146 



NA TURE 



[December 19, 1901 



movements which are recorded in the roclcs ; the positive 

 movements appear to last much longer than the negative 

 movements which follow them. From the Rhiutic to the 

 Callovian in Europe there was an encroachment of the 

 sea upon the land subject only to minor regressions, but 

 the succeeding negative phase which is marked by the 

 Portlandian and Purbeckian was of comparatively short 

 duration. 



How are these slow positive movements to be accounted 

 for? The deposition of sediment necessarily tends to 

 produce a continual rise of the sea-level. The formation of 

 the Black Sea and the .Egean Sea, as we have pointed out, 

 would account for a general lowering of the sea-level to 

 the extent of 4 metres ; but to produce a corresponding 

 movement in the opposite direction by denudation and 

 deposition would require the transference of an amount 

 of solid rock equivalent to the lowering of the general 

 surface of the land by as much as 10 metres. 



The author, however, hesitates to draw the conclusion 

 that the principal positive movements are the result of 

 this cause, and favours the idea that, in some unknown 

 manner, the waters of the ocean have been alternately 

 heaped up at the equator and the poles. 



We turn now to the volume which forms the more 

 immediate subject of this review. It deals mainly with 

 those portions of Asia on which so much light has been 

 thrown during the last decade by the indefatigable 

 researches of Russian geologists ; the method of treat- 

 ment is that with which all readers of the first two volumes 

 are familiar. Broad generalisations are suggested in a 

 few words, and then follows a mass of local detail which 

 it is impossible to understand fully without better maps 

 than those which illustrate the work or which are to be 

 found in any ordinary atlas. We look forward with 

 interest to the publication of the French translation, for 

 in the matter of maps and illustrations the French editions 

 of the first two volumes are superior to the original 

 German work. We owe a deep debt of gratitude to 

 M. Margdrie and the other distinguished French geo- 

 logists who have taken so much pains in the translation 

 of this remarkable work and in the selection of additional 

 maps and illustrations. 



Different observers have taken different views as to the 

 structure of .Vsia, but all are agreed as to the existence of 

 a certain uniformity of plan. Prof Suess calls attention 

 to the predominance of bow-like forms. Such forms are 

 seen on the shores of the Pacific and in the festoon-like 

 arrangement of the adjacent islands, on the Ganges, the 

 Indus and in Iran. The bows may be strongly or weakly 

 bent, crowded together or separated from each other, but 

 they are always arranged in such a way as to suggest a 

 relation to some central nucleus. This nucleus the author 

 finds in the neighbourhood of Irkutsk and Lake Baikal. 

 It is a region of .\rch;L-an gneisses and schists which has 

 been broken up into "horsts" and "sinkings." The 

 great amphitheatre of Irkutsk which is drained by the 

 Angara forms a notch in " the old nucleus " (der alte 

 Scheitel). It has been formed by sinking and is bordered 

 by powerful faults. 



.As the nucleus is approached, the forms of the moun- 

 tains change. In the neighbourhood of the sea volcanoes 

 occur; further inwards the snow-clad peaks of the giant 

 mountains form the dominant features ; to these succeed 

 NO. 1677, VOL. 65J 



the rock-walls of the Gobi, which rise above the lower 

 ground formed of horizontally stratified deposits. From 

 the Altai to the region south of Lake Baikal and 

 onward to the Upper Amur, the features are character- 

 istic of an old mountain land which has been more or 

 less completely worn down by denudation. The moun- 

 tains here ha\e rounded summits, and rest on broad 

 bases. The river systems are fully developed, and when 

 rapids occur they can be traced to comparatively recent 

 changes, such as the outpouring of basalt. These are the 

 characteristic features of the old nucleus. To the north 

 of this nucleus the elevations are tabular and are often 

 formed of flat-lying Pahcozoic strata capped by later 

 basalts. In the tundra region of the extreme north, 

 marine horizontal strata give evidence of the Mesozoic 

 transgression. 



So far we have been referring only to the introduction. 

 The second section deals with .Siberia, which is divided 

 into two well-marked areas, the west Siberian plain and 

 the east Siberian tableland. The only eminences which 

 rise above the alluvial flats in the western plain, between 

 the Yenesei and the Obi, are relics of a once extensive 

 sheet of soft Tertiary sandstone. The Middle Jurassic 

 transgression, which is traceable from the Arctic regions 

 over the Petcbora to Cracow, extends from Russia 

 through the low grounds of Turan to Baluchistan and 

 round the shores of the Indian Ocean, but has not as yet 

 been recognised in western Siberia. The only traces of 

 the widespread Upper Cretaceous transgression occur 

 in western Siberia at .Ajat, in the south-west corner. 

 Marine deposits with characteristic European fossils here 

 lie on folded Pahcozoic strata. 



The Tertiary seas (Upper Eocene and Lower Oligocene) 

 gained access to Siberia through the .Straits of Turgai 

 (south of the Urals), and reached as far as Semipalatinsk 

 and Sosswa. About the middle or end of the Oligocene 

 period, all connection with the European seas was cut 

 off and the flora of the amber forests spread over the 

 regions vacated by the sea. This great negative move- 

 ment led to the isolation of oceanic areas both in Europe 

 and Asia, and to the formation of extensive salt-deposits. 



The east Siberian tableland is bounded on the south 

 by the old nucleus, on the north-east by the bow of the 

 Werchogan Mountains, on the north-west by the 

 mountains of the Taimyr Peninsula and on the north by 

 the frozen sea. The Lena belongs to the tableland, and 

 flows in a valley which is often 300 metres deep. Four 

 elements take part in the structure of this plateau region. 

 The first is the Pahi^ozoic floor, which probably underlies 

 the whole. The lowest beds belong to the Olcuclliis 

 zone. They are horizontal except on the borders of 

 the amphitheatre of Irkutsk. This amphitheatre has 

 already been referred to as a sunken portion of the old 

 nucleus which is bordered by powerful faults. Folding 

 and even overfolding are associated with these faults, and 

 the direction of overfolding, as so frequently happens 

 under similar circumstances, is directed towards the 

 centre of the sunken tract. 



The second element consistsof plant-bearing beds, which 

 often contain workable coal. Asplciiiitm wliithyense is 

 common, and the deposits were referred by Heer to the 

 Middle Jura. The rocks are sandstone and conglo- 

 merate. Plant-bearing beds of the same general type 



