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.