The mist was heavy and thick, and through it the flying creatures darted upon their innumerable businesses, visible for an instant in all their colorful beauty, then melting slowly into indefiniteness as they sped away. The tribefolk on the clustered rafts watched them as they darted overhead, and for hours the little squadron of fungoid vessels floated slowly through the central channel of the marsh. The river had split into innumerable currents which meandered purposelessly through the glistening black mud of the swamp, but after a long time they seemed to reassemble, and Burl could see what had caused the vast morass. Hills appeared on either side of the stream, which grew higher and steeper, as if the foothills of a mountain chain. Then Burl turned and peered before him. Rising straight from the low hills, a wall of high mountains rose toward the sky, and the low-hanging clouds met their rugged flanks but half-way toward the peaks. To right and left the mountains melted into the tenuous haze, but ahead they were firm and stalwart, rising and losing their heights in the cloud-banks. They formed a rampart which might have guarded the edge of the world, and the river flowed more and more rapidly in a deeper and narrower current toward a cleft between two rugged giants that promised to swallow the water and all that might swim in its depths or float upon its surface. Tall, steep hills rose from either side of the swift current, their sides covered with flaking molds of an exotic shade of rose-pink, mingled here and there with lavender and purple. Rocks, not hidden beneath a coating of fungus, protruded their angular heads from the hillsides. The river valley became a gorge, and then little more than a cañon, with beetling sides that frowned down upon the swift current running beneath them. The small flotilla passed beneath an overhanging cliff, and then shot out to where the cliffsides drew apart and formed a deep amphitheater, whose top was hidden in the clouds. And across this open space, on cables all of five hundred feet long, a banded spider had flung its web. It was a monster of its tribe. Its belly was swollen to a diameter of no less than two yards, and its outstretched legs would have touched eight points of a ten-yard circle. It was hanging motionless in the center of the colossal snare as the little group of tribefolk passed underneath, and they saw the broad bands of yellow and black and silver upon its abdomen. They shivered as their little crafts were swept below. Then they came to a little valley, where yellow sand bordered the river and there was a level space of a hundred yards on either side before the steep sides of the mountains began their rise. Here the cluster of mushroom rafts were caught in a little eddy and drawn out of the swiftly flowing current. Soon there was a soft and yielding jar. The rafts had grounded.