106 GEOLOGICAL RESEARCHES IN 



breccia, altered in great part to a wacke and strongly resembling palagonite-tufa. 

 Bordering the eastern end of the southeastern peninsula, we have seen the repre- 

 sentative beds of this formation, but differing from those of the west coast in that 

 the inclosed fragments have more the character of quartziferous trachytic porphyry, 

 thus approaching closely in character to the wall rock of the Esan crater and its 

 recent ejecta, as also to the rock of Hakodade peak. 



The only traces of fossils observed in this formation, were some fragments of the 

 spines of an Echinoderm found near Washinoki. 



The presence of these deposits over so large an area, and the fact that they 

 always contain beds of coarse material, points to a corresponding range of volcanic 

 activity. The same is indicated in the numerous lava flows and dykes that are 

 intimately associated with these beds. 



They are probably of submarine origin, and since their formation the island has 

 undergone many changes of level. A large part of Southern Yesso was under 

 water during the deposition of these deposits ; it seems to have been gradually 

 elevated and submitted to littoral erosion, forming the different terraces, and then 

 to have been partially submerged to receive the recent terrace clay deposits. 



This recent terrace deposit exists as beds of clay, almost exclusively, along the 

 southern slope of the southeastern peninsula, and bordering the western shore of 

 Volcano bay, and in depressions inland from this, as in the valley of the Toshibetz. 

 Along the west coast where the depth of water is great, and the coast precipitous, 

 this deposit rarely exists as clay, and then only bordering deep indentations like 

 the Bay of Odaszu ; but it is perhaps partially represented by the gravelly covering 

 of the volcanic conglomerate terraces. As has been already stated, this terrace- 

 clay deposit abounds in the remains of recent Mollusks. 



After the elevation of these recent terraces, and after the action of an extensive 

 erosion, there were formed the auriferous gravels of Kunnui, and finally, more 

 recent and still progressing, subaerial deposits, as the volcanic-ash beds around 

 Comangadake. 



Very little is known of the physical character of the rest of Yesso. Volcanic 

 cones, extinct and active, seem to exist throughout the island. Coal occurs at 

 several points on the east coast, and several ammonites and a piece of obsidian were 

 shown to me by the Governor of Yesso, as coming from the Monbetz creek, on the 

 northern coast. 



The island receives an additional interest from being a point of intersection of 

 three lines of upheaval, and evidently owes its remarkable shape to this fact. 



The first of these lines is represented by the northwesterly trend, of that portion 

 of the island extending from Esan volcano to the mouth of the Toshibetz, and this 

 is also the trend of the uplifted metamorphic strata ; indeed the southeastern 

 peninsula seems to be an anticlinal axis, the dip of the beds being on both sides, 

 along the coast, toward the sea. This is also the trend of the peninsula south of 

 Strogonoff bay, and of the northern coast line. 



The second line is that extending from the headland of Matzmai, northeast 

 through the longer axis of the island and of the Kurile chain to Kamschatka. This 

 determines also the northeasterly course of the eastern coast line. 



