356 



W. T. BRIGHAM ON THE VOLCANIC PHENOMENA 



Fig. 9. 



Plan of the Makapiiu 

 Ridges. 



bad met here. The soil is in many places quite red from the oxide of iron, and the water 

 in the pools is often coated with the iridescent film of the hydrated peroxide. 



In the valley of Palolo the decomposed lava has formed a stiff, tenacious, light-colored clay 

 which constitutes so large a proportion of the soil as to give the valley its name. Towards 

 the east the valleys are small, destitute of running streams, and the ridges point inward as 

 in the figure. Caves are more frequent near this end of the island, 

 and some are of considerable extent. The soil is red, dry and covered 

 with loose stones. In ancient times this barren land was cultivated, 

 and the small piles of loose stones show where the sweet-potatoes were 

 planted, the stones retaining moisture, and serving as supports. At 

 present, wild cotton (Gossypium tomentosurn), a few Convobulacece, sidas, 

 and argemones constitute the vegetation during the summer. There 

 are no trees, save a few Nawiliwili (Erythrina monosperma). 



The mountain ends abruptly at Makapuu, and the only pathway leads over an almost 

 perpendicular precipice nearly eight hundred feet high. From this the whole aspect of the 

 island changes. The deep valleys like Nuuanu and Manoa, and the sterile rock-paved region 

 of Koko, have alike disappeared, and a narrow strip of bright green land extends for eight 

 or ten miles, bounded on one hand by the green ocean, and on the other by an almost 

 unbroken wall nearly two thousand feet high. A section through the island here at right 

 angles to the main ridge would be approximately represented by the annexed diagram. 



The summit is a very sharp edge 

 through which many holes are visible 

 from beneath, and the base is covered 

 with fallen rocks and earth so as to 

 furnish a pathway for the goats to 

 the top. 



The reef has been raised nearly twenty feet at this point, and the whole coast is fringed 

 with a reef now growing and extending out in some places four thousand feet. From this 

 reef the sand is washed in, forming dunes thirty feet high in some places, of a dazzling 



whiteness. There are several 



small islands off the 



dently the remains of tufa cones ; 



the largest is represented in the 



Fig. 10. Section of Konahuaniii from North to South, 

 a, a, compact basalt ; b, debris from the cliffs ; c, dunes of coral sand. 



shore, evi- 



a - figure. 



The pali of Koolaii is one of the 

 most remarkable formations on 

 Oahu, and the interest with which 



Fig. 11. Island Crater off the northern coast of Oahu. [^ Jg regarded by geologists is 



much increased by the explanation Prof. Dana gives of its origin. 1 It must not be inferred 

 from that explanation that this wall is a clear unbroken perpendicular precipice of regular 

 curve. Whatever may have been its condition a quarter of a century since, at present 

 there is a considerable talus at the base, composed of fragments of rock intermingled with 

 the earth washed from above. It is quite difficult to ascertain the dip of the exposed strata, 

 as the cliffs are quite inaccessible. From below they certainly seem to dip towards the 



l Loc. cit. p. 258. 



