NATURAL HISTORY OF AFRICA. 433 
remarked that beds of rock salt occur under strata 
of sandstone in Southern Africa. 
Coal 
Hitherto scarcely any traces of coal have been 
met with in Africa. The only instance I find re- 
corded by travellers, is the following by Mr Bar- 
row, where coal was found at the Tyger-berg, in 
the country to the north of the Cape of Good 
Hope. It is described as a bed of imperfect coal 
resting upon clay, and covered with clay and white 
sandstone. The coal is ligneous, or of the nature of 
brown coal, and contains intermixed iron pyrites. 
• 
Trap. 
Trap rocks of the nature of basalt occur in some 
places in the Atlas range, apparently connected 
with limestone : rocks of the same description are 
met with at Sierra Leone, and abundantly in the 
limestone hills of Harutsch in Fezzan. The lime- 
stone hills that extend from Fezzan to Tripoli also 
contain extensive formations of trap, and it is re- 
marked, that these rocks occasion considerable va- 
riety in the position of the limestone strata ; ow- 
ing to the crystallization of the trap rocks, if they 
are of aquatic formation, or to the action of the 
lava, if they are of volcanic origin. 
Detached hills of amygdaloid, also a trap rock, 
VOL. II. E e 
