434 
NATURAL HISTORY OF AFRICA. 
phyry, syenite, greenstone, serpentine, marble, 
and conglomerate* 
1. Granite. 
This rockj which is a compound of* felspar, 
quartz, and mica, is met with in Upper Egypt, 
as near to Cosseir ; also at Tetuan in Algiers, in 
Darfur, and in the great ranges of mountains at 
the sources of the Senegal. My enterprising, but 
imfortunate friend Dr Smith, one of the sufferers 
in the calamitous Congo expedition, met with 
granite in different places as he ascended the river 
Congo. It varied considerably in the size of its 
concretions ; one variety, forming what is called 
the Fetische roch^ had concretions of felspar from 
1 to 200 feet in circumference ; a magnitude far 
exceeding that of any of the granites hitherto 
noticed by mineralogists. The Khamkiesberg, to 
the northward of the Cape of Good Hope, is of a 
granite, which is disposed in round globular con- 
cretions, often of enormous magnitude. Thig 
rock is traversed by veins of different kinds ; 
some of them are filled with quartz, others with 
that beautiful mineral named Prehnite, or with 
ores of various descriptions. Barrow describes a 
hill under the name of Pearlberg, to the north of 
the peninsula of the Cape of Good Hope, which 
is remarkable for its shape. It has its name from 
a chain of large rocks, like the pearls of a neck- 
