The Yellala of the Congo. 285 
and schist, banded with quartz—Tuckey’s great 
masses of slate. This is the “ Terrapin ” of the 
Nzadi. The eastern fork, about 150 yards broad, 
is a mountain-torrent, coursing unobstructed down 
its sandy trough, and, viewed from an eminence, 
the waters of the mid-channel appear convex, a 
shallow section of a cylinder,—it is a familiar 
shape well marked upon the St. Lawrence Rapids. 
The western half is traversed by a reef, connect¬ 
ing the islets with the right bank. During August, 
this branch was found almost dry; in mid-Septem¬ 
ber, it was nearly full, and here the water breaks 
with the greatest violence. The right bank is 
subtended for some hundred yards by blocks of 
granite and greenstone, pitted with large basins 
and pot-holes, delicately rounded, turned as with 
a lathe by the turbid waters. The people declare 
that this greenstone contains copper, and Pro¬ 
fessor Smith found particles in his specimens. 
The Portuguese agents, to whom the natives care¬ 
fully submit everything curious, doubt the fact, as 
well as all reports of gold ; yet there is no reason 
why the latter should not be found. 
The current whirls and winds through its tor¬ 
tuous channels, which are like castings of metal, in 
many distinct flows ; some places are almost stag¬ 
nant, suggesting passages for canoes. Here the 
fishermen have planted their weirs; some are 
wading in the pools, others are drying their nets 
