The universal geography : earth and its inhabitants

424 RUSSIA IN EUBOPE.connecting the Don by canal with the Volga. The average volume of water isdoubtless sufficient to feed a canal, for Belelubski estimates it at 8,650 cubic feetper second ; but the quantity varies greatly with the floods and dry seasons. Freefrom ice for about two hundred and forty days at its easternmost bend, the Don issometimes so low and blocked with shoals that navigation becomes difficult even forflat-bottomed boats.During the two floods, at the melting of the ice in spring and inthe summer rains, its lower course rises 18 to 20 feetabove its normal level, overflowingits banks in several places for a distance of 18 miles.But in its irregularityFig. 220. Isthmus between the Don and Volga.Scale 1 : 940,000.eo-EL.ofCits flow resembles that of a mountain torrent. Some of its affluents also almost rundry in summer. In fact, the valleys and ovrags, or water-courses, of South Bussia. areprecisely of the same character as the wadies of certain arid lands in Asia and Africa,the streams of the ovrags being classed as " dry " and " wet," while even the latterare mostly mere rivulets, finding their way with difficulty across the argillaceoussoil.Nevertheless the wells sunk 160 to 260 feet deep yield everywhere an abundanceof good water.The most important, although not the most extensive, coal-fields of Bussia coveran area of about 10,000 square miles, chiefly in the southern part of the Donetz