512 ROBERT ANDERSON 



(See Fig. 7.) The cone is largely composed of fine-grained gray mud, 

 which on drying becomes compacted into tuff. It is irregularly 

 interbedded with lava and coarse fragmentary matter. This modern 

 center of the activity of Aso is about one mile nearer the eastern than 

 the western side of the old outer crater, but its position is roughly 

 central with respect to the whole great oval. 



The new crater is a black, ragged pit, constantly roaring and 

 steaming. (See Figs. 8 and 9.) It has sheer walls of roughly strati- 

 fied mud, the layers of which appear to dip inward, and a depth of 

 three hundred feet or more. It is oblong in shape, and is at a rough 

 estimate nine hundred feet across from east to west and two thousand 

 feet long from north to south, the long axis being in the same direc- 

 tion as that of the outer crater. Its rim is very uneven, being much 

 higher on the north and east than on the other sides. It is divided 

 into five compartments or vents arranged along the long axis, each 

 separated from the next by a steep wall of mud one hundred feet or 

 more high. The two most northerly vents are the deepest and the 

 only active ones. Occasionally when the vapor column diminishes 

 one can look to the bottom of the northern vent and see the burning 

 sulphur that plasters the lower walls and floor. The bottom is a 

 round flat disk of cracked mud looking hke the dried bottom of a 

 pond, and there is no appearance of a hole or conduit descending to 

 greater depths. The one next south of it is deeper and pours forth 

 the most steam. No glimpse of its bottom could be obtained by the 

 writer from any point upon the rim. The existence of activity in a 

 decadent stage is indicated at other points, all in the western half of 

 the Aso range, by jets of steam and hot springs. (See Fig. 11.) 



DOUBLE RIM OF THE NEW CRATER 



An interesting feature of the modern cone is a small ridge of mud 

 that circles around the western side of the summit at a distance of 

 about one hundred feet from the crater's edge. On climbing the 

 cone one reaches what appears to be the summit only to find that 

 one must descend some twenty feet into a moat and rise again a 

 similar amount before reaching the lip of the crater. The moat acts 

 as a line of drainage and carries the rain water southward along the 

 summit of the cone, parallel with its long axis, to an outlet down the 



