192 
PHYSICAL HISTORY OF THE 
ing sun of the tropics may produce upon lam¬ 
inated clays of recent origin the same effect 
as plutonic agents have produced upon the 
ancient clays, that is, it may change them into 
metamorpliic slates. 
After an hour’s walk under the scorching 
sun, I was glad to find myself at the hamlet 
of Errer£, near the foot of the serra, where I 
rejoined my companions. It w r as already noon, 
and they had arrived some time before. They 
had, however, waited breakfast for me, to 
which we all brought a good appetite. Break¬ 
fast over, we slung our hammocks under the 
trees, and during the heat of the day enjoyed 
the rest which we had so richly earned. 
Major Coutinho and myself passed three 
days in the investigation of the serra of 
ErrerA We found it to consist wholly of 
the sandstone deposits described above, and 
to have exactly the same geological consti¬ 
tution. In short, the serra of Monte Alegre, 
and of course all those connected with it on 
the northern side of the river, lie in the pro¬ 
longation of the lower beds forming the banks 
of the river, their greater height being due 
simply to the fact that they have not been 
