302 CALIFORNIA ACADEMY OF SCIENCES. 



may not affect the main question of their original con- 

 tinuity. 



As previously stated, the best section observed was that 

 running from Pescadero Point almost to Pigeon Point. 

 (Plate xxiv) . The strata are almost perpendicular for the 

 v/hole distance of over five miles ; at the northern end 

 disappearing under some gently dipping strata, and at the 

 southern end, where the dip of the beds becomes lower, 

 being cut off by a fault. The section was made by pacing 

 and abundant observations upon the dip and strike, cor- 

 rected by the U. S. Coast and Geodetic Survey chart of 

 that region. The section was not examined in great de- 

 tail, and the frequently varying strike gave room for the 

 presence of faults; but though carefully watched for, 

 none were found of any magnitude except the one at the 

 south end of the section. The section gave a thickness 

 of nearly ii,ooo feet, composed, with the exception of 

 600 feet of conglomerate at the southern end, of the 

 thin bedded and heavy bedded sandstone, changing rapid- 

 ly from one to the other all through the section. The 

 predominating layers average from three inches to a foot 

 in thickness. Over a large part of the exposure the dip 

 is as high as 85°, but near the southern end quickly be- 

 comes lower, at the fault being only about 30°. South of 

 the fault the dip is still lower, becoming nearly horizontal 

 just north of Pigeon Point. 



One question of vital importance remains undecided. 

 That is, which is the bottom and which is the top of the 

 section? Other things being equal it would generally be 

 assumed that the conglomerate was at the bottom of the 

 series. But the low dips at the south end of the section 

 point to the conglomerate as the uppermost member. If 

 the conglomerate is the lowest member then the whole 



