was able. Shep made it safely too, so they were both vastly relieved. “We’ll just leave the ladder in place,” Rock suggested, then added gravely, “That’s in case we have to cross it in a hurry.”