426 NATUEAL HISTORY OF AFRICA, 
Hope, is of a granite, which is disposed in round 
granular concretions, often of enormous magnitude. 
The rock is traversed by veins, some of which are 
filled with quartz, and also by others containing the 
beautiful mineral named Prehnite, or ores of differ- 
ent kinds resting upon gneiss, or some other of the 
allied species. 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 necklace, that pass over 
the summit, and are very remarkable in their ap- 
pearance. Two of them, placed near the central 
and highest point, are called the Diamond and Pearl. 
They are said to be of very coarse granular gra- 
nite, but the hill of sandstone. The Pearl is about 
four hundred feet above the summit of the hill, and 
the circumference of its base fully a mile. The 
Diamond is larger. The central rock of the pen- 
insula of the Cape of Good Hope is granite, which 
is highest at the northern extremity, and lower 
gradually to the south. This granite is observed 
in many places covered with clay slate, and veins 
of the granite shoot from the massive rock into 
the clay slate. The higher parts of the penin- 
sula are covered with a platform of horizontal sand- 
stone. It is remarked by Professor Playfair, that the 
penetration of the slate by veins, from the mass of 
granite which it surrounds, proves that the slate,. 
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