Geol.— Vol. I.] SMITH— SANTA CATALINA ISLAND. 53 



fragments of andesite seen near the upper part of the series. 

 The bedding of the breccia is seen on the upper part of the 

 chffs at the northern end of the area as a rather coarse 

 banding, approximately parallel to the shore-line. Toward 

 the south the banding becomes somewhat irregular and is 

 lost to view some time before the extreme point is reached. 

 Here the breccia is seen at the base of the cliffs, and so far 

 as could be determined it is, in part at least, included in the 

 porphyrite (see Plate III, fig, i) which occurs here on the 

 cliffs just above. 



This porphyrite is a white, much weathered rock, and it 

 is possible that it occurs here as a dike of considerable size, 

 or as an intrusive sheet, and does not belong to the main 

 occurrence of this rock. At any rate it is in some respects 

 unlike the porphyrite as it usually occurs. Within the area 

 just described the porphyrite outcrops along the shore at one 

 other point, at least, where the rock is to all appearances 

 like that of the main area. The breccia at the point of the 

 island is cut by a dike of greenish porphyrite about two 

 feet wide, which also cuts the white porphyrite mentioned 

 above. 



About midway between Pebbly Beach and the extremity 

 of the island there is a small beach at the base of the cliffs, 

 which is partly made up of boulders and smaller masses of 

 a conglomerate resembling the breccia in the material of 

 which it is composed. This has apparently fallen from the 

 cliffs above, although no rounded material was anywhere 

 seen in place by the writer. So far as observed, these 

 boulders are composed of water-worn metamorphic pebbles, 

 imbedded in a large amount of compact, greenish cement. 

 This cement shows a marked effervescence with dilute acid, 

 and under the microscope it is seen to be composed in large 

 part of angular fragments of quartz and quartzite, in a thin 

 cement which is largely calcite. Several small sections 

 were seen, closely resembling the porphyrite in appearance, 

 and containing porphyritic feldspars, but much altered by 

 decomposition products. 



The observations made were too limited to prove conclu- 



