12 mi^-m^Kii 7 7 MftK;^^ 



I obserxed the whole length of the Japanese portion of the Poronai river from a 

 boat. On the south, both the Susuya and Takoi rixers were only visited within a 

 small limit. 



The Median Depression. 



Before 1906, we had no reliable map of the river Poronai accessible, and the 

 place-names on it were often very carelessly copied from one map into another. It 

 is felt that a certain knowledge of at least three different languages, Ainu, Orokko, 

 and Gilyak is there necessary, all of which occur in the names. Such a complexity 

 of nomenclature is found in no other place in Sakhalin. This great river has large 

 branches onh' on the western side. On the eastern side, Muigö and Bolmöksha 

 are worth mentioning. Many tributaries show narrow mouths, compared with their 

 width a little above them. The main river is about 230 meters wide at the mouth 

 and about 45 on the 50tu. Parallel. The river is navigable up to Poroto, with a small 

 steamer of about 4^ ft. draught. The main course shows a great meandering, 

 which produced several crescent-shaped lakes, by drift-wood choking up one of the 

 canals, into which the river is often split up. The hugest heap of this wood is found 

 about 8 km. direct distance frorii the 2nd. Astronomical Point. It was a good piece 

 of labour to remoxe a i)art of the accumulation, measuring about 500 meters in 

 length, by blasting the wood with picric jiowder. The river-bed seldom shows in 

 the Japanese part pebbles larger than 20 cm. in diameter. Both sides of the river 

 are flat plains, with the exception of only a few places above Bolmöksha, where 

 the spurs of hills reach the river and end abruptly in high cliffs of volcanic rocks, 

 sometimes more than 50 meters in height. Where the flood-water has eroded away 

 a margin of the tundras, the formation of peat is best studied. A gray clay usually 

 forms the basement of the peat, which attains the thickness of more than 6 

 meters. Otherwise the main river shows nothing of geological interest. 



However, the pure forests of poplar-trees {I'opuhis siiavcolens), and of larches 

 {Larix dahnricci), the forests of Picea ajancnsis mixed with A lues sachalincnsis, 

 and those of birches {Betula alba and Ermanni) attract the attention of all 

 observers, especially in Autumn, when the leaves assume the beautiful colours 

 peculiar to themselves. The luxuriant growth of such and other trees is by no 

 means welcome to surveyors, concealing nearly everything at a short distance. 

 In good weather one can enjoy the distant sceneries of the gigantic mountain 

 Ninkutnujun-i or Ambarmait (about 1200 meters high, according to KAWASAKI 

 who ascended it), together with elevations connected with it. The lower 



