ns, their fragmentary condition being due to interruptions
caused by portions of the sides of the canyon walls being too steep for
moraine matter to lie on, and to down-sweeping torrents and avalanches.
The left lateral of the trunk may be traced about five miles from the
mouth of the first main tributary to the Illilouette Canyon. The
corresponding section of the right lateral, extending from Cathedral
tributary to the Half Dome, is more complete because of the more
favorable character of the north side of the canyon. A short
side-glacier came in against it from the slopes of Clouds' Rest; but
being fully exposed to the sun, it was melted long before the main
trunk, allowing the latter to deposit this portion of its moraine
undisturbed. Some conception of the size and appearance of this fine
moraine may be gained by following the Clouds' Rest trail from Yosemite,
which crosses it obliquely and conducts past several sections made by
streams. Slate boulders may be seen that must have come from the Lyell
group, twelve miles distant. But the bulk of the moraine is composed
of porphyritic granite derived from Feldspar and Cathedral Valleys.

On the sides of the moraines we find a series of terraces, indicating
fluctuations in the level of the glacier, caused by variations of
snow-fall, temperature, etc., showing that the climate of the glacial
period was diversified by cycles of milder or stormier seasons similar
to those of post-glacial time.

After the depth of the main trunk diminished to about five hundred feet,
the greater portion became torpid, as is shown by the moraines, and
lay dying in its crooked channel like a wounded snake, maintaining for
a time a feeble squirming motion in places of exceptional depth, or
where the bottom of the canyon was more steeply inclined. The numerous
fountain-wombs, however, continued fruitful long after the trunk had
vanished, giving rise to an imposing array of short residual glaciers,
extending around the rim of the general basin a distance of nearly
twenty-four miles. Most of these have but recently succumbed to the new
climate, dying in turn as determined by elevation, size, and exposure,
leaving only a few feeble survivors beneath the coolest shadows, which
are now slowly completing the sculpture of one of the noblest of the
Yosemite basins.

The comparatively shallow glacier that at this time filled the
Illilouette Basin, though once far from shallow, more resembled a lake
th