2g N. Yamasaki 



distinct zones, niuniug ])aral]el to each other in a longitudinal direc- 

 tion. '■J'lie western zone, called Nishi-Karafuto or West Sakhalin, 

 consists of a long chain of mountains of younger geologic formation, 

 which extend nearly continuously along the whole length of the island. 

 On the other hand, the eastern zone, consisting of older formations, 

 was once a long chain of n)ountains, which, however, have since been 

 separated into several blocks by depression, making the Northeast 

 Range in the middle of the island, and the Susuya Mountains, with 

 the adjoining peninsula of Shiretoko, in the south. 



Between these two zones of elevation, is tlie central zone of 

 depression. To the north, stretches a low plain drained by the rivers 

 Poronai and Tym, which run in opposite directions, and in the south 

 is a similar plain along the Eiver Susuya and the lower course of 

 the Eiver Naibuchi. 



The West Sakhalin Mountains form the backbone of the island. 

 They are mostly composed of Cretaceous and Tertiary formations, and 

 are traversed by volcanic rocks in many places. The principal divide 

 and high peaks of this range are not, however, so liigh as those in 

 central Japan, and few of them exceed 1,400 m. in height. Mount 

 Notasam in the south, formerly well known under the name of 

 Spanberg, is 1,032 m. in height; while Mount Shiska, the culmina- 

 ting point of these mountains, and the highest mountain in the 

 island, measures only 1,382 m. The principal trend of the Cretaceous 

 formations, as well as that of the old formations in the eastern 

 zone, runs north and south, coinciding with that of the i:irincipal 

 mountain chains ; while the Tertiary mountains on both sides of the 

 Cretaceous formations, although running to some extent ]i)arallel to 

 them, have a difterent trend, northwest to southeast. Volcanic rocks 

 occur in many localities. They consist of andesite, basalt, and 

 agglomerate. Sometimes they exist as isolated cones like the well- 

 known Mount Notasam, or again, they form volcanic groups like 

 Ushoro, with its four cones. None of these volcanoes is active at 

 present. 



The Tertiary formation is an important element in the economic 

 geology of Sakhalin, because of the occurrence in it of many coal 

 seams. For some yeai's many collieries were worked by Russian 

 convicts along the outcrops of the seams in the coast ranges, especially 

 in North Sakhalin. Among them. Due near Alexandrovsk, Eogatzi, 

 Agneo, Mugatzi, Nainai, Petrovskii, etc., were noted, and before the 



