CHINA, MONGOLIA, AND JAPAN. 83 



The view in the distance is grand. On our left the shore of the beautiful Vol- 

 cano bay forms a long, sweeping curve, parallel to which the mountains in the 

 background, covered with dense forests, appear in all the shades of green, bkxe, and 

 purple, as they stretch away on the far horizon. Far over the bay, rising as it 

 were from the sea, are several beautiful cones, long quiet, covered to the summits 

 with vegetation, while nearer, though seemingly among them, is the semi-active 

 Usu, a ruined cone whose yellow, sulphur-coated cliffs glisten even at this distance. 



We descended into the crater by a talus of pumice, and crossing to the north 

 side came to the edge of a secondary crater, or pit, in the plain. This was 

 about 600 feet in diameter, with precipitous sides on which the stratification of the 

 mass of pumice that fills the bottom of the great crater is distinctly visible. 



From the bottom and sides of this pit columns of steam were rising, incrusting 

 the walls with crystals of sulphur and salts. This inner crater must have been 

 formed after the falling in of the cone, and was, perhaps, the point of exit of the 

 ashes that fell after the breaking in of the peak. 



On examining the long fissures that traverse the plam, their sides were found 

 incrusted with delicate crystals of sulphur and sulphate salts, while the pumice 

 walls were half turned to a bright red clay, impregnated with these crystals. 

 Putting my thermometer, which was graduated only to 80° C, into the steam, the 

 mercury instantly ran up to that point. 



The recent covering of pumice conceals, in most places, the true structure of 

 the mountain, as it forms a deep mantle over every slope not too steep to retain 

 it. This product is grayish-white, very irregular in its porous structure, and con- 

 tains numerous crystals of felspar and grains of a translucent, greenish glass. It is 

 undergoing rapid disintegration. Bombs of black scoria were found containing 

 crystals of white felspar, and showing transition, in streaks, into pumice character- 

 ized by the same contents as that just described. 



Blocks of a grayish trachytic lava, abounding in crystals of triclinic felspar and 

 grains of the greenish glass, mentioned above, occur in the crater, and seem to be 

 the rock of which the pumice and bombs are a variety. 



The western side of the crater wall is the highest, and owes its better preserva- 

 tion to a broad dyke of rock consisting mainly of a dark paste with greenish-white 

 crystals of triclinic felspar, hornblende, and magnetic iron. The dyke has a tabular 

 structure, the plates beiirg upright in the middle and horizontal on the sides, form- 

 ing there a right angle with the cooling surface, as is the case with columnar struc- 

 ture. The rock traversed by this dyke was found very much disintegrated. 



Without visiting the top of the northern wall we could clearly distinguish the 

 original outer mantle of the volcano, in the exposed edges of different colored strata, 

 while just under the top of the western wall a stratified remnant of what was pro- 

 bably the old cone remained. The greater part of at least the western and northern 

 walls appear to be of trachytic rock. 



The general appearance of this mountain produced upon me the impression that 

 it had, before this, been a ruined cone, but was rebuilt by an eruption of pumice to 

 be again broken doAvn and given over to the levelling solfatara-action. 



Descending by the same route we returned to Skunope. 



