COAST RECORDS OF THE RISE OR FALL OF LAND 257 



and Fig. 278, p. 250). Midway between these two rising sections 

 of the crust, and less than twenty-five miles distant from either, is 

 the island of Santa Catalina, which has been sinking beneath the 

 waves, and apparently at a similarly rapid rate (Fig. 288). The 



FIG. 288. Map of Santa Catalina Island, California, showing the characteristic 

 surface of an area which has long been above the waves, and the entire absence of 

 coast terraces (after U. S. C. and G. S.). 



topography of the island shows the intricate detail of a maturely 

 eroded surface, while that of the neighboring San Clemente shows 

 only the widely spaced, deep canons of the infantile stage of erosion 

 (Fig. 165 and pi. 12 A). While Santa Catalina has been sinking, 

 San Pedro Hill has risen 1240 feet, and San Clemente, 1500 feet. 

 It is characteristic of a sinking coast line that the cliff recession is 

 abnormally rapid, and evidence for this is furnished by the shores 

 of Santa Catalina, upon which the waves are cutting the cliffs 

 back into the beds of canons, and so causing small falls to develop 

 at the canon mouths. 



The Blue Grotto of Capri. We may now return to the Bay 

 of Naples for additional evidence that oscillations of level in 

 neighboring portions of the same coast are not necessarily syn- 

 chronous, and that near-lying sections may even move in opposite 

 directions at the same time, as has already been shown for the isl- 

 ands off the California coast. For the Pozzuoli shore of the bay 

 it was learned that within the Christian Era a complete cycle of 

 downward, followed by later upward, movement has been largely 

 accomplished. Across the bay, and less than 20 miles distant, is 

 the Blue Grotto of Capri, a sea cave cut in limestone above an 

 earlier cave of the same nature which is now deep below the water 

 surface. It is the refracted sunlight which enters the cave through 



