GEOLOGIC STRUCTURE OF THE RIUKIU CURVE. 55 



form the Pinnacle Group und are nauied Hou-pin-su (Waheizuii), 

 Chia-u-su (Köbitö or Kuba-shima), the Pinnacles and Raleigh (Sekibito 

 orKume-aka-jima). These islands have been visited by Messrs. Miya- 

 jima, Kuroiwa and others. f Hoa-pin-su, the largest island in the 

 group, is in lat. 25° 47' 7" X and long. 12:^ oO' oO" E, at a distance 

 of 90 miles from the western edge of Miyako-jima, 8<S miles from 

 Hoka-banare in Iriomoto-jima, and 100 miles from the north-eastern 

 coast of Formosa. It is elongated from east to west, and is 4 miles 

 long and 3 miles broad. The highest peak in the island has an eleva- 

 tion of 1180 ft. above the sea-level. The oldest rock is diorite, found 

 on the southern coast. The greater part of the land is <jccupied l3y 

 Tertiary sandstone, which is inclined to the north at an ario-le of 

 10° — 20°, and becomes more coarse-grained toward its upper part, 

 finally passing into a conglomerate. A thin coal-seam about o inches 

 thick is found in the lower part. Raised reefs are found <3n the 

 southern, western and eastern corners of tlie island. The Binnacles 

 lie a few miles to the north-east of Hoa-pin-su, and consist of several 

 rocks such as Kita-and Minami-kojima and others, which are chiefly 

 Tertiary sandstone. The sandstone is inclined to the north at 40° on 

 the west of Minami-kojima. Raised reefs are also found on these two 

 rocks, especially on the northern side of Minami-kojima. Chia-u-su 

 lies 15 miles north-east of Hoa-pin-su (lat. 25° 58' oO" X and long. 

 123° 40' E), and is about 2 miles long and a mile wide. The highest 

 point measures 600 ft. above the sea-level. According to the |3etro- 

 graphical examination by Prof. Koto, the whole interior is a mass of 

 basalt. The Raleigh rock, situated in lat. 25° 55' X and long. 124° 

 34' E, lies about 50 miles to the east of the above-mentioned islands, 



t The China Sea Directory. Vol. III., 1894. 



t Miya-jima, ^^1",^ (Köbitö) — llie Journal of Geography, Tokyo, Vol. XII., No. 144., 1900. 

 t Kuroiwa, ^^^iJê^iètE^ (Note on the Pinnacle Islands) — The Journal of Geography, 

 Tokyo, Vol. XII., No. 141, 1900. 



