388 Prof. Blake on the Diluvial Deposits in California. 
other points, the clay is entirely absent, and the whole series con- 
sists of beds of conglomerates and soft friable sandstone. In the 
the trap and quartz, they generally fall to pieces on exposure to 
the air. The strata as before observed are nearly horizontal and 
conformable ; if they have any dip, it appears to have been owing 
to the slope of the surface of the rock on which they were de- 
posited ; in fact no displacement seems to have taken place in 
the country since the period of their formation. »They lie per- 
fectly horizontal over the almost vertical edges of the upheaved 
slate rocks. - : ef i 
_» Pieces of half carbonized wood, and impressions of leaves are 
sometimes found in the clayey beds of these deposits, and at 
Nevada it is’ said that the trunk of a tree had been. traced for 
some distance in the clay, at about forty feet. below the surface. 
I have obtained specimens of wood and also imperfect impressions 
of leaves taken out four or five hundred feet below the surface 
the ground, and three hundred and fifty feet from the side of 
the hill,.at.the same locality. The wood. belongs to one of the 
Coniferee, but L was unable to determine the character of the 
leaves. A tooth also has been found in some of these deposits. 
I have not seen it, but from description it would appear to be a 
bicuspid belonging to some large Pach yderm. The surface of the 
rock on which they repose, generally presents evidence of con- 
siderable abrasion, but L have been unable to detect. any regular 
grooves in it. Where it is more elevated it has been less worn, 
some of the edges of the slates being not much broken. AS Te 
gards their age there can be but little doubt that they belong 
to a comparatively recent period. ‘They were evidently formed 
subsequently to the convulsions which upheaved the older strati- 
fied rocks and in fact there appears to be no evidence of any & 
ological disturbance since their deposition except in the simulta- 
