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



From the above short sketch of the main orographical features of 

 Daghestan, we will proceed to trace the course of the four rivers 

 Koissu, a survey of which will help to give the reader a clear 

 notion of the conditions under which the transverse valley we are 

 now considering was formed. 



The most westerly, and at the same time the largest, of these four 

 streams, the Andian Koissu, passes first through the deep valleys in 

 the fundamental schists which divide the Katju range of mountains 

 from the main chain, and so far its course is entirely longitudinal. 

 The channel then bends to the N.E., and soon assumes a transversal 

 character, the valley traversing a plicated region of fundamental 

 schists and Lias, and at Konada passing into a tract of folded Jurassic 

 and Cretaceous rocks. In its lower section the channel is alternately 

 longitudinal and transversal ; in some places it cuts obliquely 

 through huge folds of Jurassic and Cretaceous strata (Malm to 

 Senonian), while at others it runs parallel with them. 



The two middle streams of the four, the Avarian Koissu and the 

 Kara-Koissu, have both eminently transversal courses, as is shown 

 indeed by their general N.N.E. direction, which is at right angles 

 to the prevailing strike-line of the stratification. In their upper 

 and intermediate sections these rivers flow over the fundamental 

 schists and form wide open valleys thickly set with hamlets. But 

 as soon as they enter the Jurassic and Cretaceous formations these 

 valleys become so constricted that they are scarcely habitable. This 

 is especially the case with the Kara-Koissu, the lower portion of 

 which, from Gunib, which is the centre of the government of the 

 district, forms a barren gorge cut in the plateaux of Malm-dolomite 

 and Neocomian limestone. Its only inhabited points are the military 

 stations at the bridges of Gunib and Salti. After this there is no 

 change of direction, as the river continues to cut at right angles 

 through the huge Malm and Neocomian formations, its channel 

 separating the plateaux of Gunib and Salti, which would otherwise 

 form an unbroken whole, and the mountains of Sochtala from those 

 of Koppa. 



Much the same state of things is to be seen in the course of the 

 Avarian Koissu, though its valley is not so narrow and impracticable 

 as that of its fellow river. It enters the flat Cretaceous and Jurassic 

 folds at a small angle, and then below Kara-Dagh traverses them 

 perpendicularly. 



The most easterly of the four branches, the Kumuch-Koissu, in 

 its upper course from Chosrek to Kasi-Kumuch, the centre of the 

 local government, has a N. 25° W. direction, which corresponds with 

 the general strike of the schists and sandstones over which it passes. 

 On both sides of the valley the strata fall to the E.S.E., the character 

 thus being that of an isoclinal valley. Lower down, near Kumuch, 

 where the river-channel enters the Jurassic and Cretaceous strata, it 

 partly cuts through the huge folds at a sharp angle and partly runs 

 parallel with them. 



If we now shortly summarize what I have just said, we shall 

 see that the four rivers Koissu have on the whole a course which 



