MO NATURAL HISTORY OF AFRICA, 
and the third of slate, which alternates with and 
passes into the breccia.* 
SECONDARY ROCKS. 
The following secondary rocks occur in Africa : 
sandstone, limestone, gypsum, salt, coal, and 
trap. 
1. Sandstone^ 
This rock occurs in great abundance in many 
regions in Africa, as in the mountains leading to 
Cosseir, at Tetuan in Fez, Tunis, the peninsula of 
the Cape of Good Hope, and forming great 
mountains, reaching to a height of ten thousand 
feet, to the northward of the Cape of Good Hope. 
At Tetuan it is said to rest upon granite ; in 
many of the mountain ranges in Southern Africa, 
upon clay slate or granite. It passes into a grey 
coloured quartz, and does not contain organic 
remains. It is not improbable, that much of this 
sandstone may prove, on more particular exami- 
nation, to belong to the species named quartz 
rock, or primitive sandstone, which occurs in 
vast beds in primitive mountains. 
Limestone. 
This limestone, which has a splintery or con- 
* The sarcophagus of Alexander the Great, now in the 
British Museum, is of the breccia di verde. 
