Curious Domes of Lava with Upper Stratum of Earth, Sand and Ashes.
Great Undulating Campos of Matto Grosso.
The streamlet flowed east into a larger stream, which we also crossed, and which flowed south-west.
It seemed to be getting colder at night as we went westward (May 18th, min. 57° Fahr.), whereas during the day the temperature was hot—max. 97° F. As early as 9 a.m. the thermometer already registered 85° in the shade, and not a breath of wind. The elevation was 1,150 ft. The sky was in streaky horizontal clouds to the east, and thin misty clouds to the south—cirro-stratus.
One of my horses having strayed away a long distance, we only left that camp in the afternoon after the animal had been recovered. We rose quickly over the usual red volcanic sand held down in its place by the vegetation—rather anæmic at that particular spot. Higher up we again sank in the white and yellow ashes, with occasional zones covered by small, angular, black-baked débris.
Ants seemed to flourish happily in that region, for the ant-heaps were innumerable and of great size, several with towers about 6 ft. in height, resembling miniature mediæval castles.
Having risen—all the time over grey and white ashes—to 1,420 ft., we found ourselves again upon open campos with a splendid view of the flat-topped range we had already seen to the north and of another to the south. At the angle where the northern range changed its direction slightly there stood a high prominence of peculiar appearance. The range extended west, where it ended, into a broken cone—as I have already stated quite separated by erosion from the main range. All along the range in the section between the prominence at the angle and the terminal cone could be noticed three distinct level terraces and several intermediate ones—not yet well defined nor continuous along the whole face of the range. About half-way along its length, a semi-cylindrical vertical cut was a striking feature, and appeared from a distance to be the remains of an extinct crater. It may be noted that where that crater was, the range was higher than elsewhere. Its summit, with an undulating sky-line, lay to the west of it, no doubt formed by erupted matter. Other great vertical furrows were noticeable not far from the crater and to the west of it.
