it yet remains a telling monument of the action
of the great glaciers that brought it to light. Its entire surface is
still covered with glacial hieroglyphics whose interpretation is the
reward of all who devoutly study them.

Chapter 11

The Ancient Yosemite Glaciers:
How the Valley Was Formed

All California has been glaciated, the low plains and valleys as well
as the mountains. Traces of an ice-sheet, thousands of feet in thickness,
beneath whose heavy folds the present landscapes have been molded, may
be found everywhere, though glaciers now exist only among the peaks of
the High Sierra. No other mountain chain on this or any other of the
continents that I have seen is so rich as the Sierra in bold, striking,
well-preserved glacial monuments. Indeed, every feature is more or
less tellingly glacial. Not a peak, ridge, dome, canyon, yosemite,
lake-basin, stream or forest will you see that does not in some way
explain the past existence and modes of action of flowing, grinding,
sculpturing, soil-making, scenery-making ice. For, notwithstanding the
post-glacial agents--the air, rain, snow, frost, river, avalanche,
etc.--have been at work upon the greater portion of the Range for tens
of thousands of stormy years, each engraving its own characters more
and more deeply over those of the ice, the latter are so enduring and
so heavily emphasized, they still rise in sublime relief, clear and
legible, through every after-inscription. The landscapes of North
Greenland, Antarctica, and some of those of our own Alaska, are still
being fashioned beneath a slow-crawling mantle of ice, from a quarter
of a mile to probably more than a mile in thickness, presenting noble
illustrations of the ancient condition of California, when its sublime
scenery lay hidden in process of formation. On the Himalaya, the
mountains of Norway and Switzerland, the Caucasus, and on most of those
of Alaska, their ice-mantle has been melted down into separate glaciers
that flow river-like through the valleys, illustrating a similar past
condition in the Sierra, when every canyon and valley was the channel
of an ice-stream, all of which may be easily traced back to their
fountains, where some sixty-five or seventy of their topmost residual
branches still linger beneath protecting mountain shadows.

The change from one to another of those glacial conditions was slow as
we count time. When the great cycle of snow years, called the Glacial
Period,