334 cos^K)s. 



ains. According to Petermann's notices from the note-books 

 of Overweg (of whose researches natural science was so ear- 

 ly deprived), that traveler found in the district of Gudsheba, 

 westward of the Lake of Tshad, separate basaltic cones, rich 

 in olivin and columnar in form, which were sometimes inter- 

 sected 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 un- 

 known regions of Central Africa, especially south of the equa- 

 tor, large basins of water exist, analogous to Lake Uniames 

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

 volcanoes, like the Demavend, near the Caspian Sea? Much 

 as the natives are accustomed to move about over the coun- 

 try, none of them have hitherto brought us the least notice 

 of any such thing ! 



IV. Asia. 



a. The Western and Central part. 



The volcano of Demavend,* in a state of ignition, but, ac- 

 cording to the accounts of Olivier, Morier, and Taylor Thom- 

 son (1837), smoking only moderately, and not uninterrupt- 

 edly. 



The volcano of Medina (eruption of lava in 1276). 



The volcano of Djebel el Tir (Tair or Tehr), an insular 

 mountain 895 feet high, between Loheia and Massaua, in the 

 Eed Sea. 



* The height of Demavend above the sea was given by Ainsworth at 

 14,695, but, after correcting a barometrical result probably attributable 

 to an error of the pen {Asie Centrale, t. iii., p. 327), it amounts, accord- 

 ing to Ottman's tables, to fully 18,633 feet. A somewhat greater ele- 

 vation, 20,085 feet, is given by the angles of altitude worked by my 

 friend Captain Lemm, of the Russian navy, in the year 1839, and 

 which are certainly very correct, but the distance is not trigonomet- 

 rically laid down, and rests on the presumption that the volcano of 

 Demavend is 66 versts distant from Teheran (one equatorial degree 

 being equal to 104-^ versts). Hence it would appear that the Persian 

 volcano of Demavend, covered with perpetual snow, situated so near 

 the southern shore of the Caspian Sea, but distant 600 geographical 

 miles from the Colchian coast of the Black Sea, is higher than the great 

 Ararat by about 2989 feet, and the Caucasian Elburuz by probably 1600 

 feet. On the Demavend, see Ritter, Erdkunde vonAsien, bd. vi., abth. 

 i., s. 551-571 ; and on the connection of the name Albordj, taken from 

 the mythic and therefore vague geography of the Zend nation, with the 

 modern name Elburz (Koh Alburz of Kazwini) and Elburuz, see 3id., 

 s< 43-49, 424, 552, and 555. 



