Page:EB1911 - Volume 23.djvu/926

 part, constitutes the frontier between European Russia and the Kirghiz steppe; it receives the Sakmara on the right and the Ilek on the left. The Kuma, the Terek and the Kura, with the Aras, which receives the waters of Lake Gok-cha, belong to Caucasia.

The soil of Russia depends chiefly on the distribution of the boulder-clay and loess, on the degree to which the rivers have

severally excavated their valleys, and on the moistness of the climate. Vast areas in Russia are quite unfit for cultivation, 19% of the aggregate surface of European Russia (apart from Poland and Finland) being occupied by lakes, marshes, sand, &c., 39% by, forests, 16% by prairies, and only 26% being under cultivation. The distribution of all these is, however, very unequal, and the five following subdivisions may be established:—(1) the tundras; (2) the forest region; (3) the middle region, comprising the surface available for agriculture and partly covered with forests; (4) the black-earth (chernozyom) region; and (5) the steppes. Of these the black-earth region—about 150,000,000 acres—which reaches from the Carpathians to the Urals, from the Pinsk marshes in the S.W. to the upper Oka in the N.E., is the most important. It is covered with a thick sheet of black earth, a kind of loess, mixed with 5 to 15% of humus, due to the decomposition of an herbaceous vegetation, which developed luxuriantly during the Lacustrine period on a continent relatively dry even at that epoch. On the three-fields system corn has been grown upon it for fifty to seventy consecutive years without manure. Isolated black-earth islands, though less fertile, occur also in Courland and Kovno, in the Oka-Volga-Kama depression, on the slopes of the Urals, and in a few patches in the N. Towards the Black Sea coast its thickness diminishes, and it disappears in the valleys. In the extensive region covered with boulder-clay the black earth appears only in isolated places, and the soil consists for the most part of a sandy clay, containing a much smaller admixture of humus. There cultivation is possible only with the aid of a considerable quantity of manure. Drainage finding no outlet through the thick clay, the soil of the forest region is often hidden beneath extensive marshes, and the forests themselves are often mere thickets choking marshy ground; large tracts of sand appear in the W., and the admixture of boulders with the clay in the N.W. renders agriculture difficult. On the Arctic coast the forests disappear, giving place to the tundras. Finally, in the S.E., towards the Caspian, on the slopes of the southern Urals and the plateau of Obshchiy Syrt, as also in the interior of the Crimea, and in several parts of Bessarabia, there are large tracts of real desert, buried under coarse sand and devoid of vegetation.

Notwithstanding the fact that Russia extends from N. to S. through 30° of latitude, the climate of its different portions, apart

from the Crimea and Caucasia, presents a striking uniformity. The aerial currents—cyclones, anti-cyclones and dry S.E. winds—prevail over extensive areas, and sweep across the flat plains without hindrance. Everywhere the winter is cold and the summer hot, both varying in their duration, but differing relatively little in the extremes of temperature recorded. There is no place in Russia, Archangel and Astrakhan included, where the thermometer does not rise in summer nearly to 86° Fahr. and descend in winter to -13° and -22°. It is only on the Black Sea coast that the absolute range of temperature does not exceed 108°, while in the remainder of Russia it reaches 126° to 144°, the oscillations being between -22° and -31°, occasionally going down as low as -54°, and rising as high as 86° to 104°, or even 109°. Everywhere the rainfall is small: if Finland and Poland on the one hand and Caucasia with the Caspian depression on the other be excluded, the average yearly rainfall varies between 16 and 28 in. Nowhere does the maximum rainfall take place in winter (as in W. Europe), but it occurs in summer, and everywhere the months of advanced spring are warmer than the corresponding months of autumn.

Though thus exhibiting the distinctive features of a continental climate, Russia does not lie altogether outside the reach of the moderating influence of the ocean. The Atlantic cyclones penetrate to the Russian plains, mitigating to some extent the cold of winter, and in summer bringing with them their moist winds and thunderstorms. Their influence is chiefly felt in W. Russia, though it does reach as far as the Urals and beyond. They thus check the extension and limit the duration of the cold anticyclones.

Throughout Russia the winter is of long duration. The last days of frost are experienced for the most part in April, but as late as May to the N. of 55° N. The spring is exceptionally beautiful in central Russia; late as it usually is, it sets in with vigour, and vegetation develops with a rapidity which gives to this season in Russia a special charm, unknown in warmer climates. The rapid melting of the snow at the same time causes the rivers to swell, and renders a great many minor streams navigable for a few weeks. But a return of cold weather, injurious to vegetation, is very frequently observed in central and E. Russia between May the 18th and the 24th, so that it is only in June that warm weather sets in definitely, and it reaches its maximum in the first half of July (or of August on the Black Sea coast). In S.E. Russia the summer is much warmer than in the corresponding latitudes of France, and really hot weather is experienced everywhere. It does not, however, prevail for long, and in the first half of September frosts begin on the middle Urals. They descend upon W. and S. Russia in the beginning of October, and are felt on the Caucasus about the middle of November. The temperature drops so rapidly that a month later, about October the 10th on the middle Urals and November the 15th throughout Russia, the thermometer ceases to rise above the freezing-point. The rivers freeze rapidly; towards November 20th all the streams of the White Sea basin are ice-bound, and so remain for an average of 167 days; those of the Baltic, Black Sea and Caspian basins freeze later, but about December the 20th nearly all the rivers of the country are highways for sledges. The Volga remains frozen for a period varying between 150 days in the N. and 90 days at Astrakhan, the Don for 100 to 110 days, and the Dnieper for 83 to 122 days. On the W. Dvina ice prevents navigation for 125 days, and even the Vistula at Warsaw remains frozen for 77 days. The lowest temperatures are experienced in January, the average being as low as 20° to 5° Fahr. throughout ussia; in the, west only does it rise above 22°. On the whole, February and March continue to be cold, and their average temperatures rise above zero nowhere except on the Black Sea coast. Even at Kiev and Lugañsk the average of March is below 30°, while in central Russia it is 25° to 22°, and as low as 20° and 16° at Samara and Orenburg.

All Russia is comprised between the isotherms of 32° and 54°. On the whole, they are more remote from one another than even on the plains of N. America, those of 46° to 32° being distributed over twenty degrees of latitude. They are, on the whole, inclined towards the S. in E. Russia; thus the isotherm of 39° runs from St Petersburg to Orenburg, and that of 35° from Torneå in Finland to Uralsk. The inflexion is still greater for the winter isotherms. Closely following one another, they run almost N. and S.; thus Odessa and Königsberg are situated on the same winter isotherm of 28°; St Petersburg, Orel and the mouth of the Ural river on about 20°; and Mezeñ and Ufa on 9°. The summer isotherms cross the winter isotherms nearly at right angles, so that Kiev and Ufa, Warsaw and Tobolsk, Riga and the upper Kama have the same average summer temperatures of 64°, 62½° and 61° respectively.

The laws and relations of the cyclones and anti-cyclones in Russia are not yet thoroughly understood. It appears, however, that in January the cyclones mostly travel across N.W. Russia (N. of 55° and W. of 40° E.), following directions which vary between N.E. and S.E. In July they are pushed farther towards the N., and cross the Gulf of Bothnia, while another series of cyclones sweep across middle Russia, between 50° and 55° N. Nor are the laws of the anti-cyclones established. The winds closely depend on the routes followed by both. Generally, however, it may be said that alike in January and in July W. and S.W. winds prevail in W. Russia, while E. winds are most common in S.E. Russia. N. winds are predominant on the Black Sea coast. The strength of the wind is greater, on the whole, than in the continental parts of W. Europe, and it attains its maximum velocity in winter. Terrible tempests blow from October to March, especially on the S. steppes and on the tundras. Hurricanes accompanied with snow (burans, myatels), and lasting from two to three days, or N. blizzards without snow, are especially dangerous to man and beast. The average relative moisture reaches 80 to 85% in the N., and only 70 to 81% in S. and E. Russia. In the steppes it is only 60% during summer, and still less (57) at Astrakhan. The average amount of cloud is 73 to 75% on the White Sea and in Lithuania, 68 to 64 in central Russia, and only 59 to 53 in the S. and S.E. The amount of rainfall is shown in the Table on next page.

The flora of Russia, which represents an intermediate link between the flora of Germany and the flora of Siberia, is strikingly uniform

over a very large area. Though not poor at any given place, it appears so if the space occupied by Russia be taken into account, only 3300 species of phanerogams and ferns 