INTR OD UCTION. 145 



A much longer " Eapport geologique et mindralogique 

 sur la Province de Tigr^," by M. Vignaud, published in 

 the same Bulletin for 1843, vol. xiv. p. 492, consists 

 mainly of an account of the country around Adowa. The 

 volcanic rocks in the neighbourhood of the Eed Sea are 

 mentioned, and the destruction of ancient Adulis attri- 

 buted to a " general movement " connected with them, — 

 a view which appears to have found favour with several 

 travellers, but for which I am unable to find any 

 authority. Most of the volcanic rocks on the shores of 

 the Red Sea are certainly far more ancient than Adulis, 

 and the destruction of the town is more probably due to 

 political than to volcanic causes. M. Vignaud's petro- 

 logical nomenclature is so peculiar, that his account is 

 not easily understood. He gives a minute description of 

 the rocks met with between Adowa and the Mareb, and 

 appears to regard all, including the volcanic formations, 

 as of transition age. Unlike M. d'Abbadie, he considers 

 that the violent rains, by removing the soluble portion of 

 the rocks, such as alumina and lime, have hollowed out 

 the ravines. 



In the Comptes Rendus for 1841, vol. xii. p. 732, is 

 an abstract of a memoir by M. Rocher d'Hdricourt, on his 

 first journey from Tajurra to Shoa. He especially refers to 

 the presence of volcanic rocks, and of hot springs. A 

 brief account of the second journey of the same writer 

 appears in the Comptes Rendus for 1845, vol. xxi. p. 883. 

 It contains nothing of geological importance ; but in the 

 Bulletin de la Soci6t6 Geologique de France for 1846, 

 p. 541, the same author gives a brief but still much more 



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