364 
APPENDIX. 
limestone appears to be nearly of the same era with the Calcaire 
Grossier of Paris, and is separated only by a large desert plain from 
the deposit of shells last mentioned at Bonjem. The probable 
connexion of these strata with the tertiary formations in other 
adjacent parts on the coast of the Mediterranean, has been already 
suggested. 
5. Soft, highly calcareous marl stone, of a light mottled gray 
colour, resembhng in appearance the chalk marl of England : it is 
said occasionally to be streaked with red, and to contain modules 
of flint. It occurs in the Mountains of Mejdool, in lat. 26. 
6. Quartzose sand dispersed through a matrix of indurated 
green clay, and affording the materials of which the town of 
Traghan is built. 
It is probable that these two last specimens, 5 and 6, are from 
strata not more ancient than the chalk of England, and possibly 
connected with the tertiary formations. No. 3 and 4. 
NEW RED SAND STONE. 
7. Sand collected fifty miles on the north of Sockna, during a 
gale of wind from the drift sand, which is blown about the desert. 
It is composed of extremely minute grains of red semi-transparent 
quartz ; observed with a lens, these grains appear to be rounded 
fragments, and present no crystalhne facets. They possess, in a 
strong degree, that pecuHar tint of red, which has caused the 
name of red sand stone to be apphed to certain extensive forma- 
tions which it pervades in Europe. 
The frequent occurrence of salt springs, and of rock salt and 
gypsum in the deserts of Africa, goes far to identify the sand of this 
continent with the new red sand in the south of England, which is 
characterised by containing similar mineral substances. It is still 
farther aUied to it in being accompanied by strata of calcareous 
breccia and beds of Hmestone ; in all of which magnesia is a con- 
siderable ingredient. 
