1842.] Capt. NewholoVs Geological Specimens. 1133 



the floor of an extinct crater, surrounded by an irregular 

 fringe of black jagged peaks, save where a great gap on 

 a level with this floor, opens upon the sandy shore of the 

 Arabian sea. Another but narrower, gap cleaves the wall 

 from summit almost to its base in a North and Southerly di- 

 rection, affording a communication, jealously guarded, with the 

 harbour of Back Bay. It is stated that native quicksilver has 

 been found in the basalt of Aden by Dr. Malcolmson, in the 

 reddish vesicular lava which is seen at Steamer Point, and 

 which prevails pretty generally on the peninsula. It occurs 

 in minute globules, adhering to the side of the cavities of the 

 rock. Native quicksilver is found in primitive rocks, dark 

 fossiliferous slates associated with Jura limestone and trap in 

 the carboniferous series in small quantities. Its appearance 

 therefore in a volcanic rock, so recent as that of Aden, is novel 

 and interesting. I found abundance of rock salt, and a little 

 sulphate of lime in the basalt of one of the islets in Back Bay, 

 and pitchstone, calcedony, incrustations of carbonate of lime, 

 kunker or travertine in that of Aden. In some places, the basalt 

 is thinly coated with a powdery mineral of a sulphur yellow 

 colour, resembling the chloruret of iron, seen tinging the 

 lavas of Etna and Vesuvius near the summits. The basalt 

 of Aden resembles strongly the newer basalts of the Puy de 

 Dome, in Central France. 

 1 1. Granite, peninsula of Mount Sinai. This peninsula consists of 

 a central cluster of granite and porphyritic rocks, of which the 

 peaks of Sinai, Horeb, and St. Catherine are the nucleus, 

 rising through uplifted hypogene schists, penetrated and altered 

 by countless basaltic dykes ; the whole are set, as in a frame- 

 work in the sandstone and limestone, which fringes the coasts. 

 Of the former is composed the celebrated mountain bell, 

 Gebel Nakhus ; the latter appears identical from its fossil and 

 mineral resemblance with that of the Mokattem and Libyan 

 ranges of Egypt, from which it is now separated by the coral 

 bedded waters of the Red Sea. 

 Indications of volcanic agency are said to exist near Ras Mahommed 

 at the South apex of the peninsula ; and I have traced them from the 



