STRANGE GEOMETRICAL PATTERNS 
with dangerous jobs, did swarms of those little rascals 
attack us with indomitable fury. 
Another basin was met, 700 metres wide, quite shallow, 
and with rapids over a barrier of rock extending across it 
from southwest to northeast. That barrier was most in¬ 
teresting, because in many places great lava flows were 
visible; in other places masses of ferruginous rock could 
be observed, with most extraordinary patterns upon them, 
triangles, rectangles, trapeziums, and all kinds of other 
angular geometrical patterns, such as we had met before 
on the high plateau of Matto Grosso. 
We stopped in the middle of the day on an island 
1,200 metres long, from which we obtained a fine view of 
the hill range looming before us from west-southwest to 
east-northeast on the right bank. 
I was having great trouble with my chronometer, 
which the many jerks, falls, and baths did not seem to 
improve. I checked it whenever I could by observations 
of local time and by other watches which I carried. But 
all my instruments were beginning to feel the effects of 
that journey very much. The wonder to me was that 
they had got so far in as good condition as they were, 
considering all we had gone through. 
Our lunch was speedy, as we had nothing to eat. The 
moment I had finished my observations for latitude and 
longitude we started off once more, my men keeping their 
eyes all the time on the forest on the look-out for nut-trees, 
the river that day giving us no fish at all. 
Within ten minutes we had shot two powerful rapids, 
and in one place went over a dangerous submerged wall 
of rock extending across the river from east-southeast to 
west-northwest. 
The men, very hungry, were extremely quarrelsome 
that day and insulting to one another. The canoe went 
broadside down a rapid we met, the men gesticulating 
instead of paddling along as they should have done. With 
185 
