32 Foren Notices in Mineralogy, Se. 
are of the same description with those so abundantly distri- 
buted in our coal fields.” 
3. Geological notices in Northern Africa, from the Quar- 
terly Review, No. 49. 
““ A narrative of travels in Northern Africa in the years 
1818-19 and 20, &c. &c. by Captain G. F. Lyon, R. N. 
companion of the late Mr. Ritchie. 4to. pp. 382. Jon- 
don, 1821.” 
** From specimens of rock collected by Captain Lyon in 
various parts of his journey, Professor Buckland has been 
able to determine the geological structure of Tripoli and 
fezzan ; all of which may be referred to the three forma- 
tions, 1. Basalt; 2. Tertiary limestone of about the same 
age with the calemre grossier of Paris; 3. New red sand 
stone. The Soudah or Black mountains, as we have al- 
ready stated, are of basaltic formation; their direction is 
east and west, and they extend probably across the continent, 
Horneman having crossed them nearly two hundred miles to 
the south-eastward of Lyon, where they take the name of the 
Black Harutsch. Some basalt also appears in the Gharian 
mountains ; but this ridge, which runs probably to the bor- 
ders of Egypt, is composed apparently of trap and calcare- 
ous rocks—the tertiary limestone above mentioned. The 
rocks contain marine shells, particularly two species of car- 
dium, in a state of delicate preservation. Indeed most of 
the limestone formation, in every part of Northern Africa, 
appears to be loaded with fragments of organic remains, the 
most distinct of which, brought away by Captain Lyon, may 
be referred to the genera ortrea and pecten. We are in- 
formed by Horneman, that the ruins of the temple of Si- 
wah are limestone, containing petrifactions of shells and 
small marine animals; and from this place, westerly, the 
face of the rocky chain rising abruptly from the sandy des- 
ert was so crowded and filled with marine animals and shells 
and white detached mounds, as it were wholly composed of 
shells, that when taken in connexion with the ‘sea sand,’ 
which covers the desert, this vast tract of country, he con- 
cludes. must have been flooded at a period Jater than the 
