-GEOLOGIC STRUCTURE OF THE RIUKIU CURVE. 7 



1895." iSummarizinj^' the results of the above mentioned works 

 together with several others, Prof. Koto made a description of the 

 geotectonics in his "Geological Structure of the Kiukiu Curve" (Journ. 

 Geol. Soe. Tokyo, Vol Y. Xo. 49, 1897). He found in this curve three 

 parallel rows of islands. The inner row, being the same as that of 

 Doderlein consists entirely of neovolcanic rocks. In the middle row, 

 of Palaeozoic or older rocks, are found Yaku-shima, Oshima, Okinawa- 

 jimu, Ishigaki-jima and Iriomote-jima, besides other small islands. 

 The outer row, of Tertiary and Quaternary sediments, is found by the 

 following islands, viz., Tanega-shima, Mage-shima, the southern part 

 of Okinawa-jimn, the islands lying east of Okinawa, and finally Iri- 

 omote-jima and Yonaguni-jima. According to Prof. Koto, the charac- 

 teristic arrangement of the rocks is probably due to the great depression 

 of Tunghai (the " Eastern Sea " of China), and a curved fissure 

 extending for several hundred miles between Kyushu and Formosa. 



On the north oî Formosa and far to the north-west of the Yae- 

 yama subgroup, there lie a few small, barren and uninhabited islands. 

 Among them the Pinnacle group, consisting of Waheizan or Cho- 

 gyotö* (Hoa-pin-su), Köbitö (Chia-u-su), Pinnacle and Raleigh rocks, 

 belongs to the Okinawa Prefecture. The hydrographical as well as 

 topographical survey of these islands has been made by many foreign 

 and Japanese ships. Recently Messrs. M. Miyajima and T. Kuroiwa 

 liave reported respecting their situation, topographical features, &c. in 

 "■ The Journal of Geograph i/, Tokijö, Vol. XII, Xo. 141, 1900 and Vol. 

 XII, Xo. 144, 1900.'' Other islands lying nearer to Fonnosa are 

 Agincourt Is., Crag Is. and Pinnacle Is. A rough geological and 

 topographical note of these islands is found in "The China Sea 

 Directorv, \o\. Ill, 1894." Mr. Y. Saitö has visited the Crag and 



* Among Japanese, the two names Hoa-pin-su and Chia-u-su have been confused and the 

 Oiinese characters t^,||,ll|l| are incorrectly read Hoa-pin-su and ^^|l|!| Chia-u-su. 



