Geol.— Vol. I.] SMITH—SANTA CATALINA ISLAND. 43 



2. Tuff. 



The tufaceous beds are not wholly of volcanic material, 

 but contain more or less of the shale fragments, besides 

 having occasionally a matrix of the shale (diatomaceous 

 earth). They also contain fragments of the metamorphic 

 material similar to that composing the underlying basement 

 rocks. The rock as a whole is rather soft, and usually 

 somewhat compact. One of the highest beds is made up 

 of moderately fine angular material and is somewhat porous, 

 as it has very little cementing material. Usually fragmental 

 shaly material appears to form most of the finer portion of 

 the rock. Some of the beds are more or less even-grained, 

 composed wholly of moderately fine material, and contain- 

 ing nothing larger than half an inch in diameter. Others 

 contain, besides this, large angular blocks, the largest attain- 

 ing a length of about two and a half feet, though most of 

 them are less than a foot and a half in length. By the 

 weathering of the face of the cliffs many of these blocks 

 project from the surface. In this way both the larger and 

 smaller fragments gradually work out and fall to the base of 

 the cliff. These blocks are composed almost wholly of 

 very vesicular and usually much reddened, andesitic lava. 

 A few large fragments of shale were seen in these coarser 

 beds and a number of angular blocks of the metamorphic 

 material, some of them a foot and a half in length. These 

 beds, are in places fossiliferous, and it is said that large 

 pectens have been found in them. No fossils were found 

 by the writer, however. 



3. Shale. 



The shale wherever found is white or light gray in color, 

 but it varies considerably in texture and composition. As a 

 rule the rock is very soft and earthy, and can be easily 

 scratched with the nail. In this condition it has a low 

 specific gravity. The more earthy and less compact the 

 rock, the more easily it splits into thin sheets. The lightest 



