E. 8. Dana — Petrography of the Sandwich Islands. 463 



Of other specimens from the island of Hawaii there are two 

 specimens from Punaluu, one from the outside of a bomb and 

 the other from an a-a flow. The interesting point about these 

 is the strongly accentuated flow structure as shown in the feld- 

 spar microlites as they And their way around the occasional 

 large crystals of chrysolite and augite — the fluidal character is 

 as a rule entirely absent from the specimens before described, 

 and in general is not so common in basic as in acidic lavas. 



Specimens from western and northwestern Hawaii, Kawaihae 

 and Mahukono are again more or less vesicular chrysolitic 

 basalts. Of these rocks that from Kawaihae is the most note- 

 worthy because of the large clusters of glassy feldspar crystals 

 which give it a striking porphyritic aspect. 



5. Lavas of Maui. 



From the island of Maui about a dozen specimens have been 

 subjected to microscopical examination, of which three were 

 collected by Rev. S. E. Bishop. The most recent lavas of Halea- 

 kala are represented by three specimens, all somewhat scoria- 

 ceous. One of these is from the summit at an altitude of 

 nearly 10,000 feet, the others from the bottom floor. They 

 are all very highly chrysolitic, and of high specific gravity 

 (Gr.=3'10). The similarity of the hand specimens is so great 

 that they might almost have been taken from the same block. 

 They are dark colored, very vesicular, and highly porphyritic 

 with both chrysolite and augite. The large and well-formed 

 crystals of augite often have a narrow external zone of deeper 

 color (violet-brown) and are distinctly pleochroic. They are 

 usually mottled with inclusions of glass or iron. The chrysolite 

 shows but few inclusions. The ground mass is thickly 

 sprinkled with iron grains making it nearly opaque; small 

 triclinic feldspar needles and a secondary augite in minute 

 form are seen. In these specimens the feldspar must make up 

 but a very inconsiderable proportion of the whole. These recent 

 chrysolitic basalts in Haleakala are much more porphyritic and 

 otherwise quite different from the basalts of Mauna Loa and 

 Kilauea. 



More different still are several specimens of the older 

 lavas. One of these (29) is from within the crater. It is a 

 very fine-grained, dark bluish gray rock of uniform texture, 

 perfectly fresh and showing but few minute cavities. It is a 

 feldspathic rock presenting under the microscope a rather con- 

 fused aggregation of feldspar and augite, the latter in minute 

 grains, the whole thickly sprinkled with grains of iron. Chryso- 

 lite is occasionally noted in peculiar elongated forms, generally 

 forked at both ends, and having a border of titanic iron grains 

 as before noted (fig. 4, m). The most marked peculiarity is 



