SANDSTONE AND CONGLOMERATE—ROUNDED HILLS. 
9 
A stratum of conglomerate forms a prominent feature of the rocks of Livermore’s pass. It 
appears at intervals in the form of huge outliers, apparently unconnected with any substratum 
of rock. It is similar to that observed at Benicia, and is probably a continuation of the same 
bed. A westerly dip of about 20° was observed at one of its outcrops. One of these outlying 
masses is composed chiefly of pebbles, of the size of beans or peas, but firmly cemented together, 
so that masses could be broken off by the hammer. At other places large stones and pebbles 
were seen. At one of the principal outcrops of this character the upper part of the mass is a 
thick bed of compact sandstone, and under it a second bed enclosing pebbles of quartz and a 
large round fragment of compact, fine-grained limestone, resembling that used by lithographers. 
The sandstone above also contains round masses harder than the rest of the rock, but probably 
concretionary. They do not weather as rapidly as the surrounding rock, and stand out from it 
in relief. The foundation on which the layer of sandstone rests appears to wear away most 
rapidly, and the rock is thus left projecting above, and far enough to afford the traveller pro¬ 
tection from the weather, the height of the whole being about thirty feet. At the base of this 
curious rock there are several cylindrical or conical cavities in the stone, about six inches in 
diameter and eight to ten deep. They are perfectly smooth at the sides and bottom, and were 
probably formed by the Indians for pounding their barley. 
About a mile east of the summit an outcrop of sandstone in the side of one of the hills con¬ 
tained numerous globular or spherical masses of sandstone, two or three feet in diameter. They 
are harder than the surrounding portions, and appeared to be the result of concretionary action 
rather than to be due to the decomposition of angular blocks. A small outlier of this descrip¬ 
tion is represented in the figure. 
CONCRETION AND ARCH OF SANDSTONE. 
The sandstone adjoining the spheroidal mass has worn away so as to leave an arch, so perfect 
as to appear to be the work of art rather than the result of decay. 
Outerops of the strata became more common on the eastern side of the pass, and were of 
greater extent, but not so high and imposing. One of the exposures consisted of a bed of sand¬ 
stone, weathered into fanciful forms—columns, spires, and sharp points. It is underlaid by a 
coarse conglomerate, and the pebbles which have been loosened from it cover the surrounding 
surface. 
The slopes of the hills on the eastern side of the range are more gradual and gentle than on 
the west; this is also the case with the dips of the strata, which vary from ten to twenty 
degrees. 
"While the surveying party were measuring the pass, and taking barometrical observations, 
I travelled up one of the side ravines towards the north, and found everywhere the same charac¬ 
teristic steep, but rounded, hills and barren surfaces. 
This barrenness, however, was only apparent. The season of green grass and flowers had 
passed, and fires had swept over the region, burning all the straw of the wild-oat and the stalks 
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