62 ART 2.— ^B. koto: 



the bay of Mäl-gil (Washington Bay) at the southern extremity of 

 Chin-do, I saw a grayish-looking gneiss striking now N.N.W. — S.S.E. 

 with the dip S.W. One pecnKar feature to the eye of geologists 

 is the direction (N.N.W. — S.S.E.) of the channel that separates 

 the island from the mainland, and another is that the island is 

 deeply indented in the same direction. This point must have 

 some deep tectonic significance if we take into account the 

 change of the strike of the rocks. Chin-do is the out- post of the 

 south-west corner of tlie Korean peninsula, which divides the dirty 

 waters of the Yellow Sea from the blue Tung-hai. 



Usu-YONG From the old naval station Usu-uöiig, we advanced directly 



northwards on a red soil of decomposed felsophyre, which changed 

 about 6 k77i further on to the green variety at the low and narrow 

 neck of land. Here appear green and white banded rocks of 

 porphyrite and its derivatives overlying felsophyre-breccia, striking 

 eastwest and dipping southwards. The features of the landscape 

 now entirely change, the peaks becoming rather high and trending 

 east- west, and at the eastern foot I looked down on a large group 

 of mud hovels on the shore, called Mok-chhang^^. After climbing 

 over a few hill-necks of green tuff and a massive bed of porphyrite, 

 we finally came to a brink of shallow water at the north extremity 

 of the headland of U-su-y'ông, near the islet Moral-söm '^ which is 

 connected with the land at low tide. The rock is a green sheet 

 of aiigite-porphyrite •"■^ (the strike N.W. — S.E., the dip N.E.). 



1) tt: jT (lb m) or Hoa-uön 2) 'é> ^ 



3) Green siphanitic rock whicli, when examined under the raicroacopc, is seen to be an 

 aggregate of lath-shai)ed crystals of plagioclase arranged approximately ijarallel to one another. 

 They are simple-twinned, and elongated on the a-axis with a negative character in the direction 

 of the principal zone. Tlie ferro-m.agnesian mineral is all chloritized, and the same chloritic 

 substance together Asith yellow epidote fills up the interstices of the feldspar. The rock 

 efiEervesces with acids. It is probably auijlte-porphyrUc. The effusive alternates with a grayish 

 compact marl. 



