120 
AFRICA AND ITS EXPLORATION. 
Hill,” bluff to the stream, and falling west with gradual 
incline. The noise of this higher fall can hardly be 
heard at Nkulu, except on the stillest nights. 
Below the upper gate, the bed, now narrowing to 
300 yards, shows the great Yellala ; the waters, after 
breaking into waves for a mile and a half above, rush 
down an inclined plane of some thirty feet in 300 yards, 
spuming, colliding and throwing up foam, which looks 
dingy white against the dull yellow-brown of the less 
disturbed channel — the movement is that of waves 
dashing upon a pier. The bed is broken by the Zunga 
chya Malemba, which some pronounced Sanga cliya 
Malemba, an oval islet in mid-stream, whose greater 
diameter is disposed along the axis of the bed. The 
north-western apex, raised about fifty feet above the 
present level of the waters, shows a little bay of pure 
sand, the detritus of its rocks, with a flood-mark fifteen 
feet high, whilst the opposite side bears a few wind- 
wruno; trees. The materials are gneiss 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, connecting the islets 
with the right bank. During August, this branch was 
found almost dry ; in mid- September, 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 Professor Smith 
found particles in his specimens. The Portuguese agents, 
to whom the natives carefully 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 tortuous 
