ierras, where the gold is
found, have been made by the American and Feather rivers. Farther
south are the deeper and more rugged canons of the Tuolumne, Merced,
King's, and Kern rivers, which open to us inviting pathways into
the mountains.

It might be supposed that the mantle of snow and ice which at that
time covered most of the surface of the earth would have protected
it from further erosion, but this was not the case. In the basin
at the head of each stream the snow accumulated year after year
until it was more than a thousand feet deep. Under the influence
of the warm days and cold nights the snow slowly turned to ice,
and moved by its own weight, crept down into the canons. The solid
rock walls were ground and polished, and even now, so long a time
after the glaciers have melted, some of these polished surfaces
still glisten in the sunlight. The glaciers deepened and enlarged
the canons, but running water was the most important agent in their
making.

Upon the disappearance of the glaciers, the streams went to work
again deepening their canons. From their starting-points, under
the lofty crags, they first ran through broad upland valleys, then
tumbled into the canons; but until they had reached the lower mountain
slopes, to which the glaciers had not extended, they passed through
a dreary and desolate region devoid of almost every sign of life.
The glaciers had swept away all the loose rock and soil, and it was
many long years before the surface again crumbled so that forest
trees could spread over it once more.

The grandeur and attractiveness of the Yosemite is partly due to
the precipitous cliffs enclosing the valley, some of which are
nearly four thousand feet in height, partly to the high waterfalls,
and partly to the green meadows and forest groves through which
the Merced River winds.

Although the glaciers had little to do with the making of the Yosemite
Valley, yet they added to its attractiveness. The valley is situated
where a number of smaller streams join the Merced River. Erosion was
more rapid here because the granite was soft, while the vertical
seams in the rock gave the growing valley precipitous walls. When
the glacier came it pushed out the loose rocks and boulders, and
dropping a portion of them at the lower end, made a dam across
the Merced River. At first a shallow lake filled the valley, but
after a time the silt and gravel which the streams were continually
bringing in filled the