NA TURE 



541 



THURSDAY, OCTOBER 3, 1895. 



RITTER'S "AS/A": RUSSIAN ADDENDA. 



Eastern Siberia^ including Lake Baikal and the Moun- 

 tains on its Norlh-Western Shore. \'ol. II. By P. P. 

 Semenofif, I. D. Cherskiy, and G. (i. von Petz. Pp. 630. 

 (Russian: St. Petersburg, 1895.) 



THIS new volume, edited by P. P. Semenoff, from the 

 MS.S. of I. D. Cherskiy, and containing 630 pages 

 of text, in lieu of the three paragraphs of Hitters work, is 

 even more interesting than the preceding volume, which 

 was noticed in these columns a short time ago (Naturf., 

 vol. 1. p. 471). It covers Lake Baikal and the mountains 

 along its north-western shore, and embodied explorations 

 either entirely new or quite unknown even in Russia 

 itself Moreover, all that has been said concerning the 

 preceding volume, as regards the masterly treatment of 

 the subject and a strict adherence to Hitter's excellent 

 methods — a combination of a minute description of details 

 with broad generalisations drawn out of them — fully 

 applies to this new instalment of the great work under- 

 taken by the Russian Geographical .Society. A third 

 volume, containing Transbaikalia and the Gobi, will soon 

 follow — the invaluable collaboration of M. Obrucheff 

 having been secured for this purpose by the editor. 



When we cast a glance upon a good orographical map of 

 Asia (<•.,?■. Petermann's, in Sticler's '" Hand Atlas," or 

 even in the miniature "Taschen .\tlas " of the same pub- 

 lishers), we see that the two great plateaus of West and 

 East Asia are fringed along their north-western borders 

 with a chain of great lakes : the Caspian Sea, Lake 

 Balkhash, Ala-kul and Zaisan, Ulungur, Baikal, and 

 Oron ; while a succession of large post-Tertiary lakes, 

 now desiccated, which formerly filled the valleys of the 

 Tian-shan, the .'\ltais, the .Sayans, and the Muya ridges, 

 complete this chain of depressions along the outer border 

 of the plateaus. Lake Baikal is one of the lakes of this 

 chain — a small remainder only of the great mass of water 

 which formerly filled up the valley of the Irkut, and the 

 lower parts of the eastern tributaries of the present lake, 

 and discharged its waters, as we now learn from the 

 volume under review, through the narrow gorge pierced 

 by the Irkut through the Tunka .'Mps, by means of which 

 it now joins the Angara at Irkutsk. At that time, i.e. 

 during the post-Tertiary period, its level stood, as shown 

 l)y the lake deposits and terraces explored by Cherskiy, 

 .It least 928 feet above the present level of Lake Baikal, 

 which now lies 1561 feet above the sea level.' 



However, even in its present limits. Lake Baikal 

 occupies the sixth place among the largest lakes of the 

 globe (after Lake Tanganika), and the first place among 

 the .'\lpine lakes. Sufficient to say that it covers 15,300 

 square miles, and that the two extremities of the crescent 

 which it makes on a map are 380 miles distant from each 

 other. As for its depth it stands foremost. Already 

 Kononoffs soundings, in 1859, indicated a depth of 5621 



1 There is still a certain uncertainty, perhaps of over too feet, concernini; 

 the altitude of the level of Lake Baikal, .\ levelling across Siberia had been 

 m.ade a few years .aRO ; hut the death of the person who undertook the cal- 

 culation of the results brought about some confusion, and Russian geo- 

 graphers suppose that some considerable error may have crept in in the 

 levelling between the Yenisei and Irkutsk, and consequently in the above 

 figure. 



NO. 1353, VOL. 52] 



feet, and wheri the Polish exiles. Dr. Dybowski and 

 Godlewski, mad?, in 1867 and 1871-76, a series ofver)- 

 accurate soundings, they revealed the existence of several 

 valleys in its bottom, attaining depths of 2197, 4460, and 

 4503 feet, the greatest depths being located in the 

 proximity of the north-western shore, so that a depth of 

 1935 feet (374 feet below the level of the ocean) was found 

 within a thousand metres from the coast. 



Both in its position at the foot of, and the manner it 

 penetrates at its southern extremity into, the plateau. 

 Lake Baikal oflfers a striking analogy with the Caspian 

 Sea. The same analogy appears in its relations to the 

 surrounding mountains. It is divided about its middle 

 by a submerged ridge, which appears on the surface in 

 the Olkhon Island, and in the promontory of Svyatoi 

 Nos ; and of the two basins thus formed, and named 

 respectively the " Great Sea " and the " Small Sea," the 

 southern, that is the one which lies nearest to the plateau, 

 is the deepest. In older works, and in some recent ones 

 as well. Lake Baikal used to be described as a longi- 

 tudinal valley between two parallel chains of mountains ; 

 but it is evident, from what has just been said, 

 how false this view is. The next step would be 

 to consider it as originated from two lakes which 

 once occupied two longitudinal valleys, and joined 

 together after the dividing ridge had been partially de- 

 stroyed by geological agencies ; and this hypothesis, too, 

 has been advocated. Things appear, however, to be 

 much more complicated than that. When I was work- 

 ing out a general scheme of the orography of Siberia, I 

 was compelled to recognise that even the two-valleys- 

 hypothesis could not interpret the real features of the 

 region, and although at that time (1872) we knew next 

 to nothing about the geological structure of the Baikal 

 mountains, I was induced, by considerations about the 

 structure of the plateaus, their border-ridges, and the 

 .'Vlpinc chains parallel to the latter, to draw- two chains 

 across the northern part of the lake. From the volume 

 under review, we now learn the real state of affairs. In 

 all his explorations in .Siberia, Cherskiy used to pay a 

 great deal of attention to the orographical features as 

 they now appear to the explorer, and tried to discriminate 

 in how far they were a result of stnictural features — fold- 

 ings of the rocks and so on — and in how far they were 

 derived from subsequent erosion which has been going 

 on in these parts of Siberia since the Silurian and 

 Cambrian periods, when the mountain ridges and 

 plateaus received their first shape. As regards the 

 Baikal mountains, it now appears that there is, on the 

 north-western shore, a real ridge running parallel to the 

 shore, and separated by a valley from the mountains 

 lying further west ; but that both this ridge and the deep 

 hollow of the Baikal are due, not to structural, but to 

 erosion processes. The ridge consists of slates and 

 gneisses crossing it in a diagonal direction, and these 

 strata cross also the northern part of the lake in the 

 same direction — the direction I had indicated on the 

 orographical map on merely theoretical grounds — so as 

 to reappear in the same succession on the eastern shore. 

 The foldings of the Baikal Mountains date from the 

 Silurian, Cambrian, or perhaps even the Laurentian 

 period (Devonian red sandstones lie undisturbed at the 

 outer footings of the Baikal Mountains), but subsequent 



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