A wave, a ripple of light, a trembling and turning of the aspen leaves, like the approach of a breeze on the water, crossed the valley from the west; and the lull and the deadly stillness and the sultry air passed away on a cool wind. The night bird of the cañon, with clear and melancholy notes announced the twilight. And from all along the cliffs rose the faint murmur and moan and mourn of the wind singing in the caves. The bank of clouds now swept hugely out of the western sky. Its front was purple and black, with gray between, a bulging, mushrooming, vast thing instinct with storm. It had a dark, angry, threatening aspect. As if all the power of the winds were pushing and piling behind, it rolled ponderously across the sky. A red flare burned out instantaneously, flashed from the west to east, and died. Then from the deepest black of the purple cloud burst a boom. It was like the bowling of a huge boulder along the crags and ramparts, and seemed to roll on and fall into the valley to bound and bang and boom from cliff to cliff. “Oh!” cried Bess, with her hands over her ears. “What did I tell you?” “Why, Bess, be reasonable!” said Venters. “I’m a coward.” “Not quite that, I hope. It’s strange you’re afraid. I love a storm.” “I tell you a storm down in these cañons is an awful thing. I know Oldring hated storms. His men were afraid of them. There was one who went deaf in a bad storm, and never could hear again.” “Maybe I’ve lots to learn, Bess. I’ll lose my guess if this storm isn’t bad enough. We’re going to have heavy wind first, then lightning and thunder, then the rain. Let’s stay out as long as we can.” The tips of the cottonwoods and the oaks waved to the east, and the rings of aspens along the terraces twinkled their myriad of bright faces in fleet and glancing gleam. A low roar rose from the leaves of the forest, and the spruces swished in the rising wind. It came in gusts, with light breezes between. As it increased in strength the lulls shortened in length till there was a strong and steady blow all the time, and violent puffs at intervals, and sudden whirling currents. The clouds spread over the valley, rolling swiftly and low, and twilight faded into a sweeping darkness. Then the singing of the wind in the caves drowned the swift roar of rustling leaves; then the song swelled to a mourning, moaning wail; then with the gathering power of the wind the wail changed to a shriek. Steadily the wind strengthened and constantly the strange sound changed. The last bit of blue sky yielded to the on-sweep of clouds. Like angry surf the pale gleams of gray, amid the purple of that scudding front, swept beyond the eastern rampart of the valley. The purple deepened to black. Broad sheets of lightning flared over the western wall. There were not yet any ropes or zigzag streaks darting down through the gathering darkness. The storm center was still beyond Surprise Valley.