44 AKT. I.-B. KOTO: 



spot at Chhya-ryöng on the north of the American Mines of Un-san. 

 The said structure seems to prevail mainly to the east of the com- 

 pound ridge of Thai-Päik-san and Nang-nim, which together form 

 the present back-hone of the Korean Peninsula. 



There are three ridges of the Thai-Päik-san range in West 

 Kai-ma. As they are inseparable from those in the land of Paleo- 

 Chyo-syön, it will be convenient to treat them in the sequel. 



C. THE PALEO-CHYO-SYON LAND. 



Between the axes of mountains of the Sinian and Liau-tung 

 directions which seem to join in East Kai-ma and Yuk-chin, there is 

 present a wedge-shaped tract of land inserted between them, which 

 remained in a neutral state, or rather took a retrogressive movement 

 to the south-west between the two struggling forces. Geologically 

 speaking, it is a folded Sinian land. Lying to the north-west of the 

 trench of Chyuk-ka-ryöng, which separates South from North Korea, 

 this Intersertal makes up the southern half of the latter, being bounded 

 on the north by Kai-ma. 



Topographically, it is the 'and of Mittelgebirge, diversely crossed 

 by ridges (Fig. 5), averaging less than 300 meters, excepting in the 

 eastern and north-eastern portions from which the waters "flow down 

 to Korea Bay, through the channels of the Tai-dong Gang" and the 

 Chhyöng-chhyün Gang.'' As may be seen from their crooked courses, 

 the rivers make their way through nearly reticulated ridges in 

 diagonal directions. Especially the Tai-dong Gang serves for the 



1) ^cIrIJI. " great-mme-stream, or'phai-syu (^?J0 -) fjlJllÖl 



