100 GEOLOGICAL RESEAKCHES IN 



several miles broad, being the first break, of any size, in the uninterrupted line of 

 cliffs south of the Bay of Odaszu. 



August 30th. Continuing our journey southward we followed the beach, sepa- 

 rated here by high sand hiUs from the flats of the Toshibetz, tiU. Futoro. 



Just before reaching this village we left the vaUey and came under a bluff of 

 trachytic or phonolithic lava, with a tendency to slaty structure. It has a light 

 gray base, with semi-vitreous lustre, and is cellular — the cavities being very irregular 

 in shape and lined with a grayish-blue botryoidal mineral. It contains numerous 

 crystals of a glassy triclinic felspar. 



At Futoro the volcanic conglomerate reappears as a red and brown tvifa, with 

 fragments of the lava just described and other varieties that show a regular transition 

 from this lava into a black amorphous kind closely resembling that mentioned as form- 

 ing dykes at Isoya. The strata of this neptuno-volcanic formation strike nearly N. 

 and dip to E. about 20°, and the cleavage planes of the lava bed described above dip 

 in the same direction. This lava flow seems to be at least 250 or 300 feet thick. 

 Just south of Futoro the contact between the lava and conglomerate was observed. 

 The former rock at a little distance from the contact was found to be fresh, generally 

 free from cells, and had a light gray compact base, abounding in crystals of triclinic, 

 glassy felspar, with here and there a crystal of hornblende. Its appearance re- 

 minded me strongly of some non-quartziferous felsitic porphyries. Near the contact 

 it became more earthy, and assumed the appearance of the base of the conglomerate, 

 from which it was here distinguishable only by the crystals of felspar. The whole 

 appearance of the contact seemed to indicate that the lava had flowed over the 

 surface of the older deposit before this had become compacted. 



August 31st. From Futoro we went by boat to Oouta. Not far from Futoro the 

 volcanic formations were seen to rest upon a granite or syenite, which, a little further 

 south, abuts, with a vertical line of contact, against a compact black, aphanitic 

 rock. This last was seen, in the face of a rock rising from the sea, to be traversed 

 by veins of granite which, just south of this, was found to form the high cliffs tUl 

 near Oouta. 



At Nichinbe, about three miles north of Oouta, the prevailing rock was found to 

 be a very beautiful syenitic granite, composed of greenish-white triclinic felspar, 

 brilliant hornblende, black mica, and quartz. It is traversed by a dyke of a green, 

 micro-crystalline rock, containing felspar and hornblende. 



At Oouta there is an extensive development of metamorphic rocks, consisting of 

 a fine-grained granulite of even texture, and a conglomerate-breccia of argillaceous 

 rocks. The only traces of a trend observable was in the vertical plane of contact 

 between these two rocks, and this lay N. and S. South of Oouta syenite reappears, 

 and is shown to be younger than the granulite by the numerous fragments it 

 incloses of the last-mentioned rock. 



The granulite is cut by dykes of an aphanitic rock similar to that observed 

 south of Futoro, and which we have seen to be traversed by veins of granite. 

 Finally, the conglomerate-breccia incloses fragments of amygdaloid resembling a 

 variety found in the auriferous gravel of Kunnui, and containing nodules of chalce- 

 dony surrounded by a soft green mineral resembling delessite. 



