As a minor detail of the vast complex of storm, the pocket of old polar air which had intruded itself into the tropical air had continued to move toward the California coast. It was only a few hundred miles in diameter; nevertheless, it possessed almost explosive potentialities. It was warm and moist below and extremely cold and dry above. If anything contrived to force the lower layer upward, this air would cool as it rose, but still would remain warmer than the air of any particular level at which it arrived. It would therefore continue to rise more and more rapidly.

The first of the old polar air to reach the coast was a narrow wedge which lay beneath the last of the warm tropical air and so was prevented from rising. About three hours before daybreak, however, the full depth of old polar air arrived, and mountains of the Coast Range cast the lower level upward; immediately, as if a match had been touched to shavings soaked in gasoline, the reaction within the air itself became spontaneous. Great towers of cumulus cloud, miles in circumference, ascended higher and higher, billowing outward. From this rising air the rain, hard-drumming in great drops, poured in cloudburst torrents. But here and there the upper current was so strong that it carried the falling rain aloft and swirled it about until the drops froze and at last fell as hail. Close to the ground the air was sucked in violently, as toward a vacuum, to fill in behind the rising air; the sudden wind-flaws drove the rain before them, and snapped branches from trees. The disturbed electrical balance readjusted itself in stabs of lightning; thunder boomed above the roar of wind and rain.

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With the staccato rattle of drums sounding an alarm, the heavy drops beat upon thousands of windows. Shades flapped, curtains bellied out, water spattered upon floors. Thousands of people woke from the death-like sleep which comes before the dawn. Still drugged with oblivion, men staggered to close half-opened windows. Mothers hurried to look at their babies. Children screamed in fright at the sudden uproar. (As thousands of lights were snapped on, the operator at French Bar Power-House, two hundred miles away, spun his handle and let more water pass through the turbines to meet the sudden demand for current.)

The General Manager awoke. He thought of his thousands of miles of rails gleaming wet in the night, of the waters running in the ditches beside the tracks, of the culverts and the bridges. He remembered the streamliner, somewhere out in Nevada, coming fast. He thought also of the men and the safety devices, of the snow-plows at work, of the red and green lights shining through falling rain and snow. He had confidence, and went back to sleep.