;™h] The Berkeley Hills. 385 



zone of beetling crags and walk over a .smooth sward, where no 

 rocks are visible. It is true, the terrace is not more than four or 

 five hundred feet wide, but its striking contrast with the steep, rocky 

 slopes below and above it challenges our attention; it requires but 

 a moment's reflection to convince us that we are upon a soft forma- 

 tion that has succumbed to the forces of degradation to which the 

 hard rocks on either hand are still boldly resistant. 



Character of Beds. — This conviction is readily verified by a 

 little investigation as to the character of the underlying formation. 

 Observation on this point is possible at the head of the ravines 

 which notch the face of Frowning Ridge escarpment, and at other 

 places. In the middle of the terrace we meet with a pit or shaft 

 which has been sunk in the work of tapping the water which is 

 contained in the water-bearing strata of the hills. Around the 

 mouth of the pit is a dump of the material which was taken from 

 it. This dump consists chiefly of a light gray very friable sand- 

 stone with a subordinate amount of clay. In this sandstone have 

 been found fresh -water fossils. 



In the water course which drains down to the next ravine to 

 the south into Telegraph Canon we find exposures of blue clay and 

 numerous fragments of a yellowish chert, such as is commonly 

 found in other parts of the hills associated with fossiliferous fresh- 

 water limestone. In the same water course, close to the contact with 

 the upper surface of the andesite, there is an exposure of distinctly- 

 stratified, peaty shales, dipping to the northeast at high angles. 

 A little farther to the south, in the water course draining to Siesta 

 Valley, we find excellent exposures of clay-shales with thin seams 

 of lustrous black lignite. The stratification is well marked, and the 

 direction of dip is the same as before, but at much lower angles. 

 Farther down the same water course light blue clays are abundantly 

 exposed. The evidence of repeated landsliding, which marks this 

 end of Siesta Valley, suggests that this clay formation underlies 

 the surface extensively. In addition to these various indications of 

 the character of the underlying formation, we find along the base 

 of the formation, close to the upper surface of the andesite, out- 

 crops of a thin bed of limestone of a very light gray color and 

 compact texture. The exposures are not abundant, and they are 



