“My friends,” said he, “we have now reached the border-land between Atlantis and the outside world. A rim of glass fifty feet thick divides us from the ocean; and that glass, as you know, is composed of dozens of layers, one above the other, several of them strengthened with interwoven strands of fine wire, and all composed of a special pressure-resisting glass devised at the orders of Agripides. You understand, of course, that the wall does not end where you see it, but penetrates five hundred feet underground, lest the ocean overwhelm us from beneath; you also understand that the glass is ribbed with steel, which holds it together in a sort of latticed framework, with girders, beams and stanchions at measured intervals like the metallic skeleton of a great building. “The erection of the wall represents the supreme accomplishment of Atlantean engineering, and required the labor of thirty thousand men for thirty-four years. But Agripides, with his usual foresight, planned it so, that the work, once done, would never require renewal, for glass is one of the most durable of substances, and is virtually immune to dissolution by the ocean waters. We have our immersible vessels, of course, which regularly range the seas around the glass dome in search of any possible fault or fissure; but no serious damage has ever yet been discovered, and it is safe to say that the present edifice will serve us and our descendants for a hundred thousand generations.” The speaker paused, as if for effect; then, noting that his audience remained silent, he concluded, “Is there anyone that would like to ask a question?” “Yes, I would,” I surprised myself by saying. All eyes were bent curiously upon me, and I was forced to continue, “Glass is, as you say, an exceedingly durable substance, but it is also extremely fragile. Is there no possibility that the wall will ever be cracked?” “Cracked?” echoed the tutor, with a surprised smile. “Do you think that, if there had been such a possibility, Atlantis would not have been inundated long ago? Granted, if any very heavy object were to collide with the wall, it might be broken and we would be flooded out like ants. But how could there be any such heavy object here in the deep sea? Certainly, the fishes couldn’t break through.” “No, of course not,” I conceded, feeling that I had made myself ridiculous--and with that the discussion ended. But my words were often to be recalled to me in the tempestuous days that followed; and more than one of my hearers was to speak of them as strangely prophetic. For the next hour we followed a little path that clung close to the glass wall. And, as we proceeded, my impression of its opaqueness was dissipated, for from time to time a little flickering light was momentarily visible beyond the green thicknesses; and I had disturbing remembrances of the lantern-bearing fishes that had haunted us on our way to Atlantis.