7 6 



University of California. 



[Vol. i. 



spheroidal basalt and the diabase to the east, is seen to rise from 

 the water's edge, pass immediately to the right of the natural bridge, 

 and run up to the top of the cliff at a point a little west of the light- 

 house. The line is quite sharp, and the difference of character in 

 the two rocks, thus placed in juxtaposition, very striking; but the 

 sea and weather have transformed the junction into a more or less 

 open cleft, and it is impossible to say whether it is a line of faulting, 

 or a true igneous contact. A few steps to the east, spheroidal 

 basalt again occurs, and at the southeast extremity of the point 

 may be seen a structure less striking, but similar to that just de- 

 scribed. 



Leading from the fog siren to the keeper's house, a path has 

 been cut in the rock, and affords opportunity for examining the 

 structure of the point on the east side. Just behind the store shed 

 at the head of the landing stairs, the cutting exposes the sectional 

 forms shown in Fig. I. The sections are traversed by a number of 



Figure i. — Section of spheroids beside the path, near storehouse of the fog 

 signal station. 



cracks, it being generally possible to discern something like regu- 

 larity in the way in which those transverse to .the longer axes of 



