288 The Yellala of the Congo. 
minimum breadth of fifty-one feet. At the Pongo 
(narrows) de Manseriche also, the Amazonas, 
“ already a noble river, is contracted at its nar¬ 
rowest part to a width of only twenty-five toises, 
bounded on each margin by lofty perpendicular 
cliffs, at the end of which the Andes are fairly passed, 
and the river emerges on the great plain.” 1 Thus 
the Yellala belongs to the class of obstructed rapids 
like those of the Nile, compared with the unob¬ 
structed, of which a fine specimen is the St. Law¬ 
rence. It reminded me strongly of the Busa 
(Boussa) described by Richard Lander, where the 
breadth of the Niger is reduced to a stone-throw, 
and the stream is broken by black rugged rocks 
arising from mid-channel. It is probably a less 
marked feature than the Congo, for in June, after 
the “ Malka ” or fourteen days of incessant rain, 
the author speaks of whirlpools, not of a regular 
break. 
I thus make the distance of the Yellala from 
the mouth between 116 and 117 miles and the total 
fall 390 feet, of which about one half (195) occurs 
in the sixty-four miles between Boma and the 
Yellala: of this figure again 100 feet belong to the 
section of five miles between the Vivi and the Great 
Rapids. The Zambeze, according to Dr. Living- 
1 Mr. Richard Spruce, “ Ocean Highways,” August, 1873, 
p. 213. 
