In four hours the duplicate record came back, restored as completely as possible, but there were long blanks which were un-intelligible. Underwood turned up the maximum radiation which helped bring out the characters, but also burned them rapidly away if left on too long. Suddenly he caught his breath. "Listen to this: 'Our bearings are now 6749367 Sirenia, having traveled 84 _tre-doma_, Sirenia. In two _te-ela_ we land. Perhaps for the last time--'" "That's it!" Phyfe exclaimed. "All but the key to their co-ordinate system," said Underwood. "Do you see any possibility of interpreting it, Dreyer?" The semanticist shook his head. "It must be based upon entirely arbitrary reference points as ours is. I see no hope of interpretation with the figures we now have. Perhaps our astronomers could suggest something." Masterson and Ebert, the two astronomers included in the group, were called in from their task of preparing star charts of the Universe of half a million years ago. They considered the facts Underwood presented. Masterson said, "I'm afraid the bearings given by the Sirenians won't be much help. The distance is of value. That shows us that we have a shell at a radial distance of approximately ninety million light years from the Solar System. At best, then, we have this shell, which may be considered as several thousand light years thick, in which to search. If we could find even approximately the proper sector of this shell, we might soon isolate the possible planetary systems to which the Dragbora and Sirenians belonged, but without being able to narrow down the possible sectors of that shell, it becomes an impossible task. Just a single reference to some Island Universe that we might identify would do it, perhaps." Underwood and Dreyer had to agree. They had gained something; if they could just obtain one more scrap of astronomical information, it might give them the key. The search for that key went on among the records and artifacts. The repository itself was searched inch by inch--and still almost none of the artifacts found there could be identified or explained. Apart from the repository, most of the material they had was native to the planet on which the Sirenians landed. By the eighth day Mason's crew had managed to construct equipment for throwing a force shell about the _Lavoisier_, and Underwood breathed considerably easier. They could travel indefinitely behind the protection of that impenetrable shield. Data for navigation was obtained through almost infinitesimal pilot units set outside the shell and connected through hair-fine leads running through equally small holes in it. * * * * *