F. GEOGEAPHY. 255 



duced from careful levelings, shows that for an altitude of 

 2000 feet, and on the average of seven days' observations, 

 the upper station is computed to be about eleven meters 

 (that is, about thirty-five feet) too high. What the individ- 

 ual discordances are from these mean results is not stated ; 

 but judging from the similar results given by Ruhlmann, we 

 are safe in saying that differences of altitude of 2000 feet 

 can not be determined by the barometer within a hundred 

 feet, unless the true temperature of the air is computed by 

 Plantamour's or Ruhlmann's method, and is used instead of 

 the observed temperatures directly given by thermometers. 

 App. JVo. 11 U. S. Coast Survey, 1871. 



DECREASE OF WATER IX EUROPEAN RIVERS IX THE PRESENT 



CENTURY. 



A suggestive paper has lately been communicated by Mr. 

 "W. G. Wex to the Geographical Society of Vienna upon the 

 decrease of water in rivers and sources. The author states 

 that the results of his observations tend to show the constant 

 decrease of the rivers of Germany and an increase of the seas. 

 They indicate that the levels of the German rivers are now 

 much lower than they were fifty years ago, the Elbe having 

 decreased to the amount of seventeen inches, the Rhine twen- 

 ty-four, the Oder seventeen, the Vistula twenty-six, and the 

 Danube fifty-five. The reason assigned for this is the pro- 

 gressing devastation of forests, which causes a decrease in 

 the atmospheric moisture they attract and convey to the 

 soil, and thence to sources of streams. 12 A, February 18, 

 1875,314. 



PHYSICAL PECULIARITIES OF THE UPPER VOLGA. 



According to Poljakow, who has been exploring the region 

 of the Upper Volga, under the patronage of the Russian Geo- 

 graphical Society, the Scandinavian Finlandic glacier, which 

 at one time covered the Government of Olonez and those ad- 

 jacent to it, must have stretched far into the basin of the 

 Volga and over the boundaries of the Waldai plateau; and 

 a connection must undoubtedly have existed between the 

 Arctic and Baltic seas by the unequal levels of the lakes 

 formed by the melting of the glacier, the slight remains of 

 which are seen in the existing lakes. 



