362 



W. T. BRIGHAM ON THE VOLCANIC PHENOMENA 



seems to have risen to its present height, and, prevented by the superincumbent tufa, re- 

 mains in the branched and ragged form in which it cooled. At the eastern side is a deep 

 break, and another mass of dark basalt of slightly columnar structure. From the appearance 

 of this side it is by no means evident that this break is coeval with the eruption which 

 marked the formation of the cone ; during the rains water collects in the crater, and a 

 stream of some size rushes over the cliff, carrying with it a large quantity of earth and 

 stones, and this agent has enlarged if not originated the ravine whose former contents are 

 spread in a thick layer over the plain east of Honolulu. Two dykes are seen on this side, 

 the one two, and the other ten feet wide. The basalt of these, as of all the masses visible 

 in this cone, contains some chrysolite and minute grains of augite. On the northern 

 side a conglomerate occurs, seemingly due to the ejection of scoriae from the crater. In 

 several places near the base, masses of rock occur imbedded in the tufa, the latter being 

 raised around them precisely as a thick mud would rise around a heavy body dropped 

 into it. 



Near Punahou at the entrance of Manoa Valley, are marks of another crater, and beyond 

 this is much fresh looking basalt. Some disturbance seems to have caused the appearance 

 of the spring which gives the name to the land of Punahou (New Spring), and which evi- 

 dently flows over extensive lime deposits, probably coral beds, the water being very hard. 

 , v _ Six miles west of Honolulu, and three quarters of a mile from the sea, is a 



Aliapaakai Group. . . 



region of tufa craters of considerable interest, extending over ten square miles, 

 and bearing marks of greater antiquity than any other similar formation on Oahu. Several 

 vents have coalesced, or rather the ejections of several have commingled as in the Koko region, 

 forming confluent arcs enclosing a plain almost a mile and three quarters in diameter and 



nearly level. The bounding walls are low, being on the 

 northern side two hundred, and on the south not more 

 than fifty feet high. They are formed of layers of tufa 

 of a red color, more granular than that of Leahi, but ar- 

 ranged in the same way. The inner slope and a portion 

 of the outer have disappeared from the Aliapaakai cra- 

 ters, while at Leahi the outer has suffered most. In the 

 tufa large masses of agglomerated chrysolite (olivine) are 

 found, often four or five inches in diameter, also augite 

 in dark green crystals, black mica, and garnets. Salt im- 

 pregnates the whole mass of the inner walls, and is found 

 in places on the cliffs where it could hardly have been 

 brought by human hands. A large portion of the plain 

 is occupied by the salt lake which gives the place its name (Aliapaalccu). In the rainy season 

 large quantities of water rush in from the mountains through a hole near the centre of the 

 basin, often bubbling above the surface, and extending the lake to the borders of the plain. 

 At such times the water is about three feet deep, clear and dense, and intensely salt. The 

 bottom is covered with a blue clay-like mud several inches deep, and is smooth and nearly 

 level. During the dry season when the supply of fresh water is cut off, and the evaporation 

 is very great, the lake is contracted to a third of its former extent, the water becomes oily 

 and burning to the skin, the whole bottom is encrusted with large cubical crystals of salt, 

 and along the shore the cakes of salt are sufficiently solid to bear the weight of a horse 



Fig. 20. Plan of Aliapaakai. 

 A, raised coral reef; B, spring of fresh water ; C, small crater; 

 D, large crater, generally dry. 



