east and two streams meeting and flowing south where we eventually
crossed them. One of those watercourses descended in cascades over
laminated successive flows of lava, between which thin layers of white
crystallization could be seen.

Slightly higher, at 1,250 ft., we sank again in yellow and grey ashes.

Across campos we reached another foaming torrent, flowing as usual over a
lava bed, but this time in a north-westerly instead of in a southerly
direction. That day we met with many watercourses. Having risen to 1,450
ft., we soon after found another streamlet (elev. 1,230 ft.). Again a red
lava-flow was exposed in its bed and showed heavy upper deposits of grey
ashes, with above them a thick layer of yellow-ochre sand (1,300 ft.).

The distances on the journey were measured by a watch, the speed of the
animals at the time being naturally taken into consideration. It was not
possible to use the usual bicycle wheel with a meter attached, which is
used with so much success in the Arctic regions or in countries where
travelling more or less in a straight line and on a level surface is
possible.

Another limpid stream flowing south-west (elev. 1,200 ft.) was reached,
then more deep sand and ashes. After that we came to a thick growth of
bamboos and brush on reaching the banks of a streamlet winding its way
north.

Travelling up and down, all day and day after day, over those undulations
became tedious work--red sand, whitish sand, grey ashes, all the time.

[Illustration: Typical Brazilian Plateau, showing Work of Erosion.]

[Illustration: On the Plateau of Matto Grosso.

(Alcides in foreground.)]

On the west side, on descending the last prominence we at last came to a
slight variation in the geological composition of the country. After more
white sand and ashes had been passed, we came upon great stretches of
greenish grey granite exposed in huge domes and much striated, with
parallel grooves on its surface so deep that they almost looked as if
they had been incised by a sharp tool. These grooves were,
nevertheless, naturally caused by the sharp friction of sand and water, I
think, and also by sand blown over those rocks with terrific force by
winds of inconceivable vigour. All the way down our descent we travelled
over that striated rock. It had become exposed to the air, but must have
once been buried under sand and ashes like all the rest of that region.
Curious vertical cracks were to be noticed in severa