436 COSMOS. 



igneous mountain (Hot&cheu) of Turfan, from the shores of 

 the Polar Sea and the Indian Ocean, are almost equally great, 

 about 1480 and 1520 miles. On the other hand, the distance 

 of Pe-shan, whose eruptions of lava are separately recorded, 

 from the year 89 of our era up to the 7th century, in Chinese 

 works, from the great mountain-lake of Issikul to the descent 

 of the Temurtutagh (a western portion of the Thian-shan) is 

 only 172 miles, while from the more northerly situated lake 

 of Balkasch, 148 miles in length, it is 208 miles distant. 4 * 

 The great Dsaisang lake, in the neighbourhood of which I was 

 during my stay in the Chinese Dsungarei in 1829, is 360 miles 

 distant from the volcanoes of Thian-shan. Inland waters 

 are therefore not wanting, but they are certainly not in such 

 propinquity as that which the Caspian Sea bears to the still 

 active volcano of Demavend in the Persian Mazenderan. 



While, however, basins of water, whether oceanic or in- 

 land, may not be requisite for the maintenance of volcanic 

 activity, yet, if islands and coasts, as I am inclined to 

 believe, abound more in volcanoes only because the elevation 

 of the latter, produced by internal elastic forces, is accom- 

 panied by a neighbouring depression in the basin of the sea, 45 

 so that an area of elevation borders on an area of depres- 

 sion, and that at this bordering-line large and deeply pene- 

 trating fissures and rents are produced, it may be supposed 

 that in the central Asiatic zone, between the parallels of 

 41 and 48, the great Aralo-Caspian area of depression, as 

 well as the large number of lakes, whether disposed in ranges 

 or otherwise, between the Thian-shan and the Altai-Kurts- 

 chum, may have given rise to littoral phenomena. We know 

 from tradition that many small basins now ranged in a row 

 like a string of beads (lacs a chapelet} once upon a time 

 formed a single large basin. Many large lakes are seen to 

 divide and form smaller ones from the disproportion be- 

 tween precipitation and evaporation. A very experienced 

 observer of the Kirghis Steppe, General Genz of Oren- 

 burg, has conjectured that there formerly existed a water- 



44 See above, p. 358. 



45 See Arago, Sur la cause de la depression d'une grande partie 

 de 1'Asie et sur le phenomene que les pentes les plus rapides des 

 chaines de montagnes sont (ge'ueralement) tourne'es vers la r 



plus voisine, in his Astronomie Populaire, t. iii. pp. 12661274. 



rner la 



