This impalpably fine sediment was deposited quietly and uniformly over 
the uneven, pebbly surface of the conglomerate; and consequently where 
erosion has cut down nearly to the top of the conglomerate, each pebble 
determines the center of a series of concentric lines, the outcropping 
edges of the laminae of slate. In the portion of the eroded surface here 
represented, the banded slate has been worn away sufficiently to actually 
expose only two pebbles of the conglomerate. 
In the upper part of this thin bed of tuff, where it experienced more dis- 
tinctly the mechanical stresses of the overflowing lava, the layers are, 
to some extent, finely brecciated and faulted, as shown in the illustrations 
on the next plate. 
