d outer sides of the crater to the north would tend
to strengthen the theory that those slopes were formerly a gradual
continuation of the present inclined valley. On those slopes of the
mountain hardly any vegetation could be noticed, perhaps owing to the
fact that hard volcanic rock existed under the thin surface padding of
yellowish earth.

The valley was buried in red and grey lapilli and ashes, finely broken up
marble cubes, and fragments of other forms of crystallized rock.

As we proceeded from camp Fogasso, the northern slopes of the crater
became divided into huge furrows, the vertical upper part of the crater
displaying vividly rich red tones. The crater was castellated at the
summit, like the walls of a fortress.

The geological formation of that portion of the Matto Grosso plateau
interested me greatly. Each individual spur, taken separately, showed
slopes sometimes abrupt, sometimes well rounded, separated from the next
spur of hills by a V-shaped or angular, or else a concave hollow. At the
bottom of those hollows one did not find the slopes continuing the line
of the crater, but the valley was there absolutely flat and cut the line
of the slope sharply. It would almost appear as if a subsidence of the
soil had taken place in that particular locality, or else one might
speculate whether those abrupt hills had not been the walls of what was
once a subterranean volcanic cauldron--the flat valley, in which we were,
having been the bottom of that cauldron. What little rock one found in
the river bed in this valley showed signs of having been exposed to
intense and prolonged heat, and so did the brilliant red summit of the
hill range, which was also of the deep red typical of hard-baked rock.

[Illustration: The Paredaozinho.]

[Illustration: Typical Scenery of Matto Grosso.]

The scene which I had before me there in Matto Grosso greatly reminded me
of a similar basin I had seen when the great Bandaisan mountain in
Japan was blown up by a volcanic explosion and left merely the bottom
part of its gigantic internal cauldron with vertical red walls around it.
With the exception of scanty and anaemic grass and a few stunted trees,
there was hardly any vegetation noticeable. The Fogasso stream, on the
bank of which we camped, flowed in an easterly direction into the
Araguaya.

The temperature on the plateau was ideal--min. 63 deg. Fahr. during the
night; max. 75 deg.. We were at an elevation of 1,450 ft.

O