“The very last,” Highjohn soothed him, “and not rough, even though it’s a bit steep. One of the unreconstructed gorfs who piloted Tanu barges through here back in the earliest days of the time-portal named the thing la Glissade Formidable. Sounds classier than the Dreadful Slide, so that’s what we call it today, too.”

Stein, sitting in a seat beside Sukey, looked puzzled. “But we should be in the Rhône delta now. Bang on the Mediterranean shore. What kind of gradient can there be?”

“You’re in for a surprise,” Bryan told him. “I couldn’t believe it myself when the skipper explained it to me. I used to sail the Med, too, you’ll remember. What it adds up to, Stein, is a slight miscalculation on the part of the boffins who drew up our Pliocene maps.”

The workman installing the transparent panels gave the last one a smack and said, “You’re off, Cap’n!”

“Belt in, everyone,” Highjohn ordered. “You come forward, Bryan. You’re gonna love this one.”

A light wind sprang up as they puttered away from the moorage, following in the wake of a thirty-meter barge loaded with metal ingots. The vapors that had obscured their view finally dissipated, and they looked to the south for a first glimpse of the sea.

They saw a cloud.

“What the hell is that?” Stein wondered. “Looks like a plass factory on fire or a big volcano vent. Friggerty cloud goes clear to the tropopause.”

The mast of the riverboat folded and withdrew, and the auxiliary engine cut out. They began to pick up speed. The clumps of marsh grass were more widely spaced now, and the boat followed a marked channel that trended southeastward, close beneath a rounded headland on their left that jutted into the flats as an outlier of the alpine foothills. They were heading directly toward the towering white cloud, picking up speed every minute.

And then Elizabeth said, “Dear Lord. The Mediterranean is gone.”

The barge that was traveling about half a kilometer ahead of them dropped out of sight. To the east and west along the horizon were low points of land, but between them was only a line of water meeting milky sky, having a shallow dip in the center. And there was a sound, a swelling rumble with a hissing component that grew to deafening proportions as they swept closer and closer to la Glissade Formidable, where the wide expanse of the Rhône ended at the continental brink.

Creyn’s mental voice rang in the brains of all the torc-wearers. “Shall I program oblivion?” But they all replied, “No!” for their curiosity was greater than any terror of what lay ahead.

The boat raced over the edge and started down, borne on muddy waters cascading over a steep fan of sediment, plunging at eighty kilometers an hour into the depths of the Empty Sea.

They came to the end of the Glissade after four hours and floated in the pale waters of a great bitter lake. All around them were the many-colored rocks of the continental roots and glistening, fantastically eroded shapes of salt and anhydrite and gypsum. With its bubble panels stowed away, the boat spread its sail and raced along toward the southwest, for it was there that Creyn told them that the capital city of Muriah lay, at the tip of the Balearic Peninsula, which the Tanu called Aven, above the perfect flat of the White Silver Plain.

They traveled for one more day, overcome by the strangeness and the beauty and hardly able to talk about it except for endless exclamations in both the vocal and mental speech, to which Creyn responded, “Yes, it is wonderful. And more to come, more splendid than you can imagine.”

In the late evening of the sixth day after they had departed from Castle Gateway they arrived. The high peninsula of Aven stretched away into the west, green and rolling, with a single peak near its tip and other eminences half-hidden in haze. A team of helladotheria in glowing trappings of rainbow fabric pulled the boat up a long rollered way while chaliko-riders dressed in gauzy robes and glass armor, bearing lights, animal-headed horns and banners, followed along the steep towpath. The welcoming Tanu sang all the way to the blazing city high above the salt. Their song had a haunting melody that seemed strangely familiar to Bryan; but those human beings who wore the torc were able to understand the alien words:

The giant sequoia had endured for 10,000 years. Standing amidst a grove of lesser specimens high in the Vosges, it was hollowed by ancient wildfire and rot. In millennia past lightning had sheared its top, so that the Tree was only about 100 meters in height; the trunk nearest the ground spanned fully a fourth of that distance, giving the sequoia the appearance of a huge truncated pylon. That it lived at all was evidenced only by sparse branches writhing at the broken crown, their small needles seemingly incapable of photosynthesizing enough sugar to nourish such a monument.

The sequoia was host to a family of fire-backed eagles and several million carpenter ants. Since early in the afternoon it had also harbored a band of freeliving humans who were accustomed to use the great hollow trunk as a safe-house in times of particular danger.

A thin rain fell. In another hour it would be dark. A woman in a water-stained doeskin cloak stood beside one buttress of the great bole, her eyes shut, her fingertips pressed to her throat. After five minutes had passed, she opened her eyes and wiped some of the moisture from her forehead. Stooping, she pulled aside the fronds of a large fern and entered an inconspicuous opening, a nearly healed fissure that led into the interior of the Tree.

Someone helped her out of the sodden cloak. She nodded her thanks. All around the inner perimeter of the trunk small fires burned on low stone platforms, their smoke plumes plaiting together with that of a larger central blaze and rising toward the natural chimney high above. The main fire was laid on a great X-shaped hearth. Its flames towered at the center and diminished to a comfortable cooking height at the ends of the arms. People were gathered around the central fire in great numbers; smaller groups huddled near the subsidiary fireplaces. The place smelt of steaming clothing spread before the flames, of baking ash-bread and pots of hot spiced wine, and of simmering meat stew.