was slow, as
we count time, and is still going on, north and south, over all the
world wherever glaciers exist, whether in the form of distinct rivers,
as in Switzerland, Norway, the mountains of Asia, and the Pacific Coast;
or in continuous mantling folds, as in portions of Alaska, Greenland,
Franz-Joseph-Land, Nova Zembla, Spitzbergen, and the lands about the
South Pole. But in no country, as far as I know, may these majestic
changes be studied to better advantage than in the plains and mountains
of California.

Toward the close of the glacial period, when the snow-clouds became less
fertile and the melting waste of sunshine became greater, the lower
folds of the ice-sheet in California, discharging fleets of icebergs
into the sea, began to shallow and recede from the lowlands, and then
move slowly up the flanks of the Sierra in compliance with the changes
of climate. The great white mantle on the mountains broke up into a
series of glaciers more or less distinct and river-like, with many
tributaries, and these again were melted and divided into still smaller
glaciers, until now only a few of the smallest residual topmost branches
of the grand system exist on the cool slopes of the summit peaks.

Plants and animals, biding their time, closely followed the retiring
ice, bestowing quick and joyous animation on the new-born landscapes.
Pine-trees marched up the sun-warmed moraines in long, hopeful files,
taking the ground and establishing themselves as soon as it was ready
for them; brown-spiked sedges fringed the shores of the newborn lakes;
young rivers roared in the abandoned channels of the glaciers; flowers
bloomed around the feet of the great burnished domes,--while with quick
fertility mellow beds of soil, settling and warming, offered food to
multitudes of Nature's waiting children, great and small, animals as
well as plants; mice, squirrels, marmots, deer, bears, elephants, etc.
The ground burst into bloom with magical rapidity, and the young forests
into bird-song: life in every form warming and sweetening and growing
richer as the years passed away over the mighty Sierra so lately
suggestive of death and consummate desolation only.

It is hard without long and loving study to realize the magnitude of the
work done on these mountains during the last glacial period by glaciers,
which are only streams of closely compacted snow-crystals. Careful study
of the phenomena presented goes to show that the pre-glacial