383 



states that he has already ascertained it to extend over at least 

 18,000 square leagues, reaching to Saratof, Orenburg, and the 

 low regions of the Oxus and Jaxartes. This great basin, the 

 lowest level of which is about three hundred feet below the Medi- 

 terranean, is filled with tertiary deposits ; and, according to the 

 speculations of M. de Humboldt, is supposed to have been formed by 

 a subsidence, accompanying the elevation of the great table-land of 

 Teheran, whilst the Oural mountains, which traverse the depression 

 from north to south are referred to a more ancient period. 



By consulting these volumes you will find valuable information 

 not only respecting the frigid climate of central Asia, as determined 

 by the great mass of land and other geological causes ; but you will 

 learn that the metallic veins in the Oural occur only on its eastern 

 flank, and that remains of large extinct mammalia have recently 

 been found on the very summits of the chain. 



Another part of Asia has lately been explored. The Russian Go- 

 vernment, with its characteristic enterprise, being desirous of ac- 

 quiring accurate information respecting the structure, natural 

 history and heights of the Caucasus, sent thither in the summer of 

 1829, under a strong escort commanded by General Emanuel, a 

 party of men of science, the chief of whom, M. Kupffer, has given 

 in his report to the Academy of Sciences of St. Petersburg. 



From the geographical and geological chapters of this interesting 

 report, we learn, that the low hills which rise above the steppes of 

 the Black Sea and Sea of Azof, are composed of limestone filled with 

 littoral shells, the collections of which made by M. Pander, on this 

 and on a former occasion, must prove of great geological importance. 

 On ascending from the steppes towards the Caucasus, grits and older 

 limestones with Ammonites occupy an undulating country, diversi- 

 fied by several peaks of trachyte, the principal of which, the Bechtav, 

 or Five Mountains, is stated to be 4,000 feet above the sea. The 

 outer zone of the Caucasus is described as being a rugged and lofty 

 plateau, from 8,000 to 9,000 feet above the sea, the strata of which 

 present tabular summits, chiefly composed of calcareous grit and 

 conglomerates nearly horizontal, or rising at only a gentle angle 

 towards the central ridge. This table-land is fissured by deep, trans- 

 verse rents, in which the rivers flow ; and one of the lowest forma- 

 tions is a limestone, which the author compares with the cal- 

 caire d, gryphites. These secondary strata are separated from the 

 central mountains by a band of transition and old slaty rocks, which 

 have been dislocated by the contact of certain green-stones and 

 basalts. The loftiest part of the central chain, culminating in the 

 double peak of Mount Elbruz at the height of 15,400 French feet 

 above the Black Sea, is entirely of igneous origin, being principally 



boldt, is now engaged in directing surveys and barometrical "soundings," 

 as they are emphatically styled, by which the precise extent, depths, 

 and true shore of this dry Caspian will be accurately defined. 



