264 John Hogg, Esq , on the Geography and 



Seven or eight miles to the north of this last mountain, ex- 

 tensive banks of a black small grained diabase, much charged 

 with hornblende, called tnelaphyre, occur. Strewn with crystals 

 of grey felspar of various sizes, it contains small irregular 

 masses of pyrites. Beds of melaphyre are also found in a 

 mountain between Wadis Firan and Naszb ; and among the 

 primitive mountains near Wadi Naszb, thick and horizontal 

 beds of a beautiful violet Sinaite are seen, resting on banks 

 of porphyry. 



The highly polished surface which the Sinaite often pre- 

 sents, '* has been attributed to the action of minute particles 

 of quartz, and moved over it by the winds during a long suc- 

 cession of ages. The alleged cause is certainly in operation, 

 and is known to be adequate to produce the observed effect." 



The huge granitic masses that appear isolated in the Wadis 

 of the high Sinaic district, are considered to be of a different 

 kind from any of the beds in the adjacent mountains. They 

 consist almost entirely of felspar, in '* distinct red crystals, 

 intermixed with large crystals of quartz,'' with very slight 

 micaceous laminae. Of these detached masses, that related 

 by the monks as " the rock in Horeb" which Moses smote, is 

 remarkable. A little mica, associated with quartz and much 

 felspar, places this mass amongst the true granites. Epidote 

 constitutes a portion of many of the rocks of the peninsula, 

 and is occasionally joined to a white felspar, having slight 

 streaks of red. So combined, it is not unfrequently seen in 

 the southern El Turfa range. 



I may here refer the reader to several beautifully executed 

 plates of different rocks from Arable Fetree, published under 

 Napoleon's auspices, in the magnificent work of the French 

 Scientific Commission, entitled " Description de I'Egypte," 

 (Seconde Edition), Histoire Naturelle. Tome 2. Bis. Paris, 

 1826. PI. 12, figs. 1-9, represent well-engraved specimens 

 of ^^ ^oehe^ Porphyrithiques,^'' fYOVCL Wadi Firan, and Gebel 

 Horeb. PI. 13 gives examples of " Porphyres, Sindltes, Gres^"* 

 &c., from Wadi Naszb, Mukatteb, and Gebel Mousa. PI. 14, 

 granites from Gebel Mousa and Gebel Horeb ; and PI. 15, 

 different primitive rocks from the coasts of the ^Elanitic 

 or Eastern Gulf. 



