, its white, pearly bosses relieved by gray and pale
purple shadows in the hollows, and showing outlines as keenly defined as
those of the glacier-polished domes. In less than an hour it attains
full development and stands poised in the blazing sunshine like some
colossal mountain, as beautiful in form and finish as if it were to
become a permanent addition to the landscape. Presently a thunderbolt
crashes through the crisp air, ringing like steel on steel, sharp and
clear, its startling detonation breaking into a spray of echoes against
the cliffs and canon walls. Then down comes a cataract of rain. 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. One soon becomes so
accustomed to see them that the noon sky seems empty and abandoned
without them, as if Nature were forgetting something. When the glorious
pearl and alabaster clouds of these noonday storms are being built I
never give attention to anything else. No mountain or mountain-range,
however divinely clothed with light, has a more enduring charm than
those fleeting mountains of the sky--floating fountains bearing water
for every well, the angels of the streams and lakes; brooding in the
deep azure, or sweeping softly along the ground over ridge and dome,
over meadow, over forest, over garden and grove; lingering with cooling
shadows, refreshing every flower, and soothing rugged rock-brows with a
gentleness of touch and gesture wholly divine.

The most beautiful and imposing of the summer storms rise just above the
upper edge of the Silver Fir zone, and all are