24 



Kihiitca iDid Manila 1. 



(HI. 



shown in Fig. 23, of a curious vase wrought from the molten lava of Halemaumau 

 with no better tools than round and charred sticks. The cooling svirface of the pahoe- 

 hoe still in motion wrinkles in the ways shown in many of the plates of this memoir, 

 and the wrinkles often become twisted into fine rope-like forms (Fig. 17), with a very 

 black and shining surface. 



Of the stony lavas there are many varieties, from the compact phonolite or 

 clinkstone which takes a good polish, and from the hardest varieties of which the old 

 Hawaiians made their adzes and other stone tools, to the very cellular form shown in 

 Fig. 21, a hard form often used for building, and the strangely elongated cells of speci. 

 mens found near the shore east of 

 Hilo ( Fig. 22). The more com- 

 pact kinds used for bxiildiug show 

 almost no cells, while that from 

 the surface quarries is more or less 

 cellular, and often well sprinkled 

 with olivine which impairs its value 

 as a building stone. Even the fairly 

 compact rocks are quite permeable 

 to water, making excellent filters, 

 and the apparentl}- smooth and 

 non-porous pahoehoe gives pas- 

 sage to rains as may be seen in 



the mountain caves. Basalt is more apt than other lavas to assume the prismatic form 

 on cooling, and many contradion specimens can be found in the gorge of the Wailuku 

 above Hilo (Fig. 25), and more perfectly detached ones are found on Kauai. 



We must not forget the ductilit3' shown in the lava falls, examples of which 

 are shown in many illustrations. In the eruption of 1S32 in Kilauea a fall of nearly 

 200 feet was continuous: a portion of this fall is shown in Plate XLVI. A driblet 

 from another fall is shown in Fig. 18. 



When, b}' violent explosions as in the eruption of Kilauea in 17S9, the lava is 



torn to pieces or ground into sand, a material is formed that under the influence of 



moisture tends to recombine into a volcanic sandstone called tufa, but this reunion of 



particles is usually, if not alwa3's, accompanied by a rearrangement of composition 



which ma}^ be decomposition or metamorphism. Tufa is not common on Hawaii, but 



abundant on Oahu, where the coast craters. Diamond Head, Punchbowl and others are 



composed of it. In the quarry on Punchbowl a tolerably firm tufa has been emploj-ed 



for building purposes, but has not proved durable. The sand may be mixed with 



[402] 



IflG. 19. IMPRESSION OP A SECTION OF ROPE 1,AVA. 



