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 occured to me that
this remarkable gap in the Sequoia belt is located exactly in the basin
of the vast ancient _mer de glace_ of the San Joaquin and King's
River basins, which poured its frozen floods to the plain, fed by the
snows that fell on more than fifty miles of the summit. 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 Merced.
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