198 ART. 2. — B. koto: 



approach the piedmont hills, thick debris covers the foot, and 

 the valleys are choked with coarse cobbles through which slender 

 streams make their difficult way to the sea. The cobbles and 

 shingles are of such a large size that only glaciers could have 

 carried them. I can only suppose that there was at the end of the 

 Diluvium a great meteorological change from dry climate to the 

 wet ^', which inaugurated the beginning of the Recent period. 

 Abundant precipitation and floods caused energetic erosion, degrad- 

 ing mountains and widening valleys, spreading loads and burying 

 bottoms, while the fine silt and sand were carried down to sea. 

 What we now see as the Alluvial deposit in the interior is the coarse 

 load left behind by the sorting and subtracting action of running 

 water. This climatic amelioration then prepared the way for the 

 wandering of t1ie prehistoric man who entered the peninsula from 

 the north. The dolmens and stone mounds with side entrances '' 

 which I saw may be remains of the primitive inhabitants. 



In short, this is the general aspect of the Alluvium. Allu- 

 viated ground is scarce on the east coast, and a few patches 

 occur on the south along the bays, indentations and debouchures 

 of rivers ; but along the Yellow Sea, on the contrary, extensive 

 low flats are alternately exposed and hidden by the unique tidal 

 difference of more than thirty-four feet. 



The flats are thinly covered with sand. On one occasion 1 

 examined them at Che-mul-plio, and found to my surprise that 

 the sand cover was only a few inches thick. The underground 

 was loose original rocks disintegrating by a selective decomposi- 

 tion of their components. The flats therefore had resulted from 



1) la non-glaciatecl regions, such as Africa, the Drift period was represented by the 

 Phwhl period. 



2) Near the village of Nak-tong on the bank of the Nak-tong gang. 



