OF THE HAWAIIAN ISLANDS. 459 



it is exceedingly common on all the tufa cones on the ancient reef, and sometimes is of 

 quality and quantity to be used as chalk, especially the deposits at Le&hi and Laeloa. In the 

 caves at Haena, on Kauai, the roof is in many places covered with a thick incrustation of 

 agaric mineral, and specimens were obtained several inches thick. I am inclined to refer to 

 calcite the insoluble scum which was mentioned as occurring on the water in the second cave. 

 It was here that the incrustation formed extensively, and the unevaporated water which had 

 percolated from above dropped constantly from the roof. The incrustations are mamillary 

 and botryoidal, and of a reddish-yellow tinge, often cellular in structure. 



The coral rock is burned for quicklime, which is not, however, considered of so good 

 quality as that made from other limestone. The calcareous matter, however, cements 

 together fine volcanic sand, forming the coral-shaped masses of sandstone at Koloa on Kauai, 

 the beach sandstone of Hanalei and elsewhere, and the curious sand tubes of the Isthmus 

 of Ma\ii. It also cements together the black gravel near Honolulu, forming cylindrical and 

 rounded masses, often resembling fossil bones. 



Arragonite. 



Sometimes found mixed largely with calcite incrusting caves. The crystals are small and 

 inconspicuous, and the corolloidal form is more common. 



Hawaiian Rocks. 



Fresh Lava. 



The lava spattered out of the pools cools rapidly in the air, and presents when cold a 

 glossy black exterior usually quite smooth, somewhat resembling coal tar, while the interior 

 of the drops is sometimes hollow, and oftener filled with a cellular mass perfectly vitreous. 

 The lava drops are indeed miniature volcanic bombs. Although as they are seldom projected 

 to any considerable height the contained gas has no opportunity to burst the solidified shell 

 in a rarer atmosphere ; and as the lava is still red-hot when it strikes the ground, provided 

 the pieces are more than half an inch in diameter, the drops flatten and lose completely the 

 spheroidal shape they assumed during projection. The drops are exceedingly brittle, and 

 split readily with the least jar, presenting a conchoidal fracture. The lava of which they 

 are composed is so poor a conductor of heat that a fragment, a quarter of an inch thick, 

 may be held in the hand within an inch of the red-hot extremity. 



The filamentous lava formed by the adhesion of the drops to each other, or 



*■ A Pole's lliii. 



to the surface of the pool, varies in color and fineness. During the eruptions 

 on the slopes of Mauna Loa, when the lava fountains often play to a great height, the wind 

 spins out Pele's hair in clear green or yellow threads, sometimes three feet in length and 

 rather coarse. In Kilauea, the threads are finer, 1 and although clear and transparent when 

 first formed, are soon corroded on the surface by the sulphurous vapor* so abundant there. 

 This decomposition is rapid, and on the leeward banks a strong cement is formed with the 

 dissolved silica. 



Various analyses have been made of this curious product, and as the drops are of essen- 



1 I have seen a bird's nest wholly made of this Pele's hair, tained two eggs. It is now in the possession of Mr. D. R. 

 beautifully interwoven. When found in the crater, it con- Hitchcock of Hilo. 



