296 METEOEOLOGY IN RUSSIA. 



Dueper at Catlierinenslav, 48^^ , 91 



Dneper at Kherson, 46° 80 



Sosch at Gomel, 52° 122 



Berezina at Borissov, 54° , 129 



Pripet at Turov, 52° , 105 



Don at Ust-Medvedizo, 492 135 



Douat Aksai, 47^ 107 



Woroneje at Woroneje, 52° . . .- lo5 



Lopan at Charkov, 50° 127 



BASIN OF THE CASPIAN. 



Wolga at Tver, 56° 147 



Wolga at Yaroslav, 58° 152 



Wolga at Kostroma, 58° 161 



Wolga at Kasan, 50° 153 



Wolga at Samara, 53° 150 



Wolga at Saratov, 51° 132 



Wolga at Astrakhan, 46° 99 



Oka at Ore], 53° ... 130 



Jna at Tambov, 53° 140 



Kama near Dedjuchin 180 



Kama at Ussolje, 60° 176 



Kama at Perm, 58° 160 



Kama at Jelabuga, 56° 160 



Vjiitkaat Vjiltka, 58° 163 



Bjelaja at Ufa, 55° 158 



Ural at Orenburg, 51° 164 



BASIN OF THE ARAL SEA. 



Syr-Dariaat Khodjent, 40° 



Syr-Daria at Jt. Porovski, 45° , 98 



Syr-Daria at Kasalinsk, 46° 123 



The time of opening and closing of rivers depends not only on tlie 

 intensity and duration of frost, but also on many local conditions, as, for 

 example, the strength of the current. On this account the Angara at 

 Irkutsk is frozen only half the time it would be if its current were not so 

 very strong. This river very seldom freezes near Lake Baikal, and at 

 Irkutsk the freezing begins at the bottom. Elvers of such an exceptional 

 character are seldom met with in Eussia, as the greatest part of the 

 country is a level plain, only slightly undulating. There seems not to be 

 a very great difference in the time at which large and small ri\'ers are 

 frozen ; the former freeze and open a little later. Great and deep bodies 

 of water are not so easily cooled as small, and so great rivers freeze later. 

 The later opening in sjiring has a different cause : The ice of the smaller 

 rivers is broken by the inrush of water from melted snow. The channels 

 of great rivers do not fill so rapidly and their ice must l>e more worn 

 before it breaks. The Volga at Saratov, where it carries pu enormous 

 body of water, and the Oka at Orel, where it is a very small river, are 

 covered with ice nearly the same number of days. But the Volga is 

 frozen only from the 8th of December to the 19th April, wLile the Oka 



