550 . GEOLOGICAL MEMOIRS; 



II. On the Geology of the Altai Mountains. By M. de Tciiihat- 



cheff. 



[Communicated at the meeting of the French Geological Society at Chambery in 

 1844.* Vide Bui. dela Soc. Geol. de Fr. 2rrie ser. torn. i. p. 674.] 



The district of the Altai mountains, as described by M. Tchihat- 

 cheff, is situated in Central Asia, between latitude 49° and 

 52° 30' N., and longitude 79° and 86° 20' east of Paris, and is de- 

 scribed as extending for about 500 miles in one direction, by 220 

 in the other. It abounds in lofty mountain peaks, and is traversed 

 by vast rivers, the length of whose course is only surpassed by 

 that of the Amazons, and the Mississippi in America, the Yang- 

 Tse in Eastern Asia, and the Nile in Africa. Of these rivers the 

 Ob is the principal, and it is fed by a number of very considerable 

 streams, almost all of which exhibit a striking contrast in the 

 relative level of their two banks, the height of the right bank being 

 considerably greater than that of the left.f 



The direction of the principal streams which traverse the Altai 

 district exhibits a general agreement with that of the mountain 

 chains, and also with the strike of the different groups of strata. 

 Combining the observations that have been made with regard to 

 these points, the whole tract may be subdivided into two districts, 

 the western and the eastern, the former extending between the 

 river Ob and the northern zone of the river of Katoune, in which 

 the prevailing direction of the mountain chains is N. W. and S. E., 

 and the latter including the central and southern district of the 

 river of Katoune, and extending to the borders of the Sayanes, the 

 direction of the mountain chains in it gradually altering from that 

 in the former district, and terminating by running from N. E. to 

 S. W. It is interesting to find that this change in the direction of 

 the mountain chains is accompanied by marks of disturbance in the 

 folds and contortions of rocks, and by the appearance of curved 

 and broken lines of high ground, which are very strikingly shown, 

 and are, indeed, evident by a mere glance at the map of the dis- 

 trict. In the steppe of Tchouya this arrangement of a series of 

 heights in the form of a natural amphitheatre takes place in rocks 

 composed of clay slate, and all the masses, shaped into the form of 

 gigantic craters, or of lofty crests, folded as it were back upon one 

 another, and strikingly resembling the configuration of igneous 



* The observations of M. Tchihatcheff, the results of which were communi- 

 cated in this notice to the French Geol. Soc, were also offered to the Academy 

 of Sciences, and a report on the subject by Messrs. Brongniart, Dufresnoy, and 

 Elie de Beaumont appears in the " Comptes Rendus " of the 12th of May 

 (vol. xx. p. 1389). We learn, also, from a late number of the Bulletins de la 

 Soc. Geol. de France," that M. Tchihatcheff has now published his great work, 

 of which the outlines are here given. — En. 



| This is the case too with the rivers in Northern Siberia, and also with 

 the Volga and others of European Russia. See " Russia and the Ural Moun- 

 tains," by Mr. Murchison, M. de Verneuil, and Count Kevserling, vol. i. p. 650. 

 — En. 



