erroneous.

The decrease in rain and snowfall since the close of the glacial period
in the Sierra is much less than is commonly guessed. The highest
post-glacial water-marks are well preserved in all the upper river
channels, and they are not greatly higher than the spring flood-marks
of the present; showing conclusively that no extraordinary decrease
has taken place in the volume of the upper tributaries of post-glacial
Sierra streams since they came into existence. But, in the meantime,
eliminating all this complicated question of climatic change, the plain
fact remains that the present rain and snowfall is abundantly sufficient
for the luxuriant growth of sequoia forests. Indeed, all my observations
tend to show that in a prolonged drought the sugar pines and firs would
perish before the sequoia, not alone because of the greater longevity of
individual trees, but because the species can endure more drought, and
make the most of whatever moisture falls.

Again, if the restriction and irregular distribution of the species be
interpreted as a result of the desiccation of the Range, then instead of
increasing as it does in individuals toward the south where the rainfall
is less, it should diminish. If, then, the peculiar distribution of
sequoia has not been governed by superior conditions of soil as to
fertility or moisture, by what has it been governed?

In the course of my studies I observed that the northern groves, the
only ones I was at first acquainted with, were located on just those
portions of the general forest soil-belt that were first laid bare
toward the close of the glacial period when the ice-sheet began to break
up into individual glaciers. And while searching the wide basin of the
San Joaquin, and trying to account for the absence of sequoia where
every condition seemed favorable for its growth, it occurred to me that
this remarkable gap in the sequoia belt fifty miles wide is located
exactly in the basin of the vast, ancient mer de glace of the San
Joaquin and Kings River basins which poured its frozen floods to the
plain through this gap as its channel. I then perceived that the next
great gap in the belt to the northward, forty miles wide, extending
between the Calaveras and Tuolumne groves, occurs in the basin of the
great ancient mer de glace of the Tuolumne and Stanislaus basins; and
that the smaller gap between the Merced and Mariposa groves occurs in
the basin of the smaller glacier of the Mer