98 B. KOTO : THE GEOLOGIC STRUCTURE OF 



Following an idea started by L. v. Buch, Prof. E. Saess recently 

 made a critical study of the geology of the Lesser Antilles, 

 which has resulted in the recognition of three zones, viz., (1) the 

 first or inner zone within the concavity of the curved chain, 

 which is exclusively of young volcanic origin ; (2) the next 

 which comprehends the mountainous islands ; and (3) the third, 

 exterior belt which comprises the Miocene and Quaternary for- 

 mations. 



We meet, according to Wichmann, the analogue of these 

 zones in the Banda Sea with the innermost volcanic arc, cons- 

 tituted by a chain of islands from Roma to Banda, corres- 

 ponding with that of the Lesser Antilles, caused by the falling 

 in of the crust inside of the above arc. This great sink is itself 

 the Banda Sea, and earthquakes frequent the peripheric zone, as 

 in Amboina, Ceram, and other isles belonging to the series. The 

 second and even the third zone can also be made out, of which 

 enough has been already said in the foregoing pages. 



We have a striking representative of geologic homology of the 

 threefold concentric arcs in the Riu-kiu islands,'^*^ which stretch 

 from the north of Taiwan (Formosa) to the south end of Kiu-shu, 

 in which arcs the characteristic three zones can be more easily 

 recognisable than those of the Banda and the Lesser Antilles. 



It is to be expressly remarked that in the recent work of 

 Verbeek,^^^ the volcanic zone of the Banda group is made to go 

 round in enclosed ellipse which passes through the South-west 

 Islands, and then through Gunung Api, off Lucipara and the 

 Tortoise isles, deviating from Wichmann's arc. 



34) Koto, Chlshitsu-gaku-Zasshi (The Japan Geological ^lagazine), Vol. IV. 



35) Verbeek et Fennema, ' Description Géologique de Java et Madoura ', 1896. 



