GEOL. VOL. I.] SMITH SANTA CAT A LIN A ISLAND. 31 



between this point and Whitley's Cove the bands are more 

 or less irregularly flexed, though preserving a general par- 

 allelism to the shore-line. 



Another small area of these rocks is found along the coast 

 to the east of Empire Landing. 



The area of andesite near the isthmus is also formed by a 

 series of flows which show a distinct banding along the cliff 

 on the ocean side. This banding preserves a course rough- 

 ly parallel to the water-line till near Isthmus Cove, where it 

 changes its direction, dipping at an angle of about 25 to- 

 ward the point at the entrance to the cove, as shown in the 

 section on the map. This formation reaches its greatest 

 altitude near the southeastern end, where it is about 900 

 feet above sea-level. Along the northern shore-line of this 

 area adjoining Isthmus Cove numerous faults are seen (not 

 shown on the map), ranging in throw from a few inches 

 to a hundred feet or more. 



The most marked feature of this area is a distinct white 

 band following the upper line of the cliff for some distance, 

 and overlying the volcanic rocks. This is the bed of tuff 

 and diatomaceous earth already mentioned as occurring with 

 the volcanics here. That the andesite lies above as well as 

 below it is plainly seen at a number of points. An espe- 

 cially good section showing the upper contact of the tuff is 

 obtained in the little bay to the east of Isthmus Cove. Here 

 the tuff is overlain by porous andesitic rocks. 



The rocks along this part of the shore have been hollowed 

 out in places by the force of the waves, forming caves, pil- 

 lars, and blow-holes. 



The coarse banding of the andesites along the cliff sec- 

 tions shows a variety of colors, the rocks weathering in dark 

 grayish or purplish with occasional reddish tints. The soil 

 formed by this series of rocks is always purplish in color, 

 and is easily distinguished, even at a distance, from the soils 

 which the other rocks of the island form, the latter being 

 either reddish or yellowish. 



Macroscopic Characters. The freshest specimens of the 

 andesite are black or nearly so. Though the rocks are in gen- 



