Page:EB1911 - Volume 23.djvu/915

 level of the Miocene sea, which was very shallow to the N. of this last ridge, while farther S. it was connected both with the Vienna basin and with the Aral-Caspian. The Pliocene appears only in the coast region of the Black and Azov Seas, but it is widely developed in the Aral-Caspian region, where, however, the Ust-Urt and the Obshchiy Syrt rose above the sea.

The thick Quaternary, or Post-Pliocene, deposits which cover nearly all Russia were for a long time a puzzle to geologists. They consist of a boulder clay in the N. and of loess in the S. The former presents an intimate mixture of boulders brought from Finland and Olonets (with an addition of local boulders) with small gravel, coarse sand and the finest glacial mud,—the whole bearing no trace of ever having been washed up and sorted by water in motion, except in subordinate layers of glacial sand and gravel; the size of the boulders decreases on the whole from N. to S., and the boulder clay, especially in N. and central Russia, often takes the shape of ridges parallel to the direction of the motion of the boulders. Its S. limits, roughly corresponding with those established by Murchison, but not yet settled in the S.E. and E., are, according to M. Nikitin, the following:—from the S. frontier of Poland to Ovrutch, Umañ, Kremenchug, Poltava and Razdornaya (50° N. latitude), with a curve N. to Kozelsk (?); thence due N. to Vetluga (58° N. latitude), E. to Glazova in Vyatka, and from this place towards the N. and W. along the watershed of the Volga and Pechora (?). S. of the 50th parallel appears the loess, with all its usual characters (land fossils, want of stratification, &c.), showing a remarkable uniformity of composition over very large surfaces; it covers both watersheds and valleys, but chiefly the former. Such being the characters of the Quaternary deposits in Russia, the majority of Russian geologists now adopt the opinion that Russia was covered, as far as the above limits, with an immense ice-sheet which crept over central Russia and central Germany from Scandinavia and N. Russia. Another ice-covering was probably advancing at the same time from the N.E., that is, from the N. of the Urals, but the question as to the glaciation of the Urals still remains open. As to the loess, the usual view is that it was a steppe-deposit due to the drifting of fine sand and dust during a dry episode in the Pleistocene period.

The deposits of the Post-Glacial period are represented throughout Russia, Poland and Finland, as also throughout Siberia and Central Asia, by very thick lacustrine deposits, which show that, after the melting of the ice-sheet, the country was covered with immense lakes, connected by broad channels (the fjärden of the Swedes), which later on gave rise to the actual rivers. On the outskirts of the lacustrine region, traces of marine deposits, not higher than 200 or perhaps even 150 ft. above present sea-level, are found alike on the Arctic Sea and on the Baltic and Black Sea coasts. A deep gulf of the Arctic Sea advanced up the valley of the Dvina; and the Caspian, connected by the Manych with the Black Sea, and by the Uzboy valley with Lake Aral, penetrated N. up the Volga valley, as far as its Samara bend. Unmistakable traces show that, while during the Glacial period Russia had an arctic flora and fauna, the climate of the Lacustrine period was more genial than it is now, and a dense human population at that time peopled the shores of the numberless lakes.

The Lacustrine period has not yet reached its close in Russia. Finland and the N.W. hilly plateaus are still in the same geological phase, and are dotted with numberless lakes and ponds, while the rivers continue to dig out their yet undetermined channels. But the great lakes which covered the country during the Lacustrine period have disappeared, leaving behind them immense marshes like those of the Pripet and in the N.E. The disappearance of what still remains of them is accelerated not only by the general decrease of moisture, but also perhaps by the gradual upheaval of N. Russia, which is going on from Esthonia and Finland to the Kola peninsula and Novaya Zemlya, at an average rate of about two feet per century. This upheaval—the consequences of which have been felt even within the historic period, by the drainage of the formerly impracticable marshes of Novgorod and at the head of the Gulf of Finland—together with the destruction of forests (which must be considered, however, as a quite subordinate cause), contributes towards a decrease of precipitation over Russia and towards increased shallowness of her rivers. At the same time, as the gradients are gradually increasing on account of the upheaval of the continent, the rivers dig their channels deeper and deeper. Consequently central and especially S. Russia witness the formation of numerous miniature cañons, or ovraghi (deep ravines), the summits of which rapidly advance and ramify in the loose surface deposits. As for the S. steppes, their desiccation, the consequence of the above causes, is in rapid progress.

Population.—The population of the empire, which was estimated at 74,000,000 in 1859, was found to be over 129,200,000 at the census of 1897, taken over all the empire except Finland. In 1904 it was estimated to be 143,000,000, and in 1906, according to a detailed estimate of the Central Statistical Committee, it was 149,299,300. Thus from 1860 to 1897 the population increased 74½%, and from 1897 to 1904 26.3, an average annual increase of about 3½% as compared with an average annual increase of 2¾% during the period 1860-97. The increase took place chiefly in the large cities, in Siberia, Poland, Lithuania, S. Russia and Caucasia. The official divisions of the empire are given here, and details are given in separate articles.

It has been found, from a comparison of the densities of population of the various provinces in 1859 with the distribution in 1897, that the centre of density has distinctly moved S., towards the shores of the Black Sea, and W., the greatest increase having taken place in the E. Polish and in the Lithuanian provinces, along the S.W. border, in the prairie belt beside the Black Sea, and in Orenburg. N. Caucasia and S.W. Siberia likewise show a considerable increase. The census of 1897 revealed in several provinces a remarkably low proportion of men to women. This was owing to the fact that large numbers of the men engaged in agricultural pursuits during the summer temporarily move every year into the large industrial centres for the winter. Consequently there were only 87.4 and 89.8 women to every 100 men in the governments of St Petersburg and Taurida respectively, but as many as 133.8 in Yaroslavl, 119 in Tver and 117 in Kostroma. The average number of women to every 100 men in the Russian governments proper was 102.9; in Poland, 98.6; in Finland, 102.2; in Caucasia, 88.9; in Siberia, 93.7; and in Turkestan and Transcaspia, 83.0.