Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

GEOLOGY.
the summits in broad, white fields that glistened under the rays of an unclouded sun, and by
its rapid melting kept the rivers well supplied with water.
The crest of the chain, nearly east from the ferry, has a very peculiar appearance, and seems
to be divided into a succession of tranverse ridges, standing sharply out at right angles to the
general direction of the chain, giving it an outline like the teeth of a saw.
_
_._ _ _
S_ OF _ _= == =EVAA, F_. R S =_
-, ~ -~ ~.
CREST' OF THE SIERRA I.'EYADA, FROM KING S RIVER.
Three principal ridges of this character were easily seen by the naked eye, but with a glass
many more were observed. They were evidently the outcropping edges of rocks dipping towards the south at angles of seventy to eighty degrees. Their outlines were deeply serrated;
and this appeared to be the result of the breaking or gapping out of their sharp edges, either
by abrasion, or, more probably, by the undermining action of the weather, permitting portions of the rocks to fall by their own weight. The nearly level spaces between these singular
ridges were covered with snow, but no snow could be observed on the abrupt and precipitous
slopes of the rocks. It is possible that the valleys are occupied by glaciers.
The distinctness with which these serrated rocks are visible at the distance of probably over
fifty miles, and at an elevation of over seven or eight thousand feet, shows that they have a
great elevation above the general surface of the ridge. A similar structure is developed along
the crest of the chain for several miles towards the south. I was surprised to find such an extended series of outcrops with their trend apparently at right angles to the general direction of
the chain on which they occur. From the character of their edges and the tabular appearance
of their surfaces, I concluded that they were slate rocks-probably metamorphic or azoic.
From King's river to the Four Creeks the surface of the ground shows but few undulations,
and may be considered as nearly level. The soil contains a large portion of clay, and must
necessarily become soft and miry during the rainy season. About three miles northward of
Elbow creek, (one of the "Four Creeks,") a large area of surface is coml E,d almost wholly of
clay, without any admixture of sand or gravel, and has evidently been nea - fluid in the wet
season. This was shown by the deep tracks of animals in the then hard, su' kedsurface,
and by great numbers of skeletons of cattle that have sunk in the deep, thick mud, and been
left to die of starvation. Their whitened bones stand upright in the clay like pos.s around a
grave. The drying up of this clayey ground has produced deep shrinkage cracks and fissures,
similar to those observed in the rich soils around the bay of San Francisco.
Four Creeks.-From the level of the arid and treeless plain, bounded on the west in the dim
distance by equally barren mountains, we made a sudden descent of about ten feet to the bot
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