Trof. H. Sjogren — Valleys of the Caucasus. 395 



southern faces of these huge plateaux, all of which look towards 

 the main Caucasian chain, lie almost in a straight line with a 

 W. 25° N. direction, a line which marks the boundary, so important 

 in physiographical respects, between the upper and lower sections 

 of Inner Daghestan. While the average height of these plateaux is 

 about 6250 feet, the average height of the river beds which traverse 

 them is not more than some 2000 feet. To this great difference 

 of elevation is due the great difference between the climate and 

 products of the deep valleys and those of the high plateaux in this 

 region. 



The physiographical nature of the upper section of Inner 

 Daghestan shows a striking contrast to this. Here there are no 

 solid strata of limestone and dolomite, but only loose schists with 

 subordinate beds of sandstone belonging to the Lias formation or the 

 fundamental Caucasian schists. The high-lying plateaux, with their 

 precipitous cliffs, are no longer to be seen ; the river-valleys are 

 broader and more practicable ; the mountains slope less abruptly, 

 and their sides are modelled more softly by the ramifications of the 

 lines of erosion. 



We will now proceed to examine the structure of the chain of 

 mountains which encloses Inner Daghestan to the N. and N.E., and 

 give our special attention to that section through which the Sulak 

 has found a passage. 



On the whole the structure of the dividing ridge is very simple, 

 and for the greater part of its length it may be considered as an 

 oblique anticlinal fold or a system of several such folds. This at 

 least is its nature for a length of some 70 miles, from Bozrach in 

 the W. to Suluch-Dagh in the E. Throughout this stretch the ridge, 

 which consists entirely of Cretaceous rocks, forms a boundary as 

 well as a watershed between Inner and Outer Daghestan, and has 

 a mean elevation of nearly 6000 feet. The steeper side of the fold 

 lies throughout inside, i.e. it faces S. and S.W., while the strata of 

 the outer slopes show a gentler angle. A marked feature of this 

 particular section of the whole ridge is that the compression of the 

 fold has been more violent than in the adjacent sections, where there 

 has been less disturbance of the stratification. 



I may here repeat a passage from another paper of mine which 

 refers to the same region.^ " I have already shown, when treating 

 of the Cretaceous region of Daghestan, that the boundary between 

 the Outer and Inner divisions of the province is formed by a huge 

 ridge which belongs chiefly to the Senonian, though towards the 

 west the Neocomian also comes in. This watershed throughout a 

 great part of its length consists of an oblique fold. On the outer 

 slope the strata fall gently in angles of from 10° to 20°, on the 

 inner slope steeply, reaching from 60° to 90°." 



On the eastern slope of Salatau, immediately above the transverse 

 valley of the Sulak, the mountain is seen to be composed of three 

 of these oblique folds, lying one above the other. 



^ " Uebersicht der Geologie Daghestans und des Terek-Gebietes." Jahrb. d, k. k. 

 geol. Reichsanst. vol. 39, p. 434 (1889). 



