isted in the Sierra. And though never perhaps seen by
human eye, it was but yesterday, geologically speaking, since it
disappeared, and the traces of its existence are still so fresh, it may
easily be restored to the eye of imagination and viewed in all its
grandeur, about as truly and vividly as if actually before us. Now we
find that the detritus which fills this magnificent basin was not
brought down from the distant mountains by the main streams that
converge here to form the river, however powerful and available for the
purpose at first sight they appear; but almost wholly by the small local
tributaries, such as those of Indian Canon, the Sentinel, and the Three
Brothers, and by a few small residual glaciers which lingered in the
shadows of the walls long after the main trunk glacier had receded
beyond the head of the valley.

Had the glaciers that once covered the range been melted at once,
leaving the entire surface bare from top to bottom simultaneously, then
of course all the lakes would have come into existence at the same time,
and the highest, other circumstances being equal, would, as we have
seen, be the first to vanish. But because they melted gradually from the
foot of the range upward, the lower lakes were the first to see the
light and the first to be obliterated. Therefore, instead of finding the
lakes of the present day at the foot of the range, we find them at the
top. Most of the lower lakes vanished thousands of years before those
now brightening the alpine landscapes were born. And in general, owing
to the deliberation of the upward retreat of the glaciers, the lowest of
the existing lakes are also the oldest, a gradual transition being
apparent throughout the entire belt, from the older, forested,
meadow-rimmed and contracted forms all the way up to those that are new
born, lying bare and meadowless among the highest peaks.

[Illustration: THE DEATH OF A LAKE.]

A few small lakes unfortunately situated are extinguished suddenly by a
single swoop of an avalanche, carrying down immense numbers of trees,
together with the soil they were growing upon. Others are obliterated by
land-slips, earthquake taluses, etc., but these lake-deaths compared
with those resulting from the deliberate and incessant deposition of
sediments, may be termed accidental. Their fate is like that of trees
struck by lightning.

The lake-line is of course still rising, its present elevation being
about 8000 feet above sea