Then they thanked the foresight that had led them to build up a roof-touching fuel reserve, a store of fresh produce and game, for they could not leave their refuge. They were snowbound until Titan left the shadow of Saturn and the warmth should again melt their prison walls. But those days were not days of idleness; they were days of accomplishment. The women, under 'Tina's guidance, ripped apart unneeded goods salvaged from the skiff's stores--tarpaulins, extra bedding and napery, carpeting, drapes--and restitched them into more needed, more practical articles of wearing and household apparel. * * * * * Breadon and Greg, laying aside a mutely-acknowledged hostility, pooled their knowledge and ingenuity in an effort to ascertain their whereabouts on the satellite. Neither had studied mathematics closely, a fact each now bewailed. But they had a few books on astrogation, taken from the skiff, and they had determination and intelligence. Utilizing some of their precious, dwindling store of forged metal, they constructed a crude but--they believed--reasonably accurate sextant with which, when the darkness was gone, they hoped to take celestial readings that would aid their computations. In the making of this, Greg was forced to sacrifice something that had been for almost ten years as much a part of him as his arms and legs. His spectacles. Strangely, he did not miss them much after the first day. Their purpose had been mainly to protect him from eyestrain and headaches in a confined vocation that required much reading. But here on Saturn's satellite, health improved by hard labor, Greg had experienced no headaches. He was, in fact, almost disgustingly healthy. He could tell by the straining of his clothes at throat and chest and waist-band that he was gaining weight; his appetite had improved and when night came, he did not have to read himself to sleep. Young Tommy took upon himself the task of chronicling their exile. His method, though extravagantly romantic as befitted his years and enthusiasm for this adventure, was nonetheless efficient. He laboriously scraped smooth a wide portion of the cave-wall; on this he inscribed a calendar, a log, and a map of such portions of the satellite as they had so far explored. Meanwhile Sparks Hannigan fretted over his damaged radio set. An accomplished bug-pounder, he took little time to get the wiring rearranged. The replacement of metal parts was a tougher problem, but it, too, he solved with the aid of their acetylene torch. One final job, however, stopped him cold. He shook his head when he spoke of it to Malcolm. "The tubes, Greg. It just ain't no use. We can't operate the radio less'n we got tubes, and ours is gone. I guess I'm just wasting my time." Greg said, "Isn't there a type of radio that works without tubes? Operates on a crystal, or something?"