The Dark Design by Phillip Jose Farmer

“It’s 9753 meters high! That’s taller than Mount Everest!”

There was good reason for him to groan and the others to look disturbed. The airship could not go higher than 9144 meters, and Firebrass would hesitate to take it to that altitude. Theoretically, that was the pressure height of the gas cells. To go above that meant that the automatic valves on top of the cells would release hydrogen. If they did not do so, the cells would explode, having reached their inflation limit.

Firebrass would not like to take the vessel near the pressure height. An unexpectedly warm layer of air could cause the hydrogen in the cells to expand even more, thus making the ship more buoyant than was safe. Under those conditions, the Parseval would rise swiftly. The pilot would have to act swiftly, pointing the vessel’s nose down and also tilting the propellers to give a downward drive. If this maneuver failed, the gas, expanding under the lessened atmospheric pressure, would stretch the cell walls to the rupture point.

Even if the ship got through this situation, its loss of valved-off gas would mean that it would become heavy. The only way to lighten the ship would be to discharge ballast. If too much ballast was dropped, the Parseval would be too buoyant.

Firebrass said, “If it’s like this all the way around, we’re screwed. But Joe said . . .”

He stood for a moment, thinking, watching the dark, ominous mass gradually swell. Below them the Valley wriggled snakily, eternally covered with fog in this cold area. They had long ago passed the last of the double line of grailstones. Yet the radar and the infrared equipment showed that thick, high vegetation grew on the hills. One more mystery. How could trees flourish in the cold mists ?

Firebrass said, “Take her down to 3050 meters, Cyrano. I want to get a good look at the headwaters.”

By “look” he meant a radar view. No one could see through the massive, boiling clouds covering the mighty hole at the base of the mountains. Bat radar showed a colossal exit for The River, an opening 4.9 kilometers or a little over 3 miles wide. The highest point of the arch was 3.5 kilometers.

The mighty flood rushed straight for 3 kilometers, then tumbled over the edge of a cliff and fell straight for 915 meters, over 3000 feet.

“Joe may have been exaggerating when he said you could float the moon on The River where it comes out of the cave,” Firebrass said, “but it is impressive!”

“Yes,” Cyrano said, “it is indeed grand. But the air here is almighty rough.”

Firebrass ordered the Parseval to a higher altitude and on a course which would parallel the mountain at a distance of 12 kilometers. Cyrano had to crab the dirigible and swivel the propellers to keep from being blown south, and it crept alongside the towering range.

Meanwhile, the radio operator tried to get into contact with the Mark Twain.

“Keep it up,” Firebrass said. “Sam’11 want to know how we’re doing. And I’m interested in finding out how the Minerva made out.”

To the others he said, “I’m looking for that gap in the mountains. There has to be one. Joe said the sun momentarily flashed through a hole or what he thought was a hole. He couldn’t see the break, but since the sun never gets more than halfway up the horizon here, it couldn’t shine inside the sea unless there’s a break that starts at ground level.

Jill wondered why They would have erected such a mighty barrier only to leave an opening.

At 15:05, radar reported that there was a break in the verticality. Now the airship was over mountains outside the main wall. These mountains were not the continuous process surrounding the sea but were peaks, some of which reached 3040 meters. Then, as they came closer to the break, they saw that between the lesser mountains and the wall was an immense valley.

“A veritable Grand Canyon, as you have described it to me,” Cyrano said. “A colossal chasm. No one could get down its walls unless he used a rope 610 meters long. Nor could he ever get up the other wall. It is of the same altitude and its sides are as smooth as my mistress’ bottom.”