“We came from the great island continent of Atlantis, lying west of the Pillars of Hercules, west of the Strait of Gibraltar, and our city was the first Atlantean colony. Our people pushed south along the African coast, into the Gulf of Guinea, up the Niger river, and thence eastward. Here was their first permanent settlement, and Korakum was a flourishing capital before we dreamed of entering Egypt. History?” said he. “Wait until the world receives the translations of the stories in the Library of Athensi. It is the history of the world before the Flood submerged Atlantis, giving rise to all the legendary stories of the Flood which persist in the literature of all people. It is the history of a mightier civilization, extending farther back into the years, than your wildest dreamers ever conjured out of their imaginations.” Through echoing stone halls of vast breadth and height, up stone stairways, under gaping roofs, for two days, the boys had wandered at will, staring at the shell of that ancient civilization of which Horeb spoke, marvelling at the tremendous labor involved in these buildings, involuntarily dropping their voices to a whisper in the presence of the ghosts of uncounted centuries. But now, on the third day, having seen all there was to see and not being scientists who could pore forever over the meaning of faded and worn inscriptions found here and there upon a fallen block of stone, they were back in the grove, and Frank was seated at the radio and voicing his desire for action, immediate action, looking to the rescue of his chum. This apparatus, devised by the boys working in conjunction in their home laboratories at the Temple and Hampton country homes, adjoining each other, on Long Island, was a duplex sending and receiving station. In it they had departed from the accepted methods of duplex operation, of which the best known is that of Marconi, regulated by a receiver coupled to the coils of a transmitting antenna and a balancing antenna, by means of which one signal may be cut out completely while another is retained undiminished, thus insuring reception and transmission simultaneously. Instead, they had worked out a system whereby the voice exercised full control. When speech was not being used, the set was receptive to messages from other points. But the moment one began to speak, a sluggish contact device consisting of mercury in capillary tube was closed by the vocal vibrations and the set at once thrown into transmission. This controlling device was located in the microphone transmitter, and that it had escaped destruction in the vandalism practised on the set by Professor Souchard’s murderers was little short of a miracle.