TRUE VOLCANOES. 355 



Short. The knowledge of the existence of these mountains 

 is the result of laborious and hazardous researches. 



Evidences of pre-historical volcanic action in the great 

 continent, the interior of which between the seventh degree 

 north and the twelfth degree south latitude (the parallels of 

 Adamaua and the Lubalo Mountain, which acts as a water- 

 shed,) still remains so unexplored, are furnished, according 

 to Ruppell, by the country surrounding the Lake Tzana, in 

 the kingdom of Gondar, as well as by the basaltic lavas, 

 trachytes, and obsidian strata of Shoa, according to Rochet 

 d'Hericourt, whose mineralogical specimens, quite analogous 

 to those of Cantal and Mont Dore, may have been exa- 

 mined by Dufrenoy (Comptes rendus, t. xxii. pp. 806 810). 

 Though the conical mountain Koldghi in Cordofan is not 

 now seen either in a burning or smoking state, yet it ap- 

 pears that the existence of a black, porous, and vitrified rock 

 has been ascertained there. 65 



In Adamaua, south of the great Benue river, rise the 

 isolated mountain-masses of Bagele and Alantika, which 

 from their conical and dome-like forms appeared to Dr. Earth, 

 on his journey from Kuka to lola, to resemble trachyte 

 mountains. According to Petermann's notices from the note- 

 books of Overweg, (of whose researches natural science was 

 so early deprived) that traveller found in the district of 

 Gudsheba, westward of the lake of Tshad, separate basaltic 

 cones, rich in olivine and columnar in form, which were 

 sometimes intersected by layers of the red, clayey-sandstone, 

 and sometimes by those of quartzose granite. 



The small number of now ignited volcanoes in the undi- 

 vided continents, whose coast-lands are sufficiently known, 

 is a very remarkable phenomenon. Can it be that in the 

 unknown regions of Central Africa, especially south of the 

 equator, large basins of water exist, analogous to Lake 

 TJniames (formerly called by Dr. Cooley, N 'yassi), on whose 

 shores rise volcanoes, like the Demavend near the Caspian 

 Sea ? Much as the natives are accustomed to move about 

 over the country, none of them have hitherto brought us the 

 least notice of any such thing ! 



55 Cosmos, vol. 1, p. 244, note J. For the whole of the phenomena 

 hitherto known in Africa, see Landgrebe, Natwyescltichte der Vulkanc, 

 Bd. i, B. 195219. 



2 A2 



