The March to Banza Nkulu. 269 
Fifteen minutes of hard paddling landed us at 
Selele, a stony point between two sandy baylets : 
amongst the mass of angular boulders a tree 
again showed the highest flood-mark to be 13 feet. 
Here for the first time I remarked the black glaze 
concerning which so much has been written. 1 The 
colour is a sunburnt black, tinted ferruginous red 
like meteoric stones, and it is generally friable, 
crumbling under the nails. It tastes strongly of 
iron, which flavours almost every spring in the 
country, yet the most likely places do not show 
this incrustation. Sometimes it looks like a matrix 
in which pudding-stone has been imbedded; it 
may be two or three lines in thickness and it does 
not colour the inside. At other times it hardly 
measures the thickness of paper, coating the gneiss 
slabs like plumbago. Humboldt tells us (“ Per¬ 
sonal Narrative,” ii. 243, Bohn), that the “ Indians” 
of the Atures declare the rocks to be burnt (car¬ 
bonized) by the sun’s rays, and I have often found 
the same black glaze upon the marly sandstones 
that alternate with calcareous formations where 
no stream ever reached them—for instance, on 
the highlands of Judea, between Jerusalem and 
the Dead Sea; in inner I stria, and in most coun¬ 
tries upon the borders of the Mediterranean. 
1 “ Highlands of the Brazil,” vol. ii. chap. xv. The red 
clay of the Congo region is an exact copy of what is found on 
the opposite side of the Atlantic. 
