338 COSMOS. 



whom we are indebted for important supplements to the 

 Nubian geographers, has shown that the fires which burn on 

 the slope of the Cocaia have nothing volcanic in their nature. 

 (Asie Centrale, t. ii., p. 99.) Edrisi places the Lake of Te- 

 hania farther to the south. I think I have said enough to 

 show the probability of the Tehama being identical with the 

 great Lake of Balkasch, into which the Hi flows, and which 

 is only 180 miles farther south. A century and a half later 

 than Edrisi, Marco Polo placed the wall of Magog among 

 the mountains of In-schan, to the east of the elevated plain 

 of Gobi, in the direction of the River Hoang-ho and the Chi- 

 nese Wall, respecting which, singularly enough, the famous 

 Venetian traveler is as silent as he is on the subject of the 

 use of tea. The In-shan, the limit of the territory of Pres- 

 ter John, may be regarded as the eastern prolongation of the 

 Thian-schan (Asie Centrale, t. ii., p. 92-104). 



The two conical volcanic mountains, the Petschan and 

 Hotshen of Turfan, which formerly emitted lava, and which 

 are separated from each other at a distance of about 420 

 geographical miles by the gigantic block of mountains called 

 the Bogdo-Oola, crowned with eternal snow and ice, have 

 long been erroneously considered an isolated volcanic group. 

 I think I have shown that the volcanic action north and 

 south of the long chain of the Thian-schan here, as well as 

 in the Caucasus, stands in close geognostic connection with 

 the limits of the circle of terrestrial commotion, the hot- 

 springs, the solfataras, the sal ammoniacal fissures, and beds 

 of rock salt. 



According to the view I have already frequently express- 

 ed, and in which the writer most profoundly acquainted with 

 the Caucasian mountain system (Abich) now coincides, the 

 Caucasus itself is only a continuation of the ridge of the vol- 

 canic Thian-schan and Asferah, on the other side of the great 

 Aralo-Caspian depression.* This is, therefore, the place, in 

 connection with the phenomena of the Thian-schan, to cite 

 as belonging to pre-historical periods the four extinct volca- 

 noes of Elburuz, 18,494 feet in height; Ararat, 17,112 feet ; 

 Ivasbegk, 16,532 feet; and Savalan, 15,760 feet high.f In 



* Asie Centrale, t. ii., p. 9, and 51-58. See also p. 199, note *, of 

 the present volume. 



f Elburuz, Kasbegk, and Ararat, according to communications from 

 Struve, Asie Centrale, t. ii., p. 57. The height of the extinct volcano 

 of Savalan, westward of Ardebil, as given in the text, is founded on 

 a measurement of Chanykow. See Abich, in the Melanges Phys. ct 

 Chim., t. ii., p. 361. To save tedious repetition in the citation of the 



