SECONDARY ROCKS. 
441 
choidal fracture, and grey or variegated colour, 
contains numerous petrifactions of shells, corals, 
and fishes. It extends from Syene to the Medi- 
terranean ; and in Lower Egypt reaches from 
Alexandria to the Red Sea, in the vicinity of 
Suez. It extends from the westward of the Nile 
onward to Fezzan, forming single hills and ranges 
of hills. In the hilly district of Fezzan, near 
Harutsch, the limestone which still prevails is 
caped and intermixed with trap rocks. The 
limestone is generally disposed in horizontal stra- 
ta, but where the trap rocks appear, the stratifica- 
tion is more or less varied in its position. In tra- 
velling from Fezzan northwards towards Tripoli, 
the continuation of the Harutsch presents ranges 
of basaltic eminences alternating with rows of 
limestone hills. A limestone of the same descrip- 
tion appears to view in the mountain ranges lead- 
ing to Cosseir 5 and in the same tract of country 
there are hills of limestone associated with gyp- 
sum. It is also met with in the lower parts of 
the Atlas range, as near to Algiers, where it con- 
tains petrified fishes ; and it is mentioned as oc- 
curring in the vicinity of Carthage. 
3. Gypsum. 
Gypsum occurs within three leagues of Cosseir, 
where it is connected with limestone,"^ and proba- 
bly also with porphyry j and it is mentioned as 
