great destructive volcano Unzen-dake springing up to nearly 5,000 feet on the peninsula of Shimabara over across the gulf. One travels to Aso-san as one chooses, either on foot, in a jinrikisha, or in the funny little perambulating dry-goods box known as a basha, the Japanese adaptation of the English stagecoach. We preferred to walk, and upon leaving the plain we enjoyed many picturesque miles up the cascading stream Shirakawa. For the first night out from Kumamoto we stopped at a modest little inn, being driven by a pouring rain to take shelter at the hamlet of Tateno, which is perched high up on the side of the canyon that the road follows, at an elevation of about 1,200 feet above the sea. From there on the canyon of the Shirakawa becomes more precipitous in outline, and a short tramp in the early morning along the mountain slopes above it brought us to its brink at a point where it forked and cut squarely across our path. Here, pillared walls formed of roughly columnar lava, through which the stream has cut a grand gorge, drop sheer several hundred feet, and the path descends a zigzag course to their foot, where the two forks toss into one stream over a boulder-strewn bed. Near here a hot saline spring surrounded by the hamlet of Tochinoki, where many bathers come, give the first evidence of the proximity of the volcanic center.
Whichever of the two forking streams one follows, one presently comes up upon a broad plain that is surrounded by heights on every side and that curves around in the form of a great crescent. But, instead of ordinary mountains, the outer convex curve of the crescent is ringed about with an even-topped wall rising on the average about 1,500 feet, while the concave side is bordered by a great rugged mountain mass attaining a height of over 4,000 feet above the plain. The configuration of the region is absolutely unique and one is at a loss to understand its significance until later on, climbing the mountains and gaining expansive views over the whole broad domain of Aso. The truth is this: That a vast oval crater basin occupies the region, but is divided in two by a range of mountains that has risen across its center diametrically. The two portions of the crater thus cut off are the two crescent-shaped plains, whose level bottoms are formed by the old crater floor, whose outer surrounding walls are its rim, while the inner side of each is walled in by the great dividing range. There is but one opening in the ramparts hemming in these basins. It is where the western end of the central range meets the bounding wall. Each of the two halves of the crater is drained by a stream, and these small rivers uniting around the base of the central range at this western end, flow through the common outlet — the grand gateway through which we made our entrance. It is 10 miles across the crater from west to east in the diameter occupied by the dividing mountain ridge, while from wall to wall from south to north it is 14 miles. These figures, it must be stated, are only estimates, but a