368 
APPENDIX. 
It appears then, as far as can be collected from the few speci- 
mens above described, that on each side of the central basaltic 
chain of the Soudah or Black Mountains, the plains of the desert 
are composed of red sand and sand-stone, containing gypsum and 
rock salt, and associated with beds of dolomite and common car- 
bonate of Hme. All these characters identify most distinctly the 
sand of the desert of Africa with the new red sand-stone of Eng- 
land. There are no specimens which indicate the existence of any 
other formations on the south side of the Black Mountains from 
lat. 29° to 24°, except the marl-stone and green clay (No. 5 and 6) ; 
which lead us to suspect strata of tertiary formation in lat. 26", 
near Mejdool, on the east of Morzouk. At the north base of the 
central chain, strata belonging to the same red sand-stone formation 
seem to extend nearly to Bonjem on the frontiers of Fezzan and 
Tripoh ; where the basis formations appear, and probably repose 
on them in irregular patches in the desert that divides this place 
from the mountains on the north of the town of Tripoli. These 
mountains extend east and west nearly parallel to the coast of the 
Mediterranean, from long. 15° to 13°; but as no specimens have 
been brought home from them, it is impossible to do more than 
conjecture to what formation they belong : from notices inserted 
in the map. they appear to contain trap and calcareous rocks. • 
The nearest point from which we have a specimen is Benioleed 
(No. 4) : and this is probably referrible to the calcaire grossier of 
Paris. 
One soUtary specimen from the eastern extremity of these cal- 
careous mountains possesses no character sufficiently distinct to 
show whether it be calcaire grossier or jura hmestone. It seems, 
however, to belong to one of these two formations. 
The only specimen remaining to be described is No. 34 ; a 
yellow quartzose sand-stone, having a glassy fracture, and in some 
of its component grains having a sapphire blue colour. It re- 
