The big drops sift through the pine-needles, plash and patter on the granite pavements, and pour down the sides of ridges and domes in a network of gray, bubbling rills.

In a few minutes the cloud withers to a mesh of dim filaments and disappears, leaving the sky perfectly clear and bright, every dust-particle wiped and washed out of it.

Everything is refreshed and invigorated, a steam of fragrance rises, and the storm is finished--one cloud, one lightning-stroke, and one dash of rain.

This is the Sierra mid-summer thunder-storm reduced to its lowest terms.

But some of them attain much larger proportions, and assume a grandeur and energy of expression hardly surpassed by those bred in the depths of winter, producing those sudden floods called "cloud-bursts," which are local, and to a considerable extent periodical, for they appear nearly every day about the same time for weeks, usually about eleven o'clock, and lasting from five minutes to an hour or two.