Lawson.] 



Post- Pliocene Diastrophism . 



135 



knew the rate of recession of the cliffs, we might from this data 

 acquire a minimum value for the time occupied in the uplift. 



In comparing the figures obtained for the altitudes of the ancient 

 strands of San Pedro Mill with those of San Clemente, the interest- 

 ing and suggestive fact comes out that the highest three terraces 

 of the former series have exact hypsometric equivalents in the lat- 

 ter, and that most of the other lower terraces of San Pedro Hill 

 seem also to have their strict equivalents on the island. The sug- 

 gestion is that the hill and the island have emerged from the sea in 

 unison, at the same rate, by the same stages. The facts to be nar- 

 rated concerning Santa Catalina Island tend, however, to discredit 

 this suggestion, as will appear in the sequel. 



SANTA CATALINA ISLAND. 



Compared with San Pedro Hill and San Clemente. — In all the 

 physiographic wonderland of Southern California there is probably 

 nothing more surprising than the contrast which the topography 

 of Santa Catalina presents to that of both San Pedro Hill and San 

 Clemente. Lying midway between the two latter insular masses, 

 in the same physiographic province, and affected by the same cli- 

 matic conditions, Santa Catalina might, a priori, be supposed to differ 

 from these but little in the character of its land sculpture. This 

 supposition proves, however, to be fallacious. The difference 

 between the aspect of the island and that of the two other neighbor- 

 ing insular masses is amazing, and the hypothesis which we are 

 forced to entertain to account for it, is correspondingly startling. 



The island has almost exactly the same length as San Clemente, 

 and has about the same trend. The greatest width is, however, 

 twice that of San Clemente. Its summit is 2,109 feet above the 

 sea, or only 145 feet higher than that of the sister island. The writer 

 had an opportunity of inspecting the topography of the island under 

 unexceptional conditions, while circumnavigating it in a naphtha 

 launch, within easy reach of shore, in calm, clear weather. All parts 

 of the island were thus passed in critical review. Bearing in mind the 

 account which has been given of San Pedro Hill and San Clemente, 

 the following brief statements will suffice to make clear those fea- 



