104 GEOLOGICAL RESEARCHES IN 



cellular rock with amorphous base, containing abundant crystals of nornblende and 

 felspar. The cementing material is a more or less yellowish mineral, with the 

 lustre of wax, and easily scratched with the knife. This mass also abounds in 

 crystals of hornblende and felspar, and is cellular in the same manner as the 

 inclosed fragments. Specimens show a transition from one to the other, and this is 

 especially observable around the cells in the fragments. The general color of the 

 rock is dirty yellow. If this be not a true palagonite tufa it must be closely 

 related to it. 



The strata of this formation dip gently, on the western slope, towards the Japan 

 sea, and on the eastern slope, towards Volcano bay. They consist of two principal 

 members, the lower, a fine-grained, soft tufa with black mica and fragments of 

 nearly decomposed pumice ; and the palagonite tufa, if I may call it such, as the 

 upper member. 



At about half way between the mines and the sea we came again upon the 

 argillaceous rock of the mines, containing the same characteristic fossil, but un- 

 metamorphosed, and presenting itself as a soft gray argillaceous shale. 



At the village of Yurup, on Volcano bay, we came into the road followed in 

 going north, and completed the circuit of this itinerary. 



Without attempting, in the absence of necessary data, to determine more closely 

 the ages of the rocks referred to in the preceding pages, they may be generally 

 classed as follows : — 



I. Older metamorphic. 



II. Pluto-neptunian. 



III. Recent, including the marine terrace deposits. 



IV. Eruptive, of aU ages. 



The first of these divisions contains all the sedimentary rocks that were observed 

 to be older than the volcanic tufa-conglomerate formation. They are rocks that 

 vary widely in character, and perhaps as widely in age. Forming the skeleton, of 

 at least the southern part of Yesso, they are almost everywhere concealed by the 

 younger deposits. 



The most highly metamorphosed and perhaps the oldest strata observed are the 

 granulite and conglomerate-breccia beds of Oouta, on the west coast. These last 

 are made up of older argillaceous and amygdaloidal rocks, but are also older than 

 three varieties of eruptive rocks — aphanitic trap, syenitic granite, and a greenstone 

 trap, apparently diorite. 



The greatest part of the southeast peninsula, lying between Volcano bay and the 

 Straits of Tsungara, is formed of fissile clay slates with subordinated beds of sand- 

 stone and conglomerates, the uplift trending nearly as the peninsula, about N. W. 

 by W. These strata are traversed by frequent dykes of the characteristic white 

 quartziferoUs porphyry, and varieties of greenstone, the latter being yoimger than 

 the porphyry. 



At Wosatzube, on the northern side of the peninsula, there are beds of silicious 

 schist, having also a northwesterly trend, and strata of a similar character occur 

 at Kudo, on the west coast, associated with subordinated clay slate and beds of a 



