For a certain section of canyon-rim above the South Fork of the Yuba River the hour approached. Neither accident nor the work of man was involved. The area was uninhabited. It offered foothold to few trees, and had never been lumbered. Its quartz yielded no gold. On the bare outcroppings, forest fires died for lack of fuel. But through centuries the river had worn at the base of the canyon-wall, and the side-gulches had grown deeper. At last the flowing water in one of the gulches finished washing away a little sand, and a tall rock shifted a quarter of an inch. The earth was already heavy with soaked-up rain. This small movement of the foundation unloosed the whole mass. With a long roar four million tons of the canyon-rim—rock, soil, chaparral—slid down five hundred feet before again coming to rest. Through trees and undergrowth masses of rock crashed a thousand feet farther until they reached the river-bed, and clogged the flow of the stream. Halfway down the canyon-side a tall cedar rooted in the slide stood leaning drunkenly.

In the valleys rain was falling. As it soaked through the earth, it leached away salts; rapaciously, the gnaw of its acidity ate even at solid limestone. By its buoyancy it floated away fallen leaves and seeds, pods and bark-scalings; as the water rose, logs and up-rooted trees yielded to the strange upward pull; they lifted from the mud where gravity had held them, and began the journey toward the sea-bottom.

Now swiftly, now more slowly, the water flowed always onward and downward at the pull of the earth’s center. In the torrents of the stream beds, it moved boulders before it. The same force worked subtly in every turbid trickle which held some clay in suspension or rolled a little fine sand along with it.

Whether the cut or gully was man-made or “natural” was no concern of the rain. Here and there occurred a land-slip. Of much greater importance was the continual unheeded fall of loosened gravel and small stones. Blue clay soaked up until it grew soft, and flowed by its own weight, oozing slowly forward like hot candy poured upon a platter. On hillsides the adobe soil grew heavy until great sections settled and slid, leaving behind them wide crescent-shaped scars of raw earth. And always the movement was downward, from the hill-tops toward the sea.

3

Along by Fox Farm was a stretch of highway that was in pretty bad shape that night. A rotary was working on it. The men in the rotary could see next to nothing; the flying snow reflected the lights right back in their faces. They were feeling their way along from snowstake to snowstake. Then came a bang, and a jolt, and the shear-bolts went.

“That’s no pebble,” said the swamper, and they both piled out into the snow, expecting to find that a boulder or tree-trunk had fallen down on the highway.