232 • CALIFORNIA ACADEMY OF SCIENCES. 



sides of former lava currents, that is to say the slope has been 

 rendered uneven by these small flows, and as their surfaces dis- 

 integrated they also became covered with debris, while the sides 

 subjected not less perhaps to the wasting effects of decomposition 

 are the only portions where the massive rock is still visible as 

 the products of decomposition were unable to collect on their 

 surfaces. The slopes gradually become more even as they ex- 

 tend around to the western side of the mountain. Lower down 

 on the northerly and easterly sides of the mountain, among the 

 timber, the remains of larger flows are very frequent, sections as 

 it were of great lava currents, the upper and lower portions of 

 which have wholly disappeared. These are for the most part 

 but piles of bowlders, though in several instances the scoriaceous 

 surface of the bottom of the bed was still distinguishable. 



On the west side of the mountain about two thousand feet be- 

 low the summit, is a black dome-shaped cone, very regular in 

 form and some two hundred feet in height. Its steep sides are 

 entirely composed of huge irregular shaped blocks of rock, 

 whose sides and edges are as fresh and sharp as though but 

 freshly hewn from a quarry. No finer material or sand is ob- 

 servable between these large blocks; there is no depression on 

 the top, nor any sign of any lava current having flowed from its 

 immediate neighborhood — in fact, none of the characteristics of 

 the parasitic cone, composed of scorias and tuff, and generally 

 marking the external source of a lava stream, which is so fre- 

 quently found studding the flanks and base of large volcanoes. 

 Twenty-five degrees further south and some three hundred feet 

 higher up on the side of the mountain, is another cone the exact 

 counterpart of the first in height, form and structure. These 

 cones stand to-day just as they were originally formed; there is 

 no sign of weathering of the rock or other change due to exter- 

 nal influences. A modern instance of the formation of a vol- 

 canic cone comjjosed of viscous lava, its surface, at the time of 

 its formation, consisting of loose blocks of rock, has been ob- 

 served and described in Mt. Giorgios at Santorin, by Messrs. 

 Reiss and Stiibel in their " G-eschichte und Beschreibung der 

 Vulkanischen Ausbriiche bei Santorin." This fragmentary 

 character of the rock is also noticeable on the summit of Mt. 



