ANCIENT SANDSTONE, SHALE AND CONGLOMERATE. 639 
tinguished. In the bluffs, the sandstone is divided into distinct layers 
of deposition, of varying thickness, from a few inches to several feet. 
These layers are very irregularly fissured or cracked, and break into 
wedge-shape and rhombic fragments. ‘Some of the layers are imper- 
fectly schistose, and others pass into a slate rock, which splits easily 
into thin plates. The latter resembles the talcose argillite already de- 
scribed; but the laminz are less smooth and shining, and moreover, 
the rock contains the same glistening scales as the sandstone. 
The puddingstone of the Shasty Mountains is a very hard, compact 
rock, composed of pebbles of quartz, flint, jasper, and others from the 
talcose and prasoid rocks. ‘The pebbles are often smoothly polished, 
and of various fancy colours: black, red, rose-red, green, and gray of 
various shades are the more common tints. Coarser conglomerates 
contain rounded stones five or six inches in diameter. 
The puddingstone of the Umpqua is very similar to the rock just 
described. ‘The pebbles averaged half an inch in diameter, and were 
mostly quartzose, some of them like flint. 
A conglomerate and shale, the latter resembling somewhat the rock 
of the Shasty Mountains, occur near the Bay of San Francisco, and 
probably pertain to this formation. I observed them on the shores of 
the harbour of Sansalito. 
These rocks give very rough features to the landscape, resembling 
much the features of the talcose regions. On Destruction River, 
deep holes, roughened with points, had been eroded by the action of 
the stream on this rock, and jagged ridgelets and miniature peaks 
were left standing along the shores. Where the puddingstone pre- 
vailed, the country was covered with pebbles, and the soil was nearly 
as unproductive as the bare sides of the rock itself. 
The slate appears to be the lower member of the series in the 
Shasty Mountains, and the puddingstone the upper. The latter 
occurs in thick deposits between layers of the compact and schistose 
sandstone, and also constitutes steep ridges seven or eight hundred feet 
high. Numerous veins and seams of quartz intersect the rock as in 
the members of the talcose series. 
The dip and strike of the layers are constantly changing, and show 
that there have been great displacements and contortions. The angle 
of dip is commonly between thirty and sixty degrees; yet it varies 
from thirty degrees to verticality often within a distance of twenty 
yards. The layers are sometimes twisted around and folded over on 
themselves. The general direction is north and south, though there 
