INFLUENCE OF SNOW-MASSES ON CLIMATE. 65 



frosts, and permit the safe continuance of navigation during tardy 

 winters. 



In all countries where the snow forms deep masses in winter, the 

 rivers rise at the time of its melting ; the quantity of water pro- 

 duced hy the melting of snow and ice is so great, and the evapora- 

 tion is so little, as to produce much greater floods than ever can arise 

 from rains. This phenomenon is therefore of a character to affect some 

 of the sides of practical life ; yet the way in which it operates has 

 never been sufficiently well observed. The results of the thaw depend 

 upon its rapidity as well as upon the quantity of snow that may be 

 upon the ground when the frost breaks up. If the snow melts rapidly, 

 inundations may ensue, while the duration of the high water will be 

 too brief for it to be utilized for navigation ; and the contrary will 

 take place if the thaw is slow and gradual. 



It is a popular saying in Russia that when there is little snow the 

 waters will be high, and there will be little water when much snow 

 falls. This kind of paradox is justified in the case of the smaller 

 rivers. When little snow falls in winter, the ground freezes to a 

 great depth. The first water that is spread over the surface also 

 freezes, and a crust of ice is formed, over which the water flows as 

 over a rock, without penetrating it. It therefore reaches the rivers 

 quickly and swells their waters. When, on the contrary, the snow is 

 abundant, it protects the ground in such a way that the thaw can 

 begin from below, and the formation of a crust of ice on the surface 

 is not possible. The melted snow penetrates the soil, and does not 

 reach the ravines and rivers till after some time that is, till after the 

 ground has been saturated. The Russian peasants call this ground- 

 water. Observation teaches that it proceeds from the forests rather 

 than from the fields, because the snow accumulates there to a greater 

 depth, and is less scattered by the winds than in open places. 



The melting of snow from below was observed in 1884, at the 

 Agricultural Academy of Petrovsky, near Moscow. Observations 

 were made at the surface and at various depths down to two metres. 

 At seventy-five centimetres the temperature reached the freezing-point 

 on the 5th of March, and it rose to a greater height sooner from this 

 point than at fifty or at twenty-five centimetres. As similar conditions 

 have been observed at various points in the valley of the Volga, the 

 high waters of that river in 1884 did not rise above the mean, notwith- 

 standing the great depth of the snow ; but the sources of the stream 

 were so well supplied with water by the gradual melting of the snow 

 that navigation was unimpeded during the whole of the summer and 

 fall. The contrary took place in 1880, when a colder winter with less 

 snow was favorable to a rapid thaw ; the freshets were among the 

 highest that had been observed, but the water soon fell off, and from 

 August till October navigation everywhere above the mouth of the 

 Kama was precarious. 



VOL. XXXI. 5 



