1872.] Al [Kneeland. 
to form a soil thick enough for the general growth seen in the valley 
itself. Wherever, says Mr. Muir, a deep tributary was laid against a 
narrow ridge, sheltered from the sun by surrounding rocks, there are 
invariably found one or more small terminal moraines; melted off 
from the main trunk, with an independent and longer duration, their 
moraines are left entire, because the water basins above them do not 
furnish streams large enough to wash them away, as is the case in 
the moraines of the cafions and deeper water courses. In the basins 
of exposed tributaries there are no terminal moraines, as their gla- 
ciers disappeared with the main stream. He says “ Medial and lat- 
eral moraines are common upon all the outside slopes, some of them 
nearly perfect in form; but down in the main basin there is not left 
one unaltered moraine of any kind, immense floods having washed 
down and levelled them into border meadows for the present stream, 
and into sandy flower beds and fields for forests.” 
Between the three upper tributaries of the Yosemite basin glacier, 
he found well defined medial moraines, these having been preserved 
from levelling floods by their position on the higher slopes, with only 
small water collections behind them. Down at their junction, where 
they were swept round by the main stream, is a large level field of 
moraine matter, which, like all the drift fields of this basin, is covered 
with a dense forest, principally the Pinus contorta and Picea amabilis, 
the summit forests being composed almost entirely. of this thickly- 
growing and pitch-covered pine. ‘The domes of this upper basin pre- 
sent the same concentric structure and perpendicular cleavage already 
alluded to in the North and the Half-Dome of the Valley. Next west 
of the Yosemite basin, on the north side of the valley, is the Ribbon 
stream basin, in which now runs the stream flowing into the valley 
west of El Capitan by the Virgin’s Tears fall, dried up so early in the 
summer that it is rarely seen by travellers. This basin Mr. Muir 
found was occupied by a glacier, flowing nearly south, about four miles 
long, and three wide, jeining the central glacier, west of El Capitan. 
He spent two days in this basin, whose glacier was one of the small- 
est which entered the valley, the most of whose ice was derived from 
a south-west spur of the Hoffman group. The slope of its bed is 
steep and regular, and its ice must have moved with considerable ve- 
locity; exposed to the southern sun, it must have disappeared among 
the first, leaving a comparatively long period for the obliteration of 
the striated surfaces by the storms and the various disintegrating 
agencies of the weather ; as in the Yosemite basin, the unprotected 
