Smith.] 



Islands of Southern California. 



2 I I 



distance CB of, roughly, 675 feet will have been cut in the other 

 slope. 



If, at this point, an elevation of 100 feet occurs (indicated by 

 the new sea level D'E' — DE), the shore line, for the gentler slope, 

 will be shifted from B' to D', a horizontal distance of 2,500 feet 

 (B'C'= 1,500 feet, and D'F'= 1,000 feet, for the angle assumed). 

 The shore line of the steeper slope will be transferred from B to D, 

 a horizontal distance of about 875 feet (CB = about 675 feet, DF = 

 200 feet, for the angle assumed). 



As before, the waves will be somewhat longer in making a 

 start at D than at D', on account of the steeper off-shore slope, 

 but this difference in the beginning of the destruction of the two 

 terraces, C'B' and CB, will be practically offset by the corre- 

 sponding difference at the beginning of their construction, when the 

 sea made its first attack at C and C. 



Since DF is smaller than D'F r (the ratio being one to five in 

 the example under consideration), and since the altitudes F'C and 

 FC are approximately the same, the volume to be removed in 

 cutting back from D to F is less than that to be removed in cutting 

 back from D' to F' (roughly one-fifth, in the present case) ; so that 

 the point F will have been reached by the waves before the point 

 F' has been reached. After the waves have cut back in both 

 cases to the terrace platforms, CB' and CB, the further cutting 

 will be at approximately the same rate for both, since the cliffs now 

 have equal altitudes (about IOO feet above sea-level),* and other 

 conditions are the same in the two cases, except that there will be 

 a greater width of submarine platform to be worn down in con- 

 nection with the cliff cutting in the obliteration of the terrace 

 formed on the gentler slope than in the case of the steeper slope. 

 This will offset the corresponding difference in the formation of 

 the terraces. 



* These first platforms were not level from front to rear, but had a seaward 

 inclination, owing to the abrasion of the platform surface off-shore; so that 

 alter elevation the height of the cliffs is less than 100 feet above sea-level, on 

 the average. This is offset, however, by the fact that in the cutting at the 

 second level the second platform must be worn down by a corresponding 

 amount. 



