THE JELL ALA OF TIIE CONGO. 
123 
wide above the Cachoeira de Paulo Alfonso, is choked 
to a minimum breadth of fifty-one feet. At the Pongo 
(narrows) de Manseriche also, the Amazonas, “ already 
a noble river, is contracted at its narrowest 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 
CASCADES. 
the great plain.” * Thus the Yellala belongs to the class 
of obstructed rapids like those of the Nile, compared 
with the unobstructed, of which a fine specimen is the 
St. Lawrence. It reminded me strongly of the Biisa 
(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 
* Mr. Bichard Spruce, “ Ocean Highways,” August, 1873, p. 213. 
