LAKES AND EIYERS. 187 



St. Petersburg. It seems obvious that their progress northwards was checked by 

 the spongy nature of the soil, although this has partly been dried since the glacial 

 epoch. 



Finland and the neighbouring tracts, where the ice held its ground longest, 

 have remained largely lacustrine, the lakes in some places being more numerous 

 even than in Sweden. The dried land consists of isthmuses and narrow headlands, 

 and all the hollows and dej)ressions still remain filled with water. In this partly 

 flooded land are found the largest, but not the deepest, bodies of fresh water in 

 Europe — Ladoga, Onega, Saïma, Beyond this north-western territory lacustrine 

 basins occur here and there, but mostly already changed to peat beds and swamps. 

 Since the retreat of the ice, the river alluvia on the one hand, and the mossy 

 growths on the other, gradually encroaching on the waters, have had time to fill 

 in nearly all the lacustrine cavities, and all the more easily that the geological 

 formations of these districts lacked the resisting power of the Finland granites. 

 Thus have slowly disappeared such inland seas as that which formerly filled the 

 space now occupied by the Pripet marsh. Phenomena bearing witness to such 

 successive changes are everywhere visible — in lakes here merely encroached upon 

 by forests of reeds and turf banks, elsewhere reduced to a kind of tarn, " little 

 windows " {oJwchM) with moss-grown borders ; others, again, changed to bogs, or 

 already partly converted into grassy tracts, or invaded by stunted birch and pine 

 forests venturing on the marshy soil, and gradually drying it up. 



As the lakes shrink up and disappear, the rivers grow in importance. With 

 the exception of those of Finland, the Neva, and the Narova, all the great rivers of 

 Russia have acquired their fluvial character by draining the old lakes of their 

 basins. Owing to the vast spaces they have to traverse before reaching the sea, 

 they are fed by numerous afiluents and swollen to considerable volumes, which 

 seem all the more so in proportion to their sluggish currents. Some are of great 

 length, such as the Volga, exceeding all other European rivers in length, but not 

 in the abundance of its discharge, as is often asserted, being in this respect 

 surpassed by the Danube. The rainfall is far less copious than in the west of 

 Europe, exposed to the moist Atlantic winds, and cannot be estimated at more 

 than 20 inches during the year. In their lower course the streams flowing to the 

 Euxine, Sea of Azov, and Caspian traverse arid and treeless regions exposed to the 

 fierce rays of the sun, and to the fury of the steppe winds. Hence the evaporation 

 is here excessive, so that many rivers are absorbed by the soil and the air before 

 reaching their natural outlet. While ten times larger than France, Russia 

 possesses probably no more than three times the volume of its running waters. 

 The Volga itself is lost in the Caspian basin, where it is entirely evaporated 

 without raising the level of that inland sea, long cut ofi" from all communication 

 with the ocean. 



Pising in regions but slightly above the sea-level, the larger rivers are 

 nowhere separated from each other by elevated lands, and the chief obstacles to 

 intercommunication have not been the high water-partings, but the swamps, peat 

 beds, vast forests, and solitudes. The rivers themselves, while facilitating inter- 



