392 I'rof. H. Sjogren — Valleys of the Caucasus. 



appear that, owing to the abstraction of water required to form the 

 ice, the surface of the sea would on the whole be lowered, and this 

 effect would surpass the other, however great the thickness of ice, 

 so that the combined effect of the European and North American 

 glaciations, if simultaneous, would be to cause a general sinking of 

 the sea-level during the period of maximum ice. The general 

 result, howevisr, would depend much upon the relative extent of the 

 Arctic and Antarctic glaciers at the time, a subject regarding which 

 we know little or nothing. Penck seems to have been under the 

 impression that the attraction would have caused the sea to rise 

 towards the border of the ice in a comparatively rapid swell, but 

 such would not have been the case. Any rise in the level of the 

 sea induced by such a cause woiild be nearly parallel to the present 

 surface, and would extend much further horizontally outwards than 

 Penck seems to have contemplated, while its vertical extent would 

 be far less than he supposed. 



If at the commencement of the Glacial period, Scandinavia (or 

 at least a large part of it) stood several thousand feet higher than 

 it does now, then it follows that the subsequent depression must 

 have been very considerable indeed, and the subsidence of such 

 a large area to the extent required would no doubt occasion much 

 squeezing, disturbance, and probably some upheaval in neighbouring 

 regions. I am inclined to think that the ice was gathering on the 

 mountains of Norway at a much earlier period than is generally 

 believed, and that the coming on of the glaciation took place ia 

 early Pliocene times, or even sooner. Many of the disturbances 

 that have taken place in the strata near the Straits of Dover and 

 elsewhere may have been occasioned by strains induced by the load 

 of ice, and the bursting out of volcanoes in Germany, Auvergne, 

 and other places may have arisen from pressure on the subterranean 

 lava due to the same cause. 



III. — Transverse Valleys in the Eastern Caucasus. 



By Professor Hjalmak, Sjogren, 

 Professor of Mineralogy and Geology in the University of Upsala, Sweden. 



1. The Sulah gorge below Gimri in Daghestan. 



AMONG the many valleys of Daghestan that are interesting to 

 the geologist there are none more remarkable than the channel 

 by which the river Sulak passes through the chain of Cretaceous 

 and Jurassic mountains which borders Inner Daghestan. Just above 

 the entrance of this defile the four rivers Koissu unite in one stream, 

 which in a series of cataracts tears through a stupendous chasm 

 some fifteen miles in length, cutting the huge ridge almost at right 

 angles to its axis. 



The gorge traverses the main chalk ridge in the direction N. 40° 

 E., then changes its line to N.W., which it still follows at the 

 widening of the valley below Tjirkei, and finally comes back to due 

 N. as it passes through the Tertiary hills below Subut. The mean 

 height of the ridge thus cut asunder is some 2000 metres or more 



