rills that ran
gracefully down the glacier, curling and swirling in their shining
channels, and cutting clear sections through the porous surface-ice into
the solid blue, where the structure of the glacier was beautifully
illustrated.

The series of small terminal moraines which I had observed in the
morning, along the south wall of the amphitheater, correspond in every
way with the moraine of this glacier, and their distribution with
reference to shadows was now understood. When the climatic changes came
on that caused the melting and retreat of the main glacier that filled
the amphitheater, a series of residual glaciers were left in the cliff
shadows, under the protection of which they lingered, until they formed
the moraines we are studying. Then, as the snow became still less
abundant, all of them vanished in succession, except the one just
described; and the cause of its longer life is sufficiently apparent in
the greater area of snow-basin it drains, and its more perfect
protection from wasting sunshine. How much longer this little glacier
will last depends, of course, on the amount of snow it receives from
year to year, as compared with melting waste.

After this discovery, I made excursions over all the High Sierra,
pushing my explorations summer after summer, and discovered that what at
first sight in the distance looked like extensive snow-fields, wore in
great part glaciers, busily at work completing the sculpture of the
summit-peaks so grandly blocked out by their giant predecessors.

On August 21, I set a series of stakes in the Maclure Glacier, near
Mount Lyell, and found its rate of motion to be little more than an inch
a day in the middle, showing a great contrast to the Muir Glacier in
Alaska, which, near the front, flows at a rate of from five to ten feet
in twenty-four hours. Mount Shasta has three glaciers, but Mount
Whitney, although it is the highest mountain in the range, does not now
cherish a single glacier. Small patches of lasting snow and ice occur on
its northern slopes, but they are shallow, and present no well marked
evidence of glacial motion. Its sides, however, are scored and polished
in many places by the action of its ancient glaciers that flowed east
and west as tributaries of the great glaciers that once filled the
valleys of the Kern and Owen's rivers.

CHAPTER III

THE SNOW

The first snow that whitens the Sierra, usually falls about the end of
October or early in