Volcanoes of Central Asia. 1 47 



square leagues, and which lies between the Kooma, the Don, the 

 Volga, the Yak, the Obsheysyrt, lake Aksakal, the Lower Sihon, 

 and the Khanat of Khiva, upon the shores of the Amoo-daria, 

 is situated below the level of the ocean. The existence of this 

 singular depression has been the object of laborious barometrical 

 observations of levels between the Caspian Sea and the Black 

 Sea, by MM. Parrot and Engelhardt; between Orenburg and 

 Gouriev at the mouth of the Yaik, by MM. Helmersen and 

 Hoffmann. This very low country is abundant in tertiary forma- 

 tions, whence proceeds melaphyre, and debris of scorified rocks, 

 and off*ers to the geognostic inquirer, from the constitution of its 

 soil, a phenomena hitherto unique in our planet. To the south 

 of Baku, and in the Gulf of Balkan, this aspect is materially 

 modified by volcanic forces. The Academy of Sciences of St 

 Petersburgh has recently complied with my solicitations to get 

 determined by a series of stations of barometric levels upon 

 north-eastern edge of this basin, upon the Volga between Kamy- 

 shin and Saratov, upon the Yaik between the Obsheysyrt, Oren- 

 burg, and the Uralsk, upon the Yemba and beyond the hills of 

 Mougojar, by which the Ural extends itself towards the south 

 on the side of lake Aksakal and towards Sarasu, the position of 

 a geodoesic line, uniting all the j)oints at the level of the surface 

 of the ocean. 



I have referred already to the hypothesis, according to which 

 this great depression of the land of Western Asia was formerly 

 continued as far as the mouth of the Ob and the Frozen Sea, by 

 a valley traversing the desert of Kara-koum and the numerous 

 groups of oases in the steppes of the Kirghiz and Baraba. Its 

 origin appears to me to be more ancient than that of the Ural 

 mountains, the southern prolongation of which may be traced in 

 an uninterrupted course from the table-land of Gaberlinsk to 

 Oustoort, between lake Aral and the Caspian Sea. Would not 

 a chain, whose height is so inconsiderable, have entirely dis- 

 appeared if the great rent of the Ural had not been formed 

 subsequently to this depression ? Consequently, the period of 

 the sinking of Western Asia coincides rather with that of the 

 rising of the table-land of Iran, that of Central Asia, the Hima- 

 laya, the Kwan-lun, the Teen-shan, and all the old systems of 

 mountains running from east to west ; perhaps also with the 



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