Time after time Kemal would cycle through the up-and-down fluctuations of the Red Sea, watching as the average sea level actually rose toward the end of the Ice Age. He always stopped, of course, at the abrupt jump in sea level that marked the rejoining of the Red Sea and the Indian Ocean. After that, the Red Sea was useless for his purposes, since its sea level was tied to that of the great world ocean.

The echo of Schliemann inside Kemal's mind made him think: What a flood that must have been.

What a flood. The Ice Age had locked up so much water in glaciers and ice sheets that the sea level of the whole world fell. It eventually reached a low enough point that land bridges arose out of the sea. In the north Pacific, the Bering land bridge allowed the ancestors of the Indies to cross on foot into their great empty homeland. Britain and Flanders were joined. The Dardanelles were closed and the Black Sea became a salty lake. The Persian Gulf disappeared and became a great plain cut by the Euphrates. And the Bab al Mandab, the strait at the mouth of the Red Sea, became a land bridge.

But a land bridge is also a dam. As the world climate warmed and the glaciers began to release their pent-up water, the rains fell heavily everywhere; rivers swelled and the seas rose. The great south-flowing rivers of Europe, which had been mostly dry during the peak of glaciation, now were massive torrents. The Rhone, the Po, the Strimon, the Danube poured so much water into the Mediterranean and the Black Sea that their water level rose at about the same rate as that of the great world ocean.

The Red Sea had no great rivers, however. It was, in geological terms, a new sea, formed by rifting between the new Arabian plate and the ancient African, which meant it had uplift ridges on both coasts. Many rivers and streams flowed from those ridges down into the Red Sea, but none of them carried much water compared to the rivers that drained vast basins and carried the melt-off of the glaciers of the north. So, while the Red Sea gradually rose during this time, it lagged far, far behind the great world ocean. Its water level responded to the immediate local weather pattems rather than to worldwide weather. Until one day the Indian Ocean rose so high that tides began to spill over the Bab al Mandab. The water cut new channels in the grassland there. Over a period of several years, the leakage grew, creating a series of large new tidal lakes on the Hanish Plain. And then one day, some fourteen thousand years ago, the flow cut a channel so deep that it didn't dry up at low tide. The water kept running through it, cutting the channel deeper and deeper, until those tidal lakes were fall, and brimmed over. With the weight of the Indian Ocean behind it the water gashed into the basin of the Red Sea in a vast flood that in a few hours brought the Red Sea up to the level of the world ocean.

This isn't just the boundary marker between useful and useless water level data, thought Kemal. This is a cataclysm, one of the rare times when a single event changes a vast area in a period of time short enough that human beings could notice it. And, for once, this cataclysm happened in an era when human beings were there. It was not only possible but likely that someone saw this flood -- indeed, that it killed many, for the southern end of the Red Sea basin was rich savanna and marshland up to the moment when the ocean broke through, and surely the humans of fourteen thousand years ago would have hunted there. Would have gathered seeds and fruits and berries there. Some hunting party must have seen, from the peaks of the Dehalak Mountains, the great walls of water that roared up the plain, breaking and parting around the slopes of the Dehalaks, making islands of them.

Such a hunting party would have known that their families had been killed by this water. What would they have thought? Surely that some god was angry with them. That the world had been done away, buried under the sea. And if they survived, if they found a way to the Eritrean shore after the great turbulent waves settled down to the more placid waters of the new, deeper sea, they would tell the tale to anyone who would listen. And for a few years they could take their hearers to the water's edge, show them the treetops barely rising above the surface of the sea, and tell them tales of all that had been buried under the waves.

Noah, thought Kemal. The immortal Utnapishtim, the flood survivor that Gilgamesh visited. Ziusudra of the Sumerian flood story. Atlantis. The stories were believed. The stories were remembered. In time the tellers of the tale forgot where it happened -- they naturally transposed the events to locations that they knew. But they remembered the things that mattered. What did the flood story of Noah say? Not just rain, no, it wasn't a flood caused by rain alone. The "fountains of the great deep" broke open. No local flood on the Mesopotamian plain would cause that image to be part of the story. But the great wall of water from the Indian Ocean, coming on the heels of years of steadily increasing rain -- that would bring those words to the storytellers' lips, generation after generation for ten thousand years until they could be written down.

As for Atlantis, everyone was so sure they had found it years ago. Santorini -- Thios -- the Aegean island that blew up. But the oldest stories of Atlantis said nothing of blowing up in a volcano. They spoke only of the great civilization sinking into the sea. The supposition was that later visitors came to Santorini and, seeing water where an island city used to be, assumed that it had sunk, knowing nothing of the volcanic eruption. To Kemal, however, this now seemed far-fetched indeed, compared to the way it would have looked to the people of Atlantis themselves, somewhere on the Massawa Plain, when the Red Sea seemed to leap up in its bed, engulfing the city. That would be sinking into the sea! No explosion, just water. And if the city were in the marshes of what was now the Massawa Channel, the water would have come not just from the southeast but from the northeast and the north as well, flowing among and around the Dehalak mountains, making islands of them and swallowing up the marshes and the city with them.

Atlantis. They were not beyond the pillars of Hercules, but Plato was right to associate the city with a strait. He, or whoever told the tale to him, simply replaced the Bab al Mandab with the greatest strait that he had heard of. The story might well have reached Plato by way of Phoenicia, where Mediterranean sailors would have made the story fit the sea they knew. They learned it from Egyptians, perhaps, or nomad wanderers from the hinterlands of Arabia, or perhaps it was already latent within every old-world culture by then; and "within the straits of Mandab" would have become "within the pillars of Hercules," and then, because the Mediterranean itself was not strange and exotic enough, the locale was moved outside even that strait.

All these suppositions came to Kemal with the absolute certainty that they were true, or nearly true. He rejoiced at the thought of it: There was still an ancient civilization left to discover.

But if it was there, why hadn't Pastwatch found it? The answer was simple enough. The past was huge, and while the TruSite I had been used to collect climatological information, the new machines that were precise enough to track individual human beings would never have been used to look at oceans where nobody lived. Yes, the Tempoview had explored the Bering Strait and the English Channel, but that was to track long-known-of migrations. There was no such migration in the Red Sea. Pastwatch had simply never looked through their precise new machines to see what was under the water of the Red Sea in the waning centuries of the last Ice Age. And they never would look, either, unless someone gave them a compelling reason.