Page:Popular Science Monthly Volume 71.djvu/44

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38
POPULAR SCIENCE MONTHLY

narrow and ragged as it approached the rocky mountain top. At an elevation of 4,750 feet by my barometer, just under the brow of the summit, I caught a glimpse on approaching of what I took to be a lonely wild cherry tree in blossom far up here alone. It proved to be a group of bushes with their bare limbs and twigs bearing little balls of snow, remnants of the winter.

From the mountain top a magnificent view opened and led me for the first time to a comprehension of the structure of the region. I had come from a deep basin on the south of the Aso range and here suddenly was spread out on the north its almost exact counterpart. At about 3,000 feet below the peak on which I stood lay this other far-reaching plain which seemed to be the continuation of the southern one, while round its outer edge it was enclosed by a similar curving wall. The grandeur of the scale upon which all the lines in the scene were drawn made the outlook a most impressive one, and with the view came a sense of the magnitude of the forces that had been at work in molding the large details of such a landscape. The sight was such that it carried with it at once the appreciation of these two huge bowls as parts of a great crater, divided by a high, massive mountain partition.

This crater is almost circular in appearance. Its rim forms a smooth sweeping curve around the whole circumference, broken only at the cleft on the west where the streams pass out, and on the east where it is joined by the slope of Neko-dake. The summit of this outer wall is remarkably even and its inner side precipitous. Although it presents rocky precipices at points on its face, its general slope is by no means perpendicular, but, being steeper as a rule than ordinary mountain slopes, it has a strikingly abrupt appearance. This is especially true in the case of the northern basin, where the wall facing the south is less gashed by lines of erosion, is more sheer, and has a more perfectly preserved even summit than the wall of the southern bowl. The latter wall is furrowed by gulches that have eaten back to the summit in places and notched the sky-line of the rim. Between these gulches sharp ridges run out into the plain, some of them looking more like lava flows descending from the wall than like remnants left by erosion. Such ridges run out into the northern basin as well, and little island-like hills rise in isolated positions from the crater floor. This half, though a close counterpart of the other, is more nearly round and its walls preserve a more even height. The slope up from the floor in both basins is gentle at first at the foot of the walls and then becomes steep. The walls are formed of roughly bedded lava flows inter stratified and intermingled with mixtures of vesicular lava, scoria, pumice and volcanic sand. The harder lava layers project with vertical rocky faces, while between them softer zones have weathered away into debris slopes and produced a rough terraced effect, somewhat similar to that in the sides of the Grand Canyon of the Colorado. The height of the