144 GEOLOGY. 



on the rocks are distributed through many works, from 

 those of Bruce and Salt to the recent narratives of 

 Markham and Von Heuglin; but the only important 

 contributions to the geology of the country with which 

 I have been able to meet are the foUowing : — 



In 1834 Eiippell published a " Sketch of the Geological 

 Formations of Abyssinia " (" Skizze der geologischen 

 Formation- Abyssiniens "), in the Museum Senkenber- 

 gianum, vol. i. p. 286. It is merely a sketch, as its^ 

 name implies, but a good one nevertheless, and contains 

 much information on the different rocks found on the 

 shores of the Eed Sea, and in Agam^, Adowa, Temben, 

 Simen, and around the Lake Tzana or Dembea. All 

 the Simen hills and the whole country around Lake 

 Dembea consist of volcanic rocks. I must differ, how- 

 ever, from Dr. ElippeU on one point. He speaks of the 

 massive hiUs of Senaf^ as of hardened marl {Kalkmergel). 

 As already stated, they appeared to me to be of a kind 

 of claystone passing into trachyte. 



A letter from M. d'Abbadie, published in the Bulletin 

 de la SoG. GSologique for 1839, voL x. p. 121, gives, 

 in very few words, an excellent description of the coast 

 near Massowa (which he considers an alluvial formation 

 daily increased by the effects of torrents), and of some 

 geological phenomena observed on the route between 

 Massowa and Gondar. The high temperature of the 

 springs in Samhar is noticed, and, on the highlands, the 

 remarkable masses of sandstone with perpendicular faces. 

 In M. d'Abbadie's opinion, the form of the mountains of 

 Tigr^ is not due to the effect of tropical rain. 



